Bottlehead Forum
Bottlehead Kits => Legacy Kit Products => Topic started by: debk on June 04, 2012, 07:54:55 AM
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I am thinking of building the SR45 amplifier from the schematic that is posted elsewhere.
Are the boards that were used in the upgrade kit still available? I can get the components elsewhere, but I would prefer not to have to design boards for the project.
From what I have read this was a fantastic sounding amp. How does it compare to the Paramounts modified for 45's
Thanks
Debra
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I haven't done a 45 Paramount. There would be the advantage of direct coupling over the original SR45 however it wouldn't have the shunt regulated output stage. So it's hard to say which you might like better. I'm thinking it might be possible to do an SR45 on a Stereomour chassis. If it's feasible and there is enough interest perhaps we could do another limited run for advanced builders who don't need dot to dot instructions (we can't justify taking many man hours to write a step by step manual for a product that we might only make five or six copies of). At any rate, yes, I'm sure we have PC boards that could be used for the purpose.
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The original SR45 used the PT-2 power transformer, long since out of production. That transformer had the 2.5v heater winding.
I always thought that the refinement of a fully shunt regulated 45 amp was compromised by the hum from the AC heater supply. I do have sketches and notes in development for a more modern version with DC heater supply. The critical PC board is the current source feeding the shunt regulator, and I am revising the Crack Speedball board to cover such an application (and to use a slightly larger heat sink). That board should be in production in a few months if things go as currently planned. This summer looks like a good time for prototyping!
In both designs, the driver is cap-coupled. At the time, we thought (and I for one still think) that the advantage of shunt regulation is greater than that of direct coupling, especially if you are using really high quality coupling caps (teflon V-caps are I believe still at the top of the list). Direct coupling pushes the power supply voltage higher, to beyond the ratings of currently available the solid-state components in the shunt reg and current source. At that point, the safety issues get really hairy too, so I haven't looked into the necessary re-design issues.
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Small correction - Eileen has just advised that the PT-2 can be had, for a price, in small quantities.
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Sounds like this could happen :). Hopefully we can keep the interest up!
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If I were to build this I would like to do it with DC heater supply. I am sure I can get a power transformer from the usually sources or have one wound that will work.
I am in no hurry, having just built a pair of 300b DRD amps, but am I am interested in getting a couple of the boards when you have them available.
Thanks
Debra
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The version I built, single chassis and power supply, like a Stereomour. As to hum I use AC and have inaudible hum. I centered the hum pots when I wired them up and have never needed to adjust them.
One thing I did. 2.5V transformers were out of stock when I built mine, so I took a 5V Hammond with a center tap and did a little surgery. turns out it is 2 separate windings, joined at one end to make the tap. I separated them to make 2, 2.5V windings on a common core. not sure if this bucks the hum or not.
I would try AC first, unless you have 100db speakers, I don't think you need it
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I will most likely be using these with Orca's
Debra
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I'd be interested either in PT-2s or complete Paramour kits to be built as SR45s
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I too would be interested in the transformers
Debra
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Debra,
I'd go with the AC filaments on the Orcas -- you should hear nothing like hum from that pairing.
In fact, I'll test it out for you here as soon as I have a preamp as I just unboxed my SR-45s this morning.
-- Jim
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I'd be interested in your thought on how it sounds
Deb
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I just measured mine, I have less than 2mv at the outputs with the input shorted. How much less, is hard to say. I didn
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I didn't know that was the amps we were listening to. Very nice sounding amps
Deb
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To measure small levels of hum, I twist the meter leads together - it minimizes pickup of magnetic fields, typically from the power transformer but they are everywhere in a modern house. Ideally you would use coax.
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I would love the boards for this project if they are available. I do not need any additional instructions.
Michael
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To measure small levels of hum, I twist the meter leads together - it minimizes pickup of magnetic fields, typically from the power transformer but they are everywhere in a modern house. Ideally you would use coax.
We've been doing some empirical research in the lab with cables that past few days. The improvement in magnetic field rejection of coax vs. twisted pair is pretty amazing. We've been plugging various interconnect cables into a S.E.X. amp and listening thru headphones while moving the cable around very close to the power transformer. Some cable made with inexpensive Belden coax stomped everything else we tried for killing magnetically induced hum.
Before everyone runs out and changes over to cheapo Radio Shack coax interconnects (which worked great too), the downside is the coax we tried didn't sound as good as our hand made twisted pair in braided shield cables do. But I think it might be interesting to look into using coax for power supply wiring near a power transformer.
Perhaps the simple lesson from this is don't run your interconnects close to power transformers.
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Put me down for a pair of the PT2 transformers as well.
Do we have a count yet and how would we go about making this happen?
If we need somebody to coordinate a group buy, I'll be3 glad to do it, but I probably should wait until we are moved into the new plac ce -- say late August sometime.
Thanks,
Jim
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i'm in no hurry, but would like to get a set of boards and power transformers
Deb
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I actually want to build a pair of paramour IIs for 2a3s, so yes, would need an appropriate c4s/driver board for that amp as well.
This way I can leave the stereomour in the other system and not have to worry about moving it between systems.
-- Jim
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Ok, taking the bull by the horns, I've started an official PT2 group buy thread here:
http://www.bottlehead.com/smf/index.php/topic,3069.0.html
Please read the rules before posting there and I will update that thread as information becomes available.
Thanks,
Jim
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Quick question -- is the parafeed cap 3.3 or 10 uF for the SR-45 configuration?
Thanks,
Jim
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In the schematic that I have it is 10uf
Debra
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Quick question -- is the parafeed cap 3.3 or 10 uF for the SR-45 configuration?
Thanks,
Jim
I've posted a few times on this, but it bears repeating as a reminder, and in case someone comes across this thread "out of context". The value is a range, in this case 4.5 to 18uF; I chose 10 as about the geometric mean and widely available. Experiment! You will be glad you did!
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Does the Parafeed cap react with the speaker impedance curve? Or is it a match with the plate choke and/or the output transformer impedance?
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Thanks much Debra and Paul.
Grainger, the answer is "yes", but Paul has stated many times that one should experiment with parafeed caps in order to find the best match for your speaker load.
-- Jim
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Does the Parafeed cap react with the speaker impedance curve? Or is it a match with the plate choke and/or the output transformer impedance?
I'll take the opportunity toexpand on this a little, since it's a problem that I've struggled with for a long time.
I did a large amount of modelling with SPICE, some years ago. One conclusion was that EVERYTHING has an effect, including all the power supply capacitors, resistors, and chokes and the cathode bypass cap. Another conclusion was that you must include things like the choke DC resistance. Some effects are stronger than others, of course, but the minor players are not so minor that they can be safely ignored.
A further complication is that the output transformer inductance and equivalent series and shunt resistances are fairly strong functions of frequency and signal magnitude. And of course you must allow for a wide range of speaker impedances, which for a ported box will have two large peaks, one on each side of the low-frequency cutoff.
Given those difficulties, I conclude that it is impractical to use detailed modelling to choose the parafeed cap value. I then simplified the study to a resistive speaker load, perfect power supply, grounded cathode, and infinite inductance output transformer - in other words, just the plate choke, parafeed cap, load resistance, and tube plate resistance. This study showed that there was a broad range of capacitances that gave good results, and there is no value that produces seriously bad resonances. It's this range that I quote as suitable, and within which I suggest experimenting.
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I am using 6.8uf, with great success...John
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Now that we have the PT2 transformer group buy, is it possible to get the boards for the SR45.
I may be mistaken but from the schematic in the SR45 upgrade manual, the board looks like it is the same board from the extended FPIII. Of course the component values are different.
Debra
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What Deb said...
Also, seriously considering changing my driver/shunt reg tube to the venerable 6dn7 -- wiill the soft-start board still work for this application as well as a pair of paramour IIs?
-- Jim
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Now that we have the PT2 transformer group buy, is it possible to get the boards for the SR45.
I may be mistaken but from the schematic in the SR45 upgrade manual, the board looks like it is the same board from the extended FPIII. Of course the component values are different.
Debra
Hey Deb - remind me next week - I'm out of town again all this week and my notebooks are at home. The original SR45 board preceeded the current "soft-start" board, and it would be expensive to make just a few - plus the newest version (4.4) is better in several ways. I'll just have to make sure what the wiring changes might be.
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Paul
Thanks, will do
enjoy your time out of town
Deb
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Didn't PB come up with with a dedicated shunt board, a few years ago? maybe ha still has the file.
There were a couple of errors in the original instructions/ schematic, I will dig thru my notes...John
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I think this is it, from the old fourm...John
http://db.audioasylum.com/mhtml/m.html?forum=bottlehead&n=138093&highlight=sr45&r=&search_url=%2Fcgi%2Fsearch.mpl%3F
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By the way, I think the Dowdy Plate chokes would be a good fit for this amp (sr45). 125H and 40ma sounds like a good thing to me. Of course they cost about 2.5 times as much as the BCP-15. You might have to adjust for the dcr of the unit which is probably different (it is not listed on Mike's website). Probably would not change things by more than a few volts though. Then get the nickel outputs and you would really have something.
Michael
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By the way, I think the Dowdy Plate chokes would be a good fit for this amp (sr45). . . .
Well, they are not pretty, but I wouldn't call them dowdy. (I know Jim) Mike will still probably build them for this group. And I think nickel was awesome on Paully's Paramounts with 45 output tubes!
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I'm indeed building my pair with Dowdy chokes in M3 (courtesy of Keto) and TL404 autoformers.
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Regarding the Dowdy chokes, I have to ask exactly what will this buy you? I'm not challenging you as I'm sure you know far more about these things than I do, but I thought I remembered PJ stating more than once that there is a optimum ratio of inductance between the plate choke and OPT, and that because of the gapless nature of the pf OPTs, their inductance was so much larger than the plate choke, that it really wasn't of much concern to maximize the inductance of the plate choke. Of course I could be totally imagining this, in which case I apologize, but I'm trying to learn here and without thinning my wallet too much.
-- Jim
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BTW, I'm lurking on this thread because some of the best sounding amps I have ever heard are 45 output tubed amps. I'm hoping my last generation Paramour (1) amps might be useful for such an amplifier.
Paully's 45/MQ all Ni Paramounts were awfully sweet sounding.
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Jim,
It's my understanding that the more inductance you have (quality inductance) the better. Both VoltSecond and Mikey did some research in this area and it's posted on the MQ site (http://www.magnequest.com/tech_article2_voltsecond.htm, http://www.magnequest.com/tech2.htm) The Dowdy was designed for the 45 tube and still maintains a fairly low DCR. If there is room on the chassis I intend to use the Dowdy in my build also.
Aaron
(edited for accuracy ;)
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Hi Jim,
The rule of thumb I remember gives minimum inductance. In any case I'm using the Dowdys because I already have them.
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IIRC, the Dowdy choke is quite large and unlikely to fit on the Paramour II chassis.
To clarify, increasing the already high) OPT inductance has little effect. Bigger is always better for the plate choke.
Note that you would probably want a larger parafeed cap; I get 28uF (14 to 56uF range).
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Just to keep the discussion flowing, I also have a tl-404 looking for a home. I have been wanting to mate it with a 71-a tube with battery powered filaments(as the tube was originally designed for). I bet this sr-45 circuit would be killer for this application. It might even be possible to do shunt regulation and ccs on the power tube with the more modest voltage and current requirements of the 71-a. What does everybody think? Crazy?
Michael
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I've always thought about doing a SR 71A with TL404s. In my case I'd use the extra voltage to do a direct coupled one.
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With 380-400v available, I see no reason you couldn't do a shunt regulated, C4S loaded, direct coupled 71A amp. You'd want to trim the driver bias to get the voltages right, and re-adjust every so often - but if a half watt is enough for you and you're comfortable with battery filaments then you're already crazy enough that this will be no bother! What do you see for a driver? 01A perhaps?
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01A looks good. Battery heated filaments too at 5v and 0.25 mA (same as the 71A actually).
Paul, I think PGP 8.1s would be a tad better here than the PT-2s right?
I'm ready to go for it.
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01A looks good. Battery heated filaments too at 5v and 0.25 mA (same as the 71A actually).
Paul, I think PGP 8.1s would be a tad better here than the PT-2s right?
I'm ready to go for it.
PT-2 has more magnetic headroom, but the voltages etc. are significantly different. I'd need at least a conceptual design and voltage budget to comment further.
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I'm ready to build one too. Lets go for it.
Michael
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Now that we have the PT2 transformer group buy, is it possible to get the boards for the SR45.
I may be mistaken but from the schematic in the SR45 upgrade manual, the board looks like it is the same board from the extended FPIII. Of course the component values are different.
Debra
Hey Deb - remind me next week - I'm out of town again all this week and my notebooks are at home. The original SR45 board preceeded the current "soft-start" board, and it would be expensive to make just a few - plus the newest version (4.4) is better in several ways. I'll just have to make sure what the wiring changes might be.
Paul
Just reminding you about boards for the SR45
Hope you had a good trip
Deb
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Thanks, Deb - I had a great trip.
I can't seem to locate the SR45 conversion page - does anyone have the link at hand?
Meanwhile I'll mark up my schematic to show terminal labels and parts as used on the current (v4.4) board. I assume the original web page had a schematic? Hopefully that will be enough information to revive the design. The new boards are available as the "soft-start" kit for Paramount, including a trimpot for setting the driver bias precisely; you get a new driver socket (useful) and a 5670 tube (less useful).
It appears that the clip-on heat sink will work as long as your power line voltage is not much above 120v. This was always a marginal aspect of the original SR45 design.
By the way, the original used the 6CM7. The 6CS7 is very similar, but looks a bit more linear in the published curves. IIRC the pinout is a bit different, but just mention it in case someone wants to experiment.
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The instructions and schematic were never published but were supplied with the original kit instead. I have my own copy that could send to you Paul or to anyone BH authorizes me to do so.
Saludos
ps. Paul: I have a Board Meeting and Quarterly Earnings release coming next week so I really shouldn't be thinking about the 71As project. BUT so far what I have in mind is 01Aa driving 71As. Battery heated filaments. Independent PS for driver and power tubes with RS080 and exo-01 on the 01A and pgp 8.1s and (maybe Dowdys) on the 71A tube's one. DC, SR and C4S loaded each. I triamp but for this iteration I will only build two pairs because I wan't to try to direct couple the Ionovac tweeters (another project). I already have the two pair of TL404s, and most of the ps iron for both sets. I'll try to post a first attempt of a schematic next week. You mentioned "crazy enough", right? Let's set a new world record for Dunken factor.
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SR45 upgrade manual
http://www.bottlehead.com/et/adobespc/paramourII/SR45%20upgrade%20manual.pdf
Deb
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Good!
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Thanks, Deb. Turns out, I had downloaded it a while back but failed to file it where I could find it! That manual has the schematic which I propose to modify. (Actually it is a later version than what I have in my files - I'll check but I think I just added the RC stability network to the shunt reg part.) Notice that it's version 3.5 - there was actually quite a lot of development before the kit was offered!
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I made up a few sets of custom boards for this circuit a while back. They mount just above the power transformer, hold a large heatsink, and free up lots of space around the heatsinks.
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fimg526.imageshack.us%2Fimg526%2F9276%2Fdsc0193ij.jpg&hash=ca2cbf76e89c56adf8fbdd883792f27f817a6dc1)
I don't have a ton of documentation on these, but the connections are not too complicated.
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That is the one I was thinking of. I have always been a little worried about the small heat sink on mine. This also looks easier to implement then the original PCB. Granted it was not the original purpose but it is a bit of a Kluge with all the jumpers.
Would you consider having a few more made, or make the file available?...John
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I will talk to Doc/PJ on Monday about this. Last time I made a few, he and PJ gave me their blessings, I'd just want to double check that this is still OK.
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Xavier,
If you are using two power supplies you might have enough voltage headroom to have c4s loads on the shunt regulators and on the plates of both tubes. Of course this would cut down on the Dunkel factor.
Michael
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I guess I have to say this, lest the thread get out of hand.
I have NOT placed this design, or the circuit diagram, in the public domain. When it was a semi-kit, I got some recompense from the sales. And, as I said early in this thread, I am working on a second-generation version from which I expect to get some income if it does become a kit.
I don't have a problem with a few enthusiastic Bottleheads making versions for themselves, especially if it involves purchase of PT-2s and/or C4S boards, both of which produce some income for me. It does become a problem for me if I lose ownership of the design. It's more a legal issue than a financial one - my monetary compensation is small, but it does validate ownership of the design.
Intellectual property is a very tough issue, which we as a society are barely starting to deal with in an age where copying and disseminating have become so much easier. I'm sure the whole concept will see huge changes over the next couple centuries. Meanwhile we muddle through as best we can.
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Hear hear!
And good to know a revision could end up in a kit. I'll do a pair (already ordered the pt-2) to see what the buzz is about with my 755As. And if you guys eventually come out with a full kit count me on!
Saludos
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I also have purchased the A pair of PT-2's, and would be happy to buy the revised kit if it becomes avaiable.
I hope I did nothing wrong by posting the link to the manual earlier. I was just posting a link to a post that was already available on this forum.
Deb
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Deb, Xavier, in fact the posters on this thread, you are all A-OK in my book. The link issue has been a grey area, it's not linked from the site but not protected either. So far it hasn't been a problem. I'll consult with Doc B on future plans, perhaps the revised circuit on request with a transformer or C4S. I really didn't want to bring it up but I also don't want the circuit to show up on non-Bottlehead forums.
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I totally understand, and would never consider discussing the circuit outside of the bottlehead forum.
Deb
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For the record, I bought the original kit. Just looking to tweak and improve...John
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Paul,
I have total respect for your design abilities and expertise. I have gotten a priceless education following the discussions on this forum over the years. I think Bottlehead products are extremely high quality and reasonably priced. The last thing I want to do is step on anybody's toes.
So I want to make sure it's cool if I purchase the soft start boards and use them to build a 71-a amp.
Michael
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Paul,
I have total respect for your design abilities and expertise. I have gotten a priceless education following the discussions on this forum over the years. I think Bottlehead products are extremely high quality and reasonably priced. The last thing I want to do is step on anybody's toes.
So I want to make sure it's cool if I purchase the soft start boards and use them to build a 71-a amp.
Michael
No problem there!
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I have the odious position of making decisions about this stuff, and for now I have removed the PDF until we determine how to proceed.
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OK pals. We have to keep this thread moving even if its only those of us who paid for the original kit and, in consequence, have access to the schematic (just like any other BH product).
I have two comments/questions: First, one of the things that originally discouraged me of using my TL404s in this project was that the OPs were optimized for a 3k load. Having said that I think that there's voltage headroom to increase the regulated voltage a little bit to 350 volts and then operate the 45 at "classic" 275/-56/36mA conditions. Moreover this would reduce the power dissipation needs of the heat sink. I realize there may not be enough B+ at low mains voltage conditions but in my case: A) I have a perennial ultrahigh mains voltage and b) I use power plant conditioner so I always have 119v at my BH gear ;)
Second, why can't one just substitute the plate choke with a C4S as Michael was suggesting? a 36mA C4S with a 20v voltage drop would only be dissipating a quarter of a watt.
Saludos
Saludos
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Paul can answer this much better than I can, but no it doesn
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Hi John,
Actually I'm not proposing to increase the current, the classic op and the SR45 one share the 36mA current.
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Xavier, a plate load dropping 20v would allow about 10vRMS swing, allowing 6v minimum compliance. That's about 0.020 watts in a 5K load ... That said, I do have some plans for a C4S loaded 45 using the Paramount power transformer; the problem is finding a reliable current source device at such high voltages. It's on my list. :^)
You can drop the plate current for a 5K load; I'd go with 30mA at 250-275v. It leaves more current for the shunt reg which is a little starved due to the PT-2 limitations. (That's another reason I want to switch to the PT-7 eventually.)
For those who bought PT-2s with the intention of resurrecting this 5-yr-old design, I'll see if we can send a paper copy of the original notes. For those who want a replacement for the original C4S board, which is no longer available, I recommend the Paramount soft-start kit and I'll throw in a paper copy of the modified circuit diagram showing the connections to that board. That should bring the project to about the level it was originally - it was never a real kit with a real manual, after all!
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Will the Paramount soft start boards be an upgrade from the original boards?
I was able to get an original unbuilt SR45 upgrade kit from 2007
Deb
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For this application, the difference with the new boards is insignificant. The differences are 1) a different heat sink (I believe the capacitor is about the same), and 2) there is a trimmer to adjust the driver bias; the older board just has a resistor (the driver is cap-coupled so there is no special need to trim the voltages exactly)
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Oh good -- that saves me a bit of money then.
Somewhat related -- would you recommend the paramount 1.1 softstart boards and 5670 driver for use in the paramour IIs I also want to scratch build?
Thanks,
Jim
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@Jim, yes I would recommend the paramount 1.1 softstart boards and 5670 driver for use in the paramour II. There are no instructions specific to the Paramour, since it's been out of production for a while now, but it should not be that difficult to figure it out.
I also mention that, because the driver bias is adjustable, you can probably use other tubes such as 12AU7 or 6SN7 if you need less gain.
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Paul,
Great! And maybe also the 6j5 too. Now if I could just come up with some nickel TFA 2004s I should be well on the way to a really nice pair of 2a3 monos to be swapped with the SR-45s in my main system as mood and music dictate.
-- Jim
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TWO 6J5s, that would be ... shunt reg, you know... :^)
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Oh, indeed -- forgot about that extra bit of goodness over the stock P2s. I recall how much I liked them in more or less stock form and I can only imagine how nice this pair will be.
-- Jim
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"Xavier, a plate load dropping 20v would allow about 10vRMS swing, allowing 6v minimum compliance. That's about 0.020 watts in a 5K load"
Thanks Paul. It looks like I still have lots to learn!
You can drop the plate current for a 5K load; I'd go with 30mA at 250-275v. It leaves more current for the shunt reg which is a little starved due to the PT-2 limitations."
Fantastic. I assume the 250-275 is plate to cathode. Right? That's a bias of 50-55 so I need 300-330v at the plate, 315-345 on top of the plate choke. So the design Breg at 320 is fine.
To get a 50v bias the cathode resistor would be 1.66k.
Good for approximately 175mW and approx 6.8% THD.
Now, my big question: would I need to change anything at the C4Ss to account for the 6 mA less I'm running through the 45? Or does the shunt tube just shunts them?
Thanks a lot!
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The shunt tube does the work.
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Awesome!
Thanks Paul.
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Resurecting this discussion to run some ideas past the group.
I'm considering using my new PT2s to build a whole second SR-45 amp, but with a few changes...
First, I'm considering building both amps in one chassis -- like John did, and going with a slightly larger plate -- maybe something like 12" x 18", all film cap psu, and also looking into the possibility of using separate filament transformers and the FC1 to supply the 45 filaments. Aside from the obvious reason, I'm also thinking this will take a bit of the load off the PT2 so I can run a 6dn7 slightly more comfortably.
I have a pair of Dowdys on order with Mike, and those come with endbells so I'll most likely mount them above the TFA2004 jrs, which should free up a slot for placing the fc1 in a magnetic null formerly occupied by the plate choke. Also, the orientation will be rotated so that the opt and plate choke are at the rear of each half of the amp, the 6dn7s near the back and the 45s up front and keeping the pt more or less in the center of each side of the amp.
So, I guess what I'm asking is if my thinking on the lightnening of the pt's load for the 6dn7 makes any sense, and two if a separate filament tx and the fc1 have any issues associated with them -- so sort of like a hybrid sr-45 and paramount, and using the paramount driver/shunt reg board with the 6dn7.
This will allow me to leave the current sr-45s pretty much as-is and only steal the tfa-2004s when the time comes.
Thoughts?
-- Jim
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One of the unique features of the PT-2 is that the two halves of the 6.3v winding surround the 2.5v winding, shielding it from line noise and rectifier spikes of the high voltage and primary windings. If you use another source of filament power, you might want to try it both ways to see if you hear a difference - I never did that experiment, just designed in the shielding from the first.
The PT-2 runs at 10-11kGauss, much lower than the usual transformers (16kG; 13.5 for 50Hz rated but operated at 60Hz). This reduces vibration as well as radiated magnetic field. Consider getting transformers with dual primaries so you can wire for 240v, run at 120 - if you want to preserve this advantage. Be aware that split-bobbin transformers, which are very common these days, do have large external electrical fields unless you have a grounded shell or end bells. The split bobbin does reduce capacitive coupling between primary and secondary, providing a similar benefit to a shielded winding at a lower cost.
The PT-2 will run a bit cooler with a lighter load, about 10% less than a standard Paramour II.
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Hi Paul,
thanks much. I'm not sure I completely follow the part about 240 v primaries, but that's probably due to my lack of transformer winding schedule knowledge.
I also wondered if I may need to load the 2.5v secondary some to keep voltages from going too high -- or maybe that doesn't matter so much with the shunt regulation -- except for the 6.3v filament, but that can be adjusted other ways.
Still, most of this will depend on what I experience once the sr-45s are in the system -- which of course means the system has to get put together first. I'm working on it... :-)
-- Jim
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Question for PJ -- are any of the new shunt reg/c4s borads going to be useful in the SR-45? A related question would also be if there is any progress on a new driver board for the sr-45s, or would y9ou recommend that people use the paramount soft-start board?
Getting ready to start planning the new layout for the stretch model sr-45 -- 11-1/2 deep instead of 10" but still 8 wide, portrait orientation, and monoblocks is what I've settled on -- just works much better with the rest of my system to keep them as monoblocks.
Dowdys will go on top over the OPT, grid chokes will go where the plate chokes used to be, and the space between the driver and 45 will probably be mostly eaten up with a 27-33 uF PF cap (the downside of that huge 125H Dowdy.
I'm also going to go with AC filaments and most likely 6dn7 driver/shunt reg tubes.
Thanks,
Jim
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Jim-
Sorry I missed your Sept 4 post; the forum software is not perfect (!) To answer (sort of) - because all transformer secondary voltages depend on the primary voltage and to a lesser extent on the other voltages and currents, there is no answer beyond "try it and see what you get" for filament voltages. Resistive losses in the wire from transformer to 45 filament are not going to be zero, as well! Best bet is to make a "true rms" measurement if you can, or can borrow a suitable meter; line voltage is far from a pure sine wave and the rectified high voltage makes the other windings even worse. Plan on possibly slipping in a suitable resistor...
As for the C4S boards, the latest version (v.4.4) is still what's in the Paramount "soft-start" kit. It has an adjustable bias trimpot for the driver section. As I think I've said before, this board does not have a really heavy duty heat sink for the C4S feeding the shunt reg; if you line voltage is over 120v that can be a problem. It's one I still plan to address in a new design, but that has not progressed in the last few months - the BeePre has taken most of our time lately.
I hope this is helpful; I've kind of lost track of this thread and don't remember all the things going on....
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Hi Paul,
Yes, I too have lost track of all the details -- and yes you did say that the SS board in the paramount is not really up to the job -- I just forgot about that.
I haven't measured the line voltage in the new place yet, so will do that tomorrow.
Now I'll have to look at what the range of options are for that monster pf cap :-)
Do let us know when you're ready to look into a new driver board though.
Thanks,
Jim
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I must be lost in this post. PJ, were you going to redesign the board or stick with the design from the old board? If there is no planned change on the board, could we put together a small group by on a run of boards?
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PJ/PB,
It seems I missed out on the PT-2 order. I intend to use different heater transformers. Would the PT-7 be the next best transformer to build around?
Thanks,
Aaron
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I will have a new design - it may incorporate some of the Crack Speedball and/or BeePre boards, not decided yet. The old board has some issues I am not at all happy with.
It will be based on the PT-7 and include DC filament power. The circuit is pretty close to done, but the parts and boards are not selected yet. Right now the BeePre is still taking up a lot of time, getting all the parts in-house and tweaking the layout for the manual.
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Thanks Paul, I'll take a chill pill and await the new design :D
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Paul,
So, will any of these new boards work in the old sr-45? I already know the answer regarding the soft-start board :-), but interested in backwards compatibility to the existing design. In the case that that won't work, can I transplant all the nice iron (nickel tfa-2004 jr, dowdys, and bpc-16ni to the new design? I'm assuming you're designing for the s.e.x./stereomour output transformers and of course I'm wondering if there is enouugh wiggle room in the operating points to work with the 3k of the TFA-2004.
Best for me, of course would be to be able to use one of the new driver boards in the old existing design.
-- Jim
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Jim-
I had to spend several hours on ferries today, and used the time to look at alternatives.
Right now, what appeals to me the most is a completely fresh design. It always bothered me that we made so many compromises to get away with existing parts and layouts, in what was (IMHO) our best-sounding amp - the topology was way ahead of the rest of the design (AC heater, no time delay, etc.) I kind of hate to do this, I always liked the idea of growth paths, but the original WAS a growth path, compromised to work with the original Paramour II, and it just didn't sell enough to make economic sense.
The original was an experiment; only a few were made and the manual was nearly non-existent. I learned quite a bit from that experiment; among other things I learned that this is never going to be a big seller. Even if I come up with a prototype that sounds great, I have doubts that Doc B will want to develop a full-scale manual in the traditional format - that's a LOT of work and has to be spread over many units to make sense. It may only makes economic sense as an already-built amp.
So I am thinking of a much larger circuit board to house the power supplies - including regulated DC on the filament and heater, as well as the shunt-regulated high-voltage power. The manual for PC boards should be simpler to do. I'd like to do it with all film caps (except for the heater power, there are no polypropylene caps at 10,000uF!), and include time delay relays for high voltage and for shorting the OPT to prevent core magnetization. And impedance switches and an input level adjust for channel balance - the whole nine yards.
The MQ iron would still be a reasonable choice for the operating point, and the chassis plate may or may not be the same - that partly depends on whether or when we update the Paramount chassis. Of course, the Dowdy choke won't fit on any of our chassis plates anyhow ...
Of course, this is not set in stone yet. If there's an outcry for something more Bottlehead-y and less high-end, I have a few ideas. I'm just thinking that only a relatively few people will be into it so deep as to want a spendy 2-watt amp.
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Thanks PJ for the update. Hopefully others will chime in but I for one look forward to your 'high end' design. May they be the sweetest 2 watts available ;D
When you set the primary impedance will you please let us know?
Regards,
Aaron
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I'll use the SEX/Stereomour output iron at 4K primary, so the load impedance will be 2-4-8-16 ohms. That's been central to the plan all along. It has a generous magnetic headroom at this operating point, and most listeners - including myself - have been very happy with it. The Magnequest BH-5 at 3K is still suitable, as is the BH-2 plate choke, and I'll try to leave room and mounting holes for them.
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Paul,
Thanks for the detailed reply and explanations. I think, given what I have and have invested in, it makes most sense for me to just continue on the path I'm on, perhaps design and build a more substantial heatsink for the existing driver arrangement/shunt reg board, and my larger chassis.
I will however possibly look into the opt shorting switch/relay, but realizing that would require an additional power supply that may or may not impact noise levels. Also, given my speakers' sensitivity and the existing reports on the amps noise performance, I'm not sure how much, in reality, I'd gain in sonics over a fully maxxed out version of the existing design -- vcaps, copper chassis plate, dowdy, foam FEP OCC wire, etc.
After all, it's still going to be 2 glorious watts! :-)
-- Jim
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I have three pairs of TL-404s waiting for this project to go forward (it took me many years to get a hold of them three).
In the meantime I'll build a First Gen SR45 with the PT-2s, Dowdys and Cobalt pinstripe 2004 Jrs. For the WE's, that is.
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Xavier,
I want those cobalt tfa-2004 jrs! :-) I wish there could be another run of the cobalt iron from MQ. Not that the iron I have on hand and on order is anything to sneeze at, and will probably be the best amps I've ever owned, but still... :-)
-- Jim
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Xavier,
I want those cobalt tfa-2004 jrs! :-) I wish there could be another run of the cobalt iron from MQ. Not that the iron I have on hand and on order is anything to sneeze at, and will probably be the best amps I've ever owned, but still... :-)
-- Jim
I have first dibs Jim! Sorry my friend ;D
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Hmmm, maybe I should start an auction?
Sorry pals. You're gonna have to come down to Mx to listen to them!
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So is the general opinion that the old SR-45 should be shelved in favor of the the upcoming boards? I happen to have the orginal kit and a couple of PT-2 transformers that I was going to try to make music with soon. Will there be a significant improvement from the old amp to the new? Are the newly proposed boards ready for production or behind other more profitable kits (just trying to see how far down the "to-do" list these are for Paul)?
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Xavier,
Ok, and I'll bring the Hacienda de Chihuahua :-)
Alonzo, I've thought about this too, but at least for now I'm going to stick with what I have as I believe it will be a fine amp and I'm just not sure I will really need the DC filament supply. A great amp is still a great amp :-) Of course this is just my approach and for now, but I'll keep an open mind for the future if it turns out to be a significant enough upgrade.
-- Jim
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The new design has two main features - DC filament power for lower hum, and a bigger heat sink for better reliability. It may have film caps for reliability as well; that depends on where Doc B wants to position it, which depends on who we expect to be the customers. If the hum is no problem (it seems to run around 1mV with good 45s, which is actually quite low for an SET) then there would not be a great deal of sonic difference.
The other difference is the OT-2/PC-3 output transformer and choke, which is better matched to the 45 than the original Magnequest iron. I'm not saying my design is better than Mike's (!), just that a 4K load gives better damping than a 3K load.
As for timing, we recently had a great brainstorming session to look at new product development for the next year or two. We haven't documented the results or made all the decisions yet, but we do have a general idea of where we want to go. I can't be very specific yet, but now that the BeePre design is pretty much finalized, the DAC is the next priority. My involvement is just the analog tube output and power supply and won't be so all-consuming, so I'll probably work on the SR amp at the same time.
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Thanks Paul. Sounds great. That time frame will allow me to save some money for my three pairs (did I mention I already have three pairs of TL404s waiting for this to happen?). I like the 4k better than the 3k because it's closer to the 5k of my 404s. I know you like 404s.
Jim: We're ready to have you here. No need to bring the tequila. I have some :)
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I am keeping my fingers crossed for the film cap PS. Would it be too much extra to design two different PS boards, one for film (with a choke or two) and a standard CRC supply to cover both bases? Or possibly making the film supply schematic an option and we could point to point a PS for it in a none standard chassis? The film supply board would find nice cross coverage as an upgrade path for the Paramounts too.
Just brain storming here is all ;D. It seems in the classic BH spirit people intend to customize the design regardless. Mine will put a pair of Dowdy's to use and an oddball OPT for Stax headphones. Thanks PJ for keeping this project alive!
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Would it be too much extra to design two different PS boards, one for film (with a choke or two) and a standard CRC supply to cover both bases?
Two power supply boards for an amp that isn't likely to be a big seller is unlikely. On the other hand, I think Doc, PJ, and I are all desiring to get as many of the electrolytics out as possible.
-PB
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1
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On the other hand, I think Doc, PJ, and I are all desiring to get as many of the electrolytics out as possible.
-PB
;D
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We also have some other experiments to do that could set this apart from the original SR-45. That circuit is quite exceptional as-is, but we have to do our due diligence before release to ensure that we haven't "missed" any opportunities.
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You can experiment all you want as long as your end design works with my 404s. :)
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Not to worry, Xavier, I have already analyzed a different set of resistors to best match a 5K load. :^)
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Not to worry, Xavier, I have already analyzed a different set of resistors to best match a 5K load. :^)
:) :) :)
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Thanks
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PJ, if you could factor in an available 2.5v/4% tolerance/1.5 amps supply for the heaters so that we can safely use EML tubes, I would appreciate it! ;D
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Would the Magnequest sex amp upgrade iron be suitable for this project?
Michael
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I use the sex mq plate chokes with tfa 2004 jr outputs (currently m4/co slice). I cant recommend the current amp enough. I just put in a pair of cobalt grid chokes and im listening to it after and the bass is slamming. I am trying to think if i turned up the sub levels. So yesterday n all day im just amazed at the bass. Im thinking the sub is really sounding great. So 2 days later i noticed i had disconnected the sub from the amps when i worked on them and not reconnected them. Amazing bass now! And i always thought it was amazing bass...
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PJ, if you could factor in an available 2.5v/4% tolerance/1.5 amps supply for the heaters so that we can safely use EML tubes, I would appreciate it! ;D
2.5v at 1.5A IS the 45 tube spec, so it will certainly handle that ...
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Terran,
Amazing bass? How sweet the sound? Sorry, couldn't help myself.
BTW, are those the Orcas you're talking about?
That would be the second time I've heard about people marvelling at the bass and then realizing they didn't have the subs connected/turned on.
-- Jim
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Lol nice lyrics! it was actually the Abbys. Can't afford the orca subs yet. I have been ok with the abbys always wanting a bit more but this mod has transformed the speaker. The orcas are on my desk at work with my pdg and doing very well...
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So Clark says you two (PJ, PB) got a chance to listen to his new Feastrex cab design ;D
I'm now in for two pair, one for headphone use and the other to drive this upcoming speaker.
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Pj,
Another quick regulator technical question: Since the Ddowdy is more than 3 times the inductance of the bpc-15 that's in the amps now, will that appreciably lessen the load on the regulator?
And count me in as wanting to hear any impressions on the feastrex speakers under development by Clark and Molly. If I can afford it, this would be the only speaker I'd really consider upgrading to at some point in the future.
-- Jim
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Yes, a larger choke will reduce the fluctuation in the regulator current at any given frequency, or perhaps you can say it will have the same fluctuation at a lower frequency.
As to the Feastrex speakers, it's way too early to say anything beyond "they seem promising." We heard them in some cabinet that was on hand, not at all intended for these drivers, and they had (I think) less than 10 hours on them.
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Paul,
Thanks for confirming the larger choke concept.
As for the speakers, sorry, I thought these were the new cabinets and Clark's well-seasoned drivers. Yes, can't tell much given what the configuration was. Guess we'll just have to wait for Clark to get some prototype cabs done.
-- Jim
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Jim and Aaron:
http://www.ebay.com/itm/Pair-Magnequest-TFA-2004-Jr-Cobalt-Transformers-Pinstripe-version-M4-/261140242206?pt=Vintage_Electronics_R2&hash=item3ccd2bdf1e
The price is stupid (I guess) but maybe sending the guy an offer?
And another maybe even sweeter?
http://www.ebay.com/itm/Pair-Magnequest-EXO-36-Cobalt-Transformers-/261140247083?pt=Vintage_Electronics_R2&hash=item3ccd2bf22b
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Paul,
I'm thinking of using a huge pair of BAC100 chokes (in my stash already) for the PS instead of the good ol' triads. I don't have the DCR handy but the BAC80s is 325 ohms so assuming this one is not far away it wouldn't deviate much from the 270 of the triad. Any concerns?
Thanks
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Xavier,
Thanks for thinking of me but I won't have that kind of cash until we sell our other house, besides, even if I had the money, not sure I'd pay that much for these. Wonder what they sold for originally, or what they'd cost new today?
-- Jim
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I don't expect them to sell for that much. But you never know!
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Aaron, you should pick up those EXO-36s -- if you use the 16 ohm tap they will have 5k equivalent primaries. A cool 3 grand for a couple of transformers you can drop in your shirt pocket :-).
-- Jim
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That's just crazy talk Jim! I know where a pair of full blue 2004 jr's are hiding if your heart is set on a pair but they would still be expensive. I'm considering silver wire with M3 depending on the price ;)
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I was told the full cobalt tfa 2004 jr went for 1$k. The m4/co stripe jr's $800. I much prefer the m4/co stripe to the full cobalts. You get better bass from m4 and take advantage of cobalts crisp airy highs. I would go for those before the 36's plus theyre cheaper. But honestly full nickel is very similar to my ears. Fwiw. Taran
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My 2A3 stereo power amp uses the MQ TFA 2004 Jr's with M4, and ten slices of cobalt in the middle of the coil. They are 'the Bomb' in my opinion. I think I got my pair for $600 back when Mike released stats for them noting 80% of the inductance of the full cobalt stack. I can testify(now that I have the Orcas and a pair of BUF subs) that they really extend the bass and highs are clean. You can see the cobalt slices in the middle of the coil in this pic:
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I measured the BAC 100s dcr at 250 ohms so they are drop-in vs the triads. These are going to be heavy amps.
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is there a difference between the magnequest TFA 2004 and the TFA 2004jr??-and how about the EXO 45-i am ready to purchase some output transformers for the SR45 along with the plate chokes which the bcp-15 is called for --there has been discussion of the dowdy chokes!!! looking for some input--thanks howie
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Hi Howie,
The difference between the tfa-2004 and the junior is the size of the lamination stack -- and thus the poer handling. For a 45 or 2a3, the jr is plenty robust enough and *may* have a slight advantage for a lower power amp as it will have less core losses.
The EXO-45 is a 5k primary (instead of 3K fpr te 2004s) and I believe has a maximum power handling capability of 3 watts -- still enough for the 45 but may be pushing it with a 2a3, but it's not a typical primary impedance for a 2a3.
For th bpc-15 you want the 50 henry, 40 ma flavor for the sr-45, or as you mentioned, the Dowdy. Downside to the dowdy is that it may not fit on an existing chassis (it mounts on top and has endbells), and with a 3k primary impedance on the tfa-2004/jr, the parafeed cap will have to be fairly large -- midpoint is about 28 uF -- and at 630volts, that's a biggie!
Hope this helps,
Jim
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hi jim -thanks for responding-i think the dowdy choke would be out-not due to its size as this will be my first scratch build and the chassis will be custom- 28uf now thats a lot of cap-a little pun eh!!!!--magnequest does not show the 2004 jr- so the 2004 or the exo 45 would be the options -is there a advantage to having the 5k over the 3k impedancel-howie
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Jim,
The obbligato's praised by Grainger come in such high values and are not expensive. Those will be my in mine I think. For the coupling caps I'll use vcaps.
Do you think it would make sense to group and buy together the basic components. That is, the psu and ps ones. Anyone else?
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The BH-5 replaced the TFA-2004Jr as tha Paramour upgrade. The accompanying BH-6 choke (40H/50mA) can be used, or you can ask for a BH-2 which is the same thing but gapped for 50H/40mA.
The original circuit was optimized for 3K impedance. The one I am currently working on is optimized for 4K. Performance is fairly insensitive to impedance - if I had to chose a range I'd say 2/3 to 3/2 of the design target is OK.
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Howie, I think there was at least one person who built his sr-45 with the eo-45, and there was probably some discussion on this in another thread. You would get a slightly higher damping factor with the exo-45, but how significant that would be in audible terms I have no idea.
Xavier, I already have everything as I found a bunch of mundorf m-tube caps when going through all my piles of stuff, and I may even use a couple of the 30 uF ones for the PF cap. Thanks for the reminder of the obligato -- I'll have to go have a look at those too. And I also found the Continental caps come in a 30uF 630 v size that isn't too huge and not horribly expensive, and gets some nice comments (it is of similar type to the v-cap OIMP -- oil filled polyester), so those may be worth checking out. I also already have the .1 uF copper/teflon v-caps. I think there is a reality MR series in this value too, but it may be just too huge, and the price tag is more than I'd want to spend. The larger value v-cap OIMPs don't have sufficient voltage ratings and of course they are way pricey too.
Paul, unless you know otherwise, Mike does not seem willing to sell BH upgrade iron a la carte -- everytime I've asked, it's the whole package or nothing at all.
-- Jim
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Xavier,
Are you talking about the old version or upcomming version? If the later, I'm in for a group buy. I imagine we could save some on PS caps, relays and such. You are building three pair correct? I'm in for two pair.
Aaron
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I was talking about the old one but I'll do three pairs of the new one so ... unleash hell.
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Well, if Mike won't break up the set you will have to wait until he does another run of TFA-2004Jrs.
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Or buy the set an give the chokes another use.
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The pair of Jr Co that the seller was asking 4k for are now an auction starting at 399. Just a heads up!
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Thanks Xavier.
Things should start to move forward now that the BeePre is on street :) :) :)
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Thanks Xavier, but I now have my plan in place and I certainly don't have the momey to get into an auction at this point as nice as the Co Jrs would be.
Today there will be a box arriving from a a guy in Philly with a couple of massive plate chokes in it, with more boxes to follow soon. This box will have a fresh pair of Dowdy chokes gapped for 60 mA in it, and which may just find their way into my planned Paramount 2a3 build.
Tomorrow another box from BH will be arriving -- this one with the last of the FP IIs, but with a few twists :-).
Plan to be up with the SR-45s driving the Nagas and subs this weekend.
-- Jim
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The pair of Jr Co that the seller was asking 4k for are now an auction starting at 399. Just a heads up!
Nobody is bidding on those...I'm not. ::)
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Did anyone here win the auction for the TFA-2004jr cobalt pinstripe on ebay.
I bid but was not fast enough at the end to win
Debra
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How much did they go for?
My pair arrived today!
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They went for $733. I fI had won them I was going to use them in a SR45
Deb
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Today is a great day!
My brother delivered from the US my new pair of 2004Jrs with Co pinstripes for a pair of "Mk I" SR45s to be used with the WEs. He also delivered the third pair of TL404s to build an equal number of SR45 "MK II" amps for the main system when the new design around PT-7s (maybe a new kit?) comes out.
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Just a ping for an anticipated project. We are awaiting it with baited breath PJ!
Half of my custom iron has arrived for this project already. In the mean time I've been enjoying a Firstwatt SIT 2 amp (impressive). I anticipate that the SR45 will trump in in sound but not in power.
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Thanks Aaron, I need the push. There's another project just ahead of it but I should get back to it shortly.
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Great Paul!
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Where might I pick up a schematic for the SR45?
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The SR45 was a one-time design, never a full kit, and is not currently supported. I am working on a replacement to resolve some of the issues with the first one. I discourage spreading the design around (beyond original purchasers) for several reasons, both technical and professional. For the latter, see post #58 in this thread.
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The SR45 was a one-time design, never a full kit, and is not currently supported. I am working on a replacement to resolve some of the issues with the first one. I discourage spreading the design around (beyond original purchasers) for several reasons, both technical and professional. For the latter, see post #58 in this thread.
I understand and respect that, Paul. I'll wait patiently until the replacement arrives. Please include me in the category of interested and considering purchase.
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Tom, YGPM...
Also, I tried the SR-45s with my preamp and the Orcas and while a tiny bit better than with the nagas in terms of max volume, the fact is that there simply is not enough gain in this system, so I'm afraid I'm going to have to give up on the SR-45s. I'm afraid it will have to be the 2a3 paramounts that will poewr my blumenstein Nagas -- not that's a bad thing, but I was looking forward to the SR-45s as my mainstay amp.
PJ, I assume the new design will not have any significantly higher gain?
Thanks,
Jim
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Just another vote for this project. The minute it's available I
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... PJ, I assume the new design will not have any significantly higher gain? ...
So far, it has been my plan to repeat the choice of driver tube, with a fairly low gain. However, I think we'll have to convene a brainstorming session and revisit the gain structure question in a more consistent fashion - our preamp gains are less than they were a few years ago.
For what it's worth, the SR45 needs a nominal 1.65v to generate full power. The BeePre has a gain of about 2.5, so an input of 0.65 volts should generate full power from the SR45. A redbook digital source with 2vFS should then be able to drive the SR45 into clipping by 10dB.
For comparison, Paramount 300B requires 1.56 volts but makes 8 watts instead of 1.5 watts. SEX and Stereomour take around half that, 0.75 volts for full power of 2 watts and 3.5 watts respectively.
However, some modern recordings may utilize more headroom than traditionally used, and some source devices deviate from the redbook output standard.
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Thanks, Paul. I'm a little baffled by what's happening with my sr-45s then as in theory at least, a unity gain preamp fed from a 2v nominal cdsource should get the amps pretty close to clipping, and with the Blumensteins, they just don't appear to be anywherre near that.
Tomorrow I'll try my 3 watt LM mini amp that is much more sensitive. Wish I had some good test equipment to test all this stuff and see what's going on with the waveforms.
BTW, for those who haven't seen it, I'm looking at selling my SR-45s:
http://www.bottlehead.com/smf/index.php/topic,3924.0.html
Thanks,
Jim
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This may one of those times when theory meets practices. I have the same experience as Jim. A "2V" source, without an additional line stage will not drive my SR-45 to full power but will drive any other amp I have (many), plenty loud. Now these amps are not only probably more sensitive but have more power. My system with Horn Shoppe Horns, needs all the power a 45 can deliver and with a line stage it is plenty.
I did briefly try to increase the gain of the SR-45 by subbing a 12AT7 for the driver, I only tried it at the 6CM7 operating point. I got a bit more gain but didn't like the sound as much as the 6CM7, what was a bit of a welcome surprise.
All in all, the SR-45 is my favorite amp, so if I need a line stage so be it...John
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The squeezebox 2 powers it up nicely for me but the ipad/phone are too low. I did get a big jump in volume from switching the coupling cap from a russian teflon to vcap.
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Teran,
YGPM/EM
-- Jim
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I did briefly try to increase the gain of the SR-45 by subbing a 12AT7 for the driver, I only tried it at the 6CM7 operating point. I got a bit more gain but didn't like the sound as much as the 6CM7, what was a bit of a welcome surprise.
A 12AT7 will burn up (somewhat quickly) if you rewire the socket for a 12AT7 and drop it in, as the shunt regulator section dissipates over 4 Watts, and the 12AT7 is rated for 2.5 Watts.
Also, with 8 Volts of bias and 36mA, your plate voltage will drop way, way low, and you'll run out of swing in one direction (along with raising the heat dissipated by the driver C4S).
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I'm going to take Teran's advice and try a new coupling cap. The amps do have KK teflons in them now, and I do have a pair of .1 uF vcap CuTF caps I can try. Tomorrow we're supposed to get a healthy dumping of snow, so we'll be mostly contained at home for the weekend, so it will give me something interesting to try. I don't feel I need all that much more volume, so this may just put me in the ballpark, if not for all listening, at least a good bit more of it, and then the 2a3 paramounts can be changed in for the heavy lifting. Funny to think of 3 watts as heavy lifting, but there you go :-).
I'll report back on this later in the weekend.
-- Jim
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The 12AT7 was used only for the driver, I kept the 6CM7 as the reg...John
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An update on my gain/volume situation...
Ok, first, this is really hard to admit, especially since I did the samething three times in a row when swapping speakers: I got an instant nearly 6 db gain simply by connecting the speakers in phase ;-). How I did that, especially with these speaker cables (which are so obviously different on positive and negative sides) is a complete mystery, but that alone made a nice difference. Another mistake I made wa to not play the amps or speakers long enough for them to wake up and for the nickel core demagnetization to happen. So all that together got me about another full 99 db or thereabouts, which is a full step on the coarse volume control.
I could not locate the vcap CuTFs, so I just put the cd player on repeat and let the system play while I finished organizing my toolbox and moved almost of the remaining junk out of my listeninr room and set the area rug in place, and sure enough after an hour or so things really started to come into focus, gain some far more substantial weight and far better top to bottom balance, clarity and tonality. I also have to remember that a substantial part of this system is brand new, including all but one set of interconnects and the CD player.
So, as things got better and better over the course of a few hours, it became pretty clear that I'm going to stick with these amps, but also probably keep the Orcas in the listening room. That will mean chopping the stand height down somewhat as they were sized for another room and a much higher couch. Oh, and all this was sans subs again. I'm still kicking myself how I could have connected the left speaker out of phase originally, and then two more times when switching in orcas and then back to nagas, and only caught it today when I put the Orcas back in -- I guess I was just on autopilot and did the same thing everytime and today as I was pluggin the cables in something clicked and I thought, this is not right.
Other than that and a somewhat flakey 6j5 on the left side of he preamp, all seems to be coming along nicely now, and I've got a NOS pair of RCA 6j5s in my mailbox right now which I'll go fetch tomorrow. Then if I can't find the cutf caps, I just got an unused, unwanted pair of .1 uF Mundorf SGOs for half price, so I may throw those in too.
Despite all this, the listening after the first couple of hours was really nice. Computer and dac and room treatments are next.
-- Jim
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A CL 90 at the mains input reduces the current inrush and hence the magnetization of the Ni cores. I'm not sure if it's 100 percent true but I think at least they help as I don't need a lot of time for my amps to sound open (and my horns are 106 to 110 dB efficient so there's not that strong a signal going through.
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I put switches on my Paramours. I just short from the transformer side of the Parafeed cap to the opposite end of the OT primary. With the primary shorted I wait 30s to a minute and turn the switches off. A SPST is all you need. I even got them from Radio Shack.
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Thanks, guys. Xavier, I've just not had very good luck with the ICLs in the past as they were had a fairly noticeable negative impact on dynamics. And with your ultra sensitive drivers I'm not sure you'd hear this on your system. BTW, totally awesome setup with the Edgar horns and MI drivers! If I only had a space big enough...
Grainger, I did think of this too, but for some reason I'm still not fully comfortable with this idea either, but I haven't completely ruled it out either. I willhave some room leftover in my larger chassis when I rebuild these amps with the Dowdy chokes, nickelEXO-145s and 6DN7 drivers, so maybe I'll add a time delay relay in side that has no possibility of being activated after the first activation. I also plan on using Neutrik PowerCons for the power connection, as they can function as a power switch as well.
I had an idea on where my CuTF caps might be, so when I get down there today hopefully I can get these installed and sit back and listen some more. And of course I'll have to hook the subs back up for the full effect.
-- Jim
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Jim,
If you are uneasy about leaving the switches shorted you can buy spring return switches. You will have to hold the switch in the shorted position for 30-60s then release it for each amp.
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No, actually I'm more uneasy about the possibility of discharging a fully charged parafeed cap through the cathode resistor.
-- Jim
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If I understand this discussion correctly, the output transformer primary shorting switch does not discharge anything. There is no DC voltage across, or current through, a parallel feed output transformer. (If there's no music, there is no AC voltage or current either!)
Ideally, you would leave the output transformer shorted until the tubes have warmed up and are conducting, and short it again before switching the power off.
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I have almost all the parts to build the SR45, except the iron.
Would the BH-5 work just as well as the TFA-2004jr? If I am not mistaken they are both 3K impedance.
I don't know how the BH-6 plate choke compares to the BCP-15 (40ma/50H)
Appreciate any advice
Thanks
Debra
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The BH-5 is a modified TFA-2004Jr, with slightly different coil geometry and materials. Electrically they are identical.
The BH-6 is a modified BCP-15-50mA, with slightly different coil geometry and materials. Electrically they are identical. It is gapped for 40 henries at 50mA.
For what it's worth, the BH-2 (SEX upgrade) is modified BCP-15-40mA, with slightly different coil geometry and materials. Electrically they are identical. It is gapped for 50 henries at 40mA.
The BH-xx products were developed by Mike to optimize cost-effectiveness, that is with refined but not labor-intensive coil geometry and materials, and in channel frames with solder tabs. All of the items mentioned are highly suitable for use in the original SR-45, and the performance differences are small.
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Thanks Paul, I appreciate it
Debra
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Paul,
If you guys end up selling this as a kit with a base plate could you please make it oversized? This would allow us tweakers to put much larger iron on top and fiddle around underneath. Maybe something on the BeePre scale?
Regards,
Aaron
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My new quote: "Every case is special, but there are no special cases".
It just doesn't make sense from a business perspective to compromise a design for a few, or to customize individual kits.
It is (in my opinion) more practical to handle different needs as a separate custom job. For example, for a modest charge one of us could place the layout on a larger panel with wider edges, and have it made by Front Panel Express and drop-shipped to you. That way, the manual instructions (including the pictures) would not need to change. Eileen could separately sell you a larger base in any of our standard sizes if you didn't want to make your own.
I know it seems a waste if you have some base parts left over, but the real cost of custom packing is much greater than the cost of the wasted wood.
Note, all the above are my own ideas on Friday evening with a nice cocktail in front of me; Doc B may have other thoughts next week so don't hold me to this!
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Lol, Paul I'm three glasses of wine in so I understand. What you are proposing would be ideal. I've been fooling around with a Paramount built idea using FS100 plate chokes and full 2004's and thinking how I'm going to fit it. I would happily pay for some level of ability to customize on the source end. As you know my SR45 build will be a one off too. If Bottlehead can support such customization, I am all for it!
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If a shunt regulated power amp enters our kit lineup, it may already be monoblocks on 10" x 12" or 12" x 12" chassis plates, so we will have very, very little room to grow any larger.
Also, an amplifier that is fully shunt regulated is the least flexible of all possible designs, as even something that seems as mundane as changing to a larger plate choke with more copper may have some undesirable consequences. The same goes for the BeePre and Eros, the refinement level of these designs makes them more sensitive to changing parts.
-PB
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Only a reckless bastard would change parts in an Eros, BeePre, of SR 45. I'm in all three groups.
BTW, I'll build three pairs of the SR45 Mkii whether it's a kit (please!) or a public design!
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Only a reckless bastard would change parts in an Eros, BeePre, of SR 45. I'm in all three groups.
BTW, I'll build three pairs of the SR45 Mkii whether it's a kit (please!) or a public design!
I'm in two of those reckless groups and intend to be in the third once released :). It sounds like the Dac is coming together and the SR45 isn't far from some of our minds. PB you are wetting our appetite for possibly another SR amp in the future? Maybe something with higher output? :D
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I'm not so sure about higher powered shunt regulated amplifiers. There are a whole ton of variables that get a little nutty when you try to move to a ~400V regulated supply that is capable of ~100mA.
We have a nice amount of data on running the 45 shunt regulated, we have little to none on much else.
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I was thinking that a high voltage b+ and three od3s in series could work. Since I use a power plant I have zero variations in power supply and that reduces the design problems and the need to leave headroom for high or low b+. That could give me a direct coupled sr 2a3 (not active loades, of course). Or a lower voltage b+ and a cap coupled sr 2a3.
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To a reasonable degree, it's the pass element in the regulator that demands the most attention. The TL431 is specified to be able to sink 100mA, and when you power on such an amplifier, the directly heated output tube is going to start drawing current before the indirectly heated regulator tube allows the TL431 to do much of anything (thankfully). This, of course, presumes that you aren't powering on the amp with no 300B in it (this is something we had to deal with for the BeePre).
The 0D3 stack will produce the voltage you desire, but the performance isn't sufficient for a power amp (in my opinion).
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ok -so one can order the tfa-2004 and the bcp-15--or the bh-5 and bh-6-would there be a preference-like deb i am putting parts together--thanks howie
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I don't think the differences will be night and day. But I have always had a warm spot in my heart for the TFA-2004. Maybe that's simply because I was the first guy to try it.
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I don't think the differences will be night and day. But I have always had a warm spot in my heart for the TFA-2004. Maybe that's simply because I was the first guy to try it.
So comparing the 2004 against the EXO-050 (full versions with the same lam stacks) in the SR-45 design (if you were to deviate from your stock 4k transformer) where would your money go? (As Mike does NOT offer a 4k transformer)
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I keep a pair of EXO-050s around too. It would depend upon the operating point, but the 5K primary is usually going to work better with a 45 than a 3K primary.
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mmmm---so somewhat non commital-but we are getting somewhere-the exo 45/46-is for a 45 tube-the 2004 is not necessarily so---
now maybe i should ask mike for a exo-45-in nickel with 8/16 ohm taps--and go with the dowdy chokes--wellll!!!!
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mmmm---so somewhat non commital-but we are getting somewhere-the exo 45/46-is for a 45 tube-the 2004 is not necessarily so---
now maybe i should ask mike for a exo-45-in nickel with 8/16 ohm taps--and go with the dowdy chokes--wellll!!!!
The EXO-045 is 8 ohm and the EXO-046 16 ohm. I know for a fact he has both stacked and ready to ship at the moment in XL (1/2 larger stack) size. Shoot him an email!
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reply to aaron johnson-do you happen to know if the exo-45's that mike has in stock are nickel or pinstripe?
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Both, EXO-046 XL in m4 pinstripe and EXO-045 XL in nickel. Just shoot him an email.
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Aaron-thanks--i just emailed mike for the EXO-45 XL and will see what happens-i asked about chokes on hand also-bcp-15 or the dowdy chokes-next to order will be everything else-from the power supply choke- power caps to tube sockets and everything in between-while i am here the SR-45 power supply shows a 10h chokebut does not show how much resistance-anyone know what i will need there-as for the cathode bypass cap-how low can i go there if i use a polyprophylene film-i may use them in the power supply also-thanks howie
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Hi Howie,
Do you have the paramour II's -- that is the amp that the sr-45 is built on, so I'd also guess that the ps choke would be the triad c7x at 270 ohms. I don't know the value of the cathode bypass cap, and I also don't know what board was used for the shunt reg board/c4s either and if that is still available or not. The amp also requires the pt2 power transformer. Of course I'm talking about the existing SR-45 here, not the new one that will be forthcoming, and I'm not sure which one you're talkiing about. If the latter, it is probably best to wait on the plate choke as this is going to be a critical part of the overall system voltage calculations.
But back to the original sr-45, BH is not releasing the schematics for this anymore, and it may be difficult to get another run of the pt2 power transformers as we just did one last summer. So, in short, a lot to juggle here and it would be premature to jump the gun on too many parts at this point.
A note about the dowdy as it applies to the original sr-45 -- Mike gapped mine for 60 mA instead of the usual 40 mA, which gives an inductance of 80 H vs. 125 H for the original. Mike also expllained that this actually provides better ac and dc balance in the choke specs, and results in a complex impedance that is more favorable for a opt with a 5k load -- such as the exo 4x models. Whether or not this choke, in either form, would be suitable for the new sr-45 is still a big unknown, so I'd wait until the design is out first.
I have the old version and will be using the dowdy gapped for 60 mA in conjunction with the EXo-145 in nickel -- a version of the exo-45 xl with an even larger stack and with the secondaries wound with litz wire, also somewhat more expensive than the standard nickel 45 xls.
So, if at this point you don't have the paramour IIs and instructions and parts for the sr-45 conversion, you'll have to wait for the new design, and nobody but Paul J knows exactly what that will look like yet.
Hope this helps,
Jim
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..., and nobody but Paul J knows exactly what that will look like yet...
Haha! No, there are a lot of things I haven't settled yet, so I certainly don't know what it will look like. We made some helpful decisions last week, and I'm working hard to make sense of them in a concrete circuit.
I do expect the design to center around the PC-3 and OT-2, same as in Stereomour. I'm playing with various ways to keep it flexible in terms of the kind of changes Bottleheads like to try, but I can't say yet what variations will be practical. Actually, I haven't even totally decided between a stereo vs. monoblocks implementation.
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Monoblocks PLEEEEEEEEEASE!
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Sounds like progress and I'm thankful for that.
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The 2A3 version of the Paramour II uses a 100uF cathode bypass cap. So does the 45 version of the Paramour II, non SR-45.
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jim -i bought the PT-2's in the group buy--and the soft start boards from BH-i have had the schematic for well over a year--so-hopefully sooner than later i will build these -i am planning a wood chassis-but this time i am going to use a metal under- chassis or sub-chassis- i wander through the hardwood stacks at the lumberyard looking for a few pieces of wood that light my fancy-after these are built i will buy a eros phone stage--and then think about tape deck upgrades-i have a akai deck but i keep looking at the technics and otari's on epay--grainger thanks for the answer-100uf it is
howie
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Hi Howie,
Ok, I didn't realize you had the pt2s, though I do believe PJ said that the soft-start boards are not suitable for the sr-45s, but I could be wrong about that too. :-)
I'm sure that whatever you build it will turn out really nice. Even if you don't build an sr-45, the soft-start boards, pt2 and dowdy and exo45xls should make a nice sooped-up paramour II 45, which is what I may do with my other pair of pt2s. And of course you can add a grid choke to either of these as well. Iron is good :-).
The dowdys are big so you'll probably want to build a somewhat larger chassis -- my plates are 8" x 11.5" OFC copper but I'll be putting the ac inlet and binding posts on the back of the frame instead of on top as is traditional BH style. These will be a real labor of love for me, as I'm sure they will be for you as well.
-- Jim
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i ordered iron from Mike today to build a pair of sr-45's
Debra
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Deb,
What did you order?
-- Jim
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deb -yes, what did you order-i ordered a pair of exo-45 xl in nickel- -i have yet to decide which chokes i want to use-howie
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Wouldn't the magnequest iron upgrade for the sex amp (BH-1 OT and BH-2 Plate choke) be ideal for the SR-45? IIRC the BH-1 was 4K.
Michael
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I went for the Paramour upgrade iron BH-5 full Ni and BH-6 plate choke. Mike said he can get that to me faster.
see Paul Joppa's post on the similarities of the BH iron to the magnequest iron for the SR-45
http://www.bottlehead.com/smf/index.php/topic,3000.msg36166.html#msg36166
Deb
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Deb,
If I didn't go with the dowdys, that's the set I would have gone with myself. With the dowdys in hand and the nickel exo-145s easily available, and the idea to use the tfa-2004s in the upcoming paramount 2a3s, the choice was easy. Now I have a second pair of dowdys gapped for 60 mA on order to finish the paramounts.
Good luck with the project -- I think you're really going to like these, especially with the solo piano stuff!
-- Jim
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thanks Jim
It will still be some time before I build them. Mike said it will take 8 to 12 weeks to get the iron.
In the mean time I will get the rest of the parts collected
Deb
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I' finished the first amp a couple of days ago and have been troubleshooting it ever since. It works now but the SR voltages are way off. I'm getting B+reg of close to 400v and a 34v bias. I've looked at everything mNy times and can't find the problem. Of course I already tried a different 6cm7 as well as new sets of 316k (2x 158) and 2490k resistors. Any clues as what might be the problem?
Thanks
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Now that I ordered the iron, now I have to decide what 0.1uf coupling capacitor to use.
The two I am thinking of are the V-cap CUTF and the Duelund Cast-PIO-Cu. The V-Cap is about half the price of the Duelund
Anyone have on opinions on which to use?
Thanks
Deb
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Hi Deb,
I'd probably go with the v-cap CuTF -- they're probably a good deal smaller, but also should you ever want to run EML tubes in the amp, the warranty on the tubes will be void if you use a PIO couupling cap, no matter how good it is.
I've heard the CuTFs and they are incredible and although I have some 1 uF CAST PIOs, I've not installed them in anything yet -- thinking I'll probably put them in the s.e.x. 2.1. And based on the generality of film caps having somewhat lower ESR than PIOs, my guess is that the dynamics and clarity of the v-caps would be a bit better, but how that would manifest in the real world is not something I've got any experience with in this amp.
Either one would probably sound amazing, but different. I like to think of the CuTFs as "warmly invisible" if that makes any sense -- all the nice tone of good copper caps, but just completely out of the way sonically, even if that is somewhat of a paradox. :-).
-- Jim
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Hi Jim
Thanks for the opinion. I will probably go with the V-caps
Deb
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Hi Xavier,
There were a couple of errors in the the Manual, I don't have what they were in front of me but you could search the old forum and find them but by looking closely at the photos and following the schematic, you should be OK.
First are the LEDs lit?, if so what do you read at pin 1 and 9 of the 6CM7? Pin 1 is the output and should be ~320, pin 9, the cathode should be ~13.5
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Hi John,
First let me accept that I am very stupid. Because the amp worked perfectly for 10 minutes and when I put a probe carelessly to take a pic showing the sr voltage I shorted b reg and killed something. So I replaced the board components and now the amp works but the two voltages you refer to are now 3
400 v on pin 1 and 34v on pin 9. The leds do light. I've checked and rechecked everything and can't find a problem. Thus my desperation.
Btw, I checked the forums (old and new) and indeed all the manual errors are documented.
Thanks for any ideas,
Xavier
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Ok, the voltage at the cathode Is too high, you may have lost the 431. Check the voltage at the the 2 set resistors R and R2B see if they make sense...John
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Thanks John,
I replaced all the board components after the "accident". I'll check the voltages at the resistors and report back.
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But now that you mention it, I checked the bias setting resistors for the 431 and they measure ok both in resistance and the voltages were ok according to the resistances (that is, the 400 v drop was divided proportionally to the resistances). So the most obvious suspect is the 431. I'll go ahead and replace it although it would be weird to get a faulty one. Maybe damaged it when soldered it?
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431's can be a little fussy. You want to look for 2.5V at the junction of the 2.49K resistor and your Vset resistors (IIRC there are two in series for the SR-45).
Also, you want to see some voltage at Kreg, but not more than 32. 34 is above the allowable amount for the 431, so if it was't originally dead, it may be dead now.
One thing to triple check is that the grid of the regulator portion of the 6CM7 is grouded. IIRC this is pin 8 (it's either 7 or 8). If this pin floats (like from a broken carbon composition), you'll have some regulation issues.
-PB
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Thanks Paul,
The grid stopper is ok and the grid is grounded ok. Yes, the voltage setting resistors are 2x 158k in series for 316k. That's what gets the 320v at the plate. I guess I'll replace the 431 and test.
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New 431. Old problem. Voltages are 394 at the plate of the 6cm7, 3.08 between the 316k and 2.49 k resistors and 46 v at the cathode of the 6cm7 (on top of the 431).
So the 431 is obviously not doing its job. The question is why. It's gotta be something deceivingly stupid.
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So checking the 431 resistances I found no connection from cathode to ground. Damaged board. A jumper wire and the regulated voltage is now 318.1 volts. Thank you guys. Good thing is I learned a lot about SR. Paul, let's think about designing an sr ps for that soul sister we've been discussing in the valve section of the board!
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Ladies and Gentlemen.
I'm listening to one amp, in mono, with a lesser Altec speaker (a Patio speaker with a coated 755E driver in a small platic cabinet). And I can, without any doubt, declare that the SR45 redefine my references. The old references are destroyed, smashed, slain.
The amp in question has exo 050 Ni opts and Ni grid chokes. No fancy parts or else.
It has the ultrafamiliar (to me) BH tones and sweetness. But the detail is a notch above anhthing else. But above all the way the music "flows", wooooow.
PJ and Doc, you are geniuses.
I have to make me three pair of these for the main system. ASAP!!!
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Xavier, I'm glad you hear what we do! :^) Made some progress the last day or two in the new design. I'm ready to prototype the power supply and see if my idea is actually workable...
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If this becomes a special run it will be the "back to work" present to myself. Paully's 45 amps really sing. I'm sure the Orcas in my ~300 sq. ft. room will reach volumes louder than I could stand.
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Best amps ever Grainger, you deserve a pair after all your hard work :)
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Xavier, I'm glad you hear what we do! :^) Made some progress the last day or two in the new design. I'm ready to prototype the power supply and see if my idea is actually workable...
:):):):):):):):):):)
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Xavier,
Congrats on getting the first one done. I agree they are really special amps. I'm going to get mine back on a 24/7 schedule today after a few days of being out of commission (me, not the amps.)
I have to say I've never had so much fun with DIY audio, and the rebuilds are going to be even more fun.
Great stuff!
-- Jim
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Thanks, Xavier!
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Quick update. A couple weeks ago we were talking about the SR45, and Doc B said "if you're going to do a shunt reg'd amp, I want to see it done right and d@%# the cost!" - or words to that general effect. So, after my first enthusiasm led to a $12,000 kit :^) I've been working on something more reasonable. I have a pretty good idea now of where I'm going, and a fairly detailed general layout. I have always wanted to regulate the filament and heater as well as the high voltage, and doing that always leads to a lot of heat under the chassis, which is already the biggest problem with the SR concept. So I'm now sketching quite a large amp with a better thought-out cooling flow and lots of heat sinks. I'm aiming for really long-lasting parts as well, and delay relays for startup and shutdown sequencing.
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I like the approach!
Do I assume 12 x 12 layouts? With three pairs that would mean some serious footprint!
I would like to start sourcing iron. I have the 404s already. Will the bigger chassis allow for, say, Dowdy chokes, or good old BCP15s?
And finally, I guess it's cap coupled? 'Cause then grid chokes would be on the list as well.
It looks like a new car will need to wait a couple o' years!
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Thanks for the update Paul! Has the project changed from a partial kit to a full kit?
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At this point, I am not allowing for non-standard iron. The chassis is quite large (I'm leaning to 10x16...) but more than half is power supply - there is a little room but not much. Custom chassis plates might be an option. There are several other related developments in the works but I won't discuss them until we have a consensus :^)
Yes it's cap coupled. Much as I like direct coupling, it adds too much voltage to the power supply - the shunt reg already adds some. Really good caps are available these days!
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At this point, I am not allowing for non-standard iron.
I think that's a great choice, it would be impossible to design a kit that will work with four different output transformers and five different chokes...
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Paul, is the 10x16" layout a stereo mono block design?
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"it would be impossible to design a kit that will work with four different output transformers and five different chokes..." No need to do that. As long as my three pairs of TL404s work I'm fine.
Seriously, you know I'll get three pair of these. Using my 404s would just be awesome. But I understand that optimizing the amp for a certain output impedance requires important changes to the ps. So I can only pray to God above that you are designing for 5k!
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Hmmmmmm, I have a problem with this also that goes a couple of ways. I above all respect and admire what you all do as designers and as a company and the quality of your products has redesigned my system and given me considerable pleasure.
The decision as was posted earlier to use a 4k opt is a little hard to swallow if we are unable to change the operating point. This amp was never meant to be a main stream item nor will most people be able to live with 2 watts output. For those of us that can live with it and want to invest a considerable amount into two watts the choice of 4k leaves us zero options for other iron unless we have it custom wound. Mikey already said he wasn't doing it and to change it to a 5k. There are numerous options in 3k and 5k. Will you guys please reconsider the end user and change this to 3k or 5k?
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Like I said before, I think this design will be perfectly optimized for the iron we use, as soon as you go to something else, you run the risk of the design not being ideal for the iron.
No compromises means no compromises. All this discussion of which MQ iron you want to go into these amps makes the assumption that our iron will be inferior, which may not be the case in this instance.
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Paul that's not what I'm saying. I'll use myself as an example. I've exchanged emails with you and PJ both about using the SR45 as a platform for a Stax headphone amp. PJ helped me find the right iron and Sowter modified a preexisting 5k design to make it work. In the 5k range along there is off the shelf and custom options from 2 Ohm to 500 Ohm output in every lamination under the sun. With the 4k design there is one, yours and where it may be outstanding iron there is no room to be a Bottlehead and experiment.
I'm beginning to feel that you all don't want us to experiment with this amp and that defeats the entire reason for my initial purchase. If you don't offer us the 5k option, I am out of luck and will need to find a pair of the older SR45 amp that can make work for my particular need or scape it all together.
This being said I will still probably purchase one pair of the new design.
Does Bottlehead intend to release iron in different lams at some point? Are you encouraging winders to adopt your 4k spec?
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OK. I guess I'll wait and see what you come up with. If you use no compromise iron I guess I can sell my three pairs of TL404s (and I'm pretty sure they'll fly). As long as the iron has 4/8/16 ohm taps and I'm allowed to play with the parafeed cap sizes (my crossovers) I'm fine. Otherwise I'll have step aside.
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I would expect the amp to work extremely well with any load impedance between 3K and 5.5K.
I have tried to let the Forum in on what I am exploring as possibilities; I apologize if I have given the erroneous impression that these are commitments or actual product descriptions. To be clear:
***** there is no final product design yet *****
and everything I have said so far is subject to change. My post yesterday is an example - the design has taken a major jump in perspective. This has been creeping up on me for some time, and is the primary reason progress has been so slow the last year or so. My original intent was to modify the original to resolve the excess heat and reliability problems, optimize the operating point, and add DC filament power since an amp of this caliber should not hum, even on extremely efficient speakers. Every solution I came up with has had problems of its own, mostly because my thinking was self-constrained to just modifying the original, flawed (in my mind) design. Once I started to come at it from the idea of "how would I do this to get it right?" it became clear that a significantly different design would have to be the answer.
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Hey Paul, I don't thinks there's need for apologies. You're being very open as to where you're standing and we appreciate that. I guess some of us are so excited with this new project that we can become a PITA with our posts. Please take all of them as suggestions. In the end you know we'll find a way to mess around (while not necessarily improve) your final product. I think part of the fun of building BH kits is that. I'd never replace my BH amps with "finished" products for that reason!
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Paul, i can't conceive of my sr-45 being flawed. It is one of the great pleasures of my meager existence! But if you can improve it in some way i am all ears;)
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I guess I haven't addressed the impedance question very well yet - I was feeling pretty crabby last night (for which I apologize to anyone who might have felt offended. Completely unrelated reasons.)
Anyhow, in my opinion, or according to my analyses depending on how you like to phrase it, 4000 ohms is as close to ideal as you can get for a 45. A 3K load exacerbates the already poor damping factor of the 45. On the other hand, getting full power from a 5K load would require a higher plate voltage than the tube is rated for.
By designing at 4K, a range of about 2800 to 5600 will work quite well (I calculate that as the square root of 2, multiplied by or divided into 4K) - that is, they will all produce similar power and distortion, with a slight tradeoff of higher distortion and greater power at the lower impedance, and vice-versa at the higher impedance. In my opinion, this is the best available compromise; those who wish to use different iron are welcome do so as long as they can figure out how to mount the components safely and effectively - and don't expect Bottlehead to guarantee the result! :^) In many cases that will require a new, larger chassis plate - but that's always been the case, and probably always will.
In the original SR45, I jiggered the operating point (lower voltage and a little too much current) to work best with a 3K load, since that was the only available quality iron for the Paramour at that time. Stretching that to 5K was a bit much, so I offered some adjustments, mostly just reducing the current. It increases the distortion a bit, leaves the power unchanged, and extends the tube's life a bit. I'd like to stress that all the above are quite small effects - I think most audiophiles might hear them but would be hard pressed to choose which is best.
Incidentally, in my current draft layout there is more room than usual for capacitors. But as I said, I haven't even shown this draft to Doc B yet.
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It takes way more to offend me!
Something tells me these sr45s will be the last amps I'll ever need. The challenge will not be fitting the TL404s but finding time to build the three pairs instead!
Saludos
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Paul no offense taken! I hope I didn't offend you!
Thanks for the detailed clarification on impedance. I'm really looking forward to your final product!
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I built my SR-45 with the BH-5, and BCP-15's, however I may not have wired to the speaker, as Paul had intended. I wired for highest load.
I acquired a pair of nickel EXO-45's, put them in and like them. Understand, I like nickel and run them full range. I am not asking them for the very deepest bass. To that end I often run them with no cathode bypass cap on the 45...John
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having ordered my-output transformers from magnequest-power transformers from bottlehead-triad chokes for power supply via [i forget where] and plate chokes from heyboer{using jim redmonds 60ma. 80H suggestion}-i am getting ready to order the rest of the parts i need-my question concerns the power supply caps which show to be 47uf--is there any benefit in increasing the value of the power supply caps
thanks howie
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The value of the 450v capacitors in the power supply is not critical, once the choke has replaced the 270 ohm resistor and especially in a regulated PSU. I wouldn't go lower than 25uF, myself, or over 220uF, but the true answers come from PSUD (the simulation software) and from your ears.
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it seems best results using psud are 47uf for c1 and150uf/ 200uf for c2 --i am unable to put the first 470k resistor in place per the schematic but psud puts a 10m in series right after the rectifier for me-which after changing the values of this R1 around the 10m seems to be the ticket-is there a way to duplicate the power supply exactly -i seem to be able to insert only a circuit not a specific component and not parallel to c1
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The 470K resistors are bleeder resistors, I don't include these when modeling in PSUD
Debra
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ok!!!-i managed to removed the one 470k--never having fooled with psud what exactly am i looking for-what i have on is a 10m resistor in series rt after the rectifier -a 47uf cap the choke then a 200uf cap with a load of 60ma-the caps are across the b+/b-this gives me on the graph simulator--at 0 a nice slightly upward curve then a 45ish degree line and then a gentle curve that then flattens at just below 400v--there does not seem to be any info to inform one of what it is we are looking for--i can infer from here and there on the net but nothing specific-it seems what i have modeled is correct as the curve is gradual with a steep but inclined climb and then leveling off --this is a little exasperating but a great deal of fun--realizing no-one has seen my yard -but i have lots of gardens and yard-trees to trim-- windows to paint--but nooo!!!! i sit here fooling with psud
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Yeah, PSUD has a steep learning curve. Two things I look for:
1) no ringing, or at least not very high or for many cycles. This usually happens in the first few seconds.
2) To check the ripple, model after a delay of a few seconds so the voltage has reached a steady state. Then you can see the ripply, and the table will show max and min values.
There are extensive discussions (and flame wars - wear your flak suit!) on the TubeDIY board at Audio Asylum. There are kernels of wisdom there, but more chaff than wheat. For a SR amp, the regulator will take out most of the ripple anyhow, so my advice is a quick check for ringing (you've done that), then head to the garden in the spring sunshine.
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thanks paul--i have one more question-the psud puts a 10m ohm resistor in right after the rectifier-i take that this is correct-what is the necessary wattage for this component
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Change from an RC filter to a C filter, and the resistor will go away.
Unless you are referring to the capacitor's ESR, which you can find in the cap manufacturer's data sheet.
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i got it --thank you--
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It's been a while. Can you fill us in on your progress Paul when you get a chance?
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It's been a while. Can you fill us in on your progress Paul when you get a chance?
Good timing; I was just going to spend some time today pulling together my scattered notes - I've been out of town a good deal lately, and grabbing a few free hours here and there to work on aspects.
This thread has a bit of a split personality, so in this post I'll only talk about a the new amplifier design being developed which will implement the fully shunt-regulated high voltage power supply concept. At this point, it is an entirely new design, not an upgrade of the original limited-production semi-kit of several years ago. Doc B. and I have conferred extensively on where to go with this, and concluded that the regulated approach should be matched with an equivalent level of performance, reliability, and utility.
One consequence is that this design is optimized for performance, rather than being an experimental platform. Not that you can't play with it of course, but we'll put better, more expensive parts in without worrying about making it easy to change them. Here are a couple examples:
1) All the power supply capacitors are going on a single large PC board - the "capacitor farm". They'll be premium long-life parts, and the layout places them away from the heat-generating parts for longer life. Probably on the same board there will be a set of sequenced power control relays and timers.
2) The cathode bias and the master current source bias resistors both get hot and dissipate a lot of power. So this time I am moving them to a second "heat-sink farm" board, well removed from the capacitors and with a large cooling vent immediately adjacent. At this time I expect to use Caddock TO-220 resistors on large heat sinks. It will be difficult to replace these with (for example) your favorite Mills NIWW, but on the other hand the Caddocks are damn good resistors to begin with.
3) On the other hand, I have allocated a large space around the tubes for the capacitors that carry signal current - interstage, parafeed, and cathode bypass. Those will be easy to swap out - this is still a Bottlehead amp, after all!
The performance improvements are relatively small. Based on the recent BeePre work, I'll try a second generation regulated filament power for the output tube, along with regulated heater power for the driver/shunt regulator tube. That should reduce hum and noise, and also overall operating point stability - which is IHMO a major part of why regulation sounds good. The operating points are optimized for performance, without compromise for available voltages or a variety of transformers and chokes. Again, not that you can't play around with iron, just that the design is built around specific parts. I intend to put in some better-quality signal capacitors from the start, as well.
For convenience, I want to have output impedance switches and input level trim to optimize system balance. And the power sequencing relays and timers will protect the output transformer from being magnetized by startup and shutdown transients, so the amp should sound good very quickly - no more "run it with music for 30 minutes before critical listening"!
For reliability I have already mentioned the cooling flow and parts location design. There are a lot of electrolytics in the low-voltage power supply, but with temperature control and careful parts choice (and some conservative, mil-spec design practices) you can get a theoretical lifetime of well over 100,000 hours. The sequenced power will extend the life of the tubes, as will regulating the filament and heater voltages.
Appearance is still being worked on. I'd love to have all the connections on the back panel, and a hefty thick front panel with only the power switch, perhaps with wooden side panels. It looks like a basic chassis plate 10 inches by 16 inches will accommodate the layout fairly well, and could be done optionally sideways for rack mounting if anyone actually wants that. But at this point, all that is speculative.
I should mention that there are some other features and directions being worked on; I can't go into them until I get some more research done, but the bag of tricks is not yet empty!
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Thank you Paul for the update :)
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Wow sounds like its going to be amazing! Cant wait Paul!
I would like to request grid chokes in the amp or designed so they can be added later based upon the transformation of my current sr-45 when i added them.
I am listening to it now and it is just so good i dont know what to do with myself:) its hard to listen n not dance! I put the subwoofers n amp for sale today - no need anymore...
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Hey Taran - what are you using for a coupling cap upstream of the grid resistor?
I'll give that some thought - with the longer chassis it may be possible to find a quiet location for a grid choke.
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hi Paul... not Taran, but using MQ HN grid chokes in the SR-45 too... using a RelCap TFT for coupling... the grid choke were a noticable improvement...
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Im using a vcap cutf coupling cap. I think the grid choke was the biggest improvement i made with parts. Going from a russian teflon to vcap was 2nd.
I put in cobalt grid chokes. I should compare to the nickel. I put ni grid chokes in sex amp and PDG amp but not as noticeable a difference.
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Awesome Paul,
Very much looking forward to it.
The Mexican Bottlehead community has been discussing this on our own discussion "forum" (a crazy emails chain) and thought that the BeePre experience could lead this project to become an SR300B (2 watter though).
Saludos
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There are some incurable tweakers here, aren't there?
What I meant was, what capacitance - not what type of capacitor. Remember, I do have an engineering background ... I still like numbers when I can get them!
re: the 2-watt 300B ... many things are under study ...
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Lol ya 0.1uf. Meant to include that...
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re: the 2-watt 300B ... many things are under study ...
:) :) :) :) :) :) :)
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As long as we're pushing the envelope how about a Quickie (ie. battery) BeePre.
Michael
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2-watt 300B , that could be direct coupled....couldn't it?
Maybe with dht driver?
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Nah, direct driving would make the project much more complicated. And where would we use the grid chokes then? :)
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I too think that the nickel BCP-16 was the largest improvement.
Using mine behind a .22 Russian K40
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Adding a grid choke should the value of the coupling cap increase?
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As long as we're pushing the envelope how about a Quickie (ie. battery) BeePre.
Michael
Quickie IS a battery BeePre! Well, it's a DHT single gain stage with no output transformer, straight from the plate - the simplest possible tube gain stage. You could try a Type 31, which is a real triode instead of a triode-wired pentode and needs 2 volts for the filament - a single-cell lead/acid would be appropriate, and I think they exist in D-cell format. It would probably be happier with more plate voltage, but should work at Quickie conditions. Said to be EXTREMELY microphonic but I haven't tried it or heard one.
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Adding a grid choke should the value of the coupling cap increase?
0.1uF works out to be pretty reasonable on Mikey's grid chokes.
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:)....of course... its all in the numbers.... 0.1uF also.... one of these day I'm gonna buy some V-Caps....
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In my amps the stages are RC coupled and the grid chokes go from grids to ground -- I thought this was thepreferred way to use a grid choke as opposed to LC coupling? Any advantage either way? I would assume with the grid-to-ground config the value of the coupling cap would not have to change.
Speaking of the split personality of this thread, might it be useful to have a separate thread either for the legacy or new design -- I can see new folks getting pretty confused by this thread at some point in the future.
-- Jim
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Jim, I am not clear on what you said. Normally the grid choke would replace the grid leak resistor (usually 249K or 270K in Bottlehead power amps), from grid to ground. (Actually I mean from the grid stopper to ground; nothing but the stopper actually connects to the grid pin.) I suppose that, by analogy with how we describe power supply filters these days, you might properly call these C-R or C-L coupling rather than the traditional RC/LC terms.
There are two main technical effects of a grid choke:
1) Since it has inductance, it will resonate with the coupling capacitor. That resonance is damped mostly by the effective parallel resistance of the choke, which comes mostly from eddy-current losses. There is an argument for leaving the grid leak resistor in parallel with the grid choke so that a known minimum amount of damping is provided. This resonance means the bass response rolls off more steeply while remaining flat through the audio frequencies, so faster recovery from transient overloads is likely to occur.
2) At midband frequencies the impedance of the grid choke is higher than the resistor it replaced. This places a lighter load on the driver, possibly reducing its distortion. Leaving the resistor in parallel will eliminate that effect.
I have not done any measurement or listening to evaluate this tradeoff - which is why I wanted to know the capacitance that seems to work. If there are experiments with leaving the resistor in parallel, I would be most interested in the results as well!
With the longer chassis, and the DC heater supply, there may be a suitable location for the grid choke, near the driver and far from the power transformer.
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Paul,
Ok, third time on this later when the oxy codone wears off and I'm a bit more focused.
I'm just going to avoid posting for a while until I can truly grok this :-). I think we're saying the same thing but I thinkk I used the wrong terms in the wrong places.
-- Jim
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Ok, we are saying the same thing, except you have a grid stopper in there and I'm not sure I remember seeing one in there -- unless it is the same as the series RC coupling combination. But the amp is downstairs and has juice on it, so I'm not going to go poke around right now. And yes, now I can see why it would effect the RC resonance point.
Thanks for getting me on the right track.
-- Jim
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Me again, any updates Paul? The Bottlehead team has been busy with so many releases lately but my eyes are on this baby!
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Nothing much. I'm struggling with the wiring plan, since I moved parts away from convenient locations to locations where they will remain cooler and last longer. The amp is part of a larger plan, and there are some issues with making sure that derivative designs are going to be workable.
I think I may have a few too many balls in the air and will have to drop a few ... :^)
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Lol, as long as the new SR45 stays in the air, I'll be happy. Electrolytic caps are cheap and if I have to replace them every 2 to 10 years, I can afford that. Mastery need not be achieved on v2, just improvement and a step forward from v1. ;)
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I know others are watching and that Paul and team have got a lot on their plates but I'm going to bump this thread every two weeks to keep interest and check on progress. So any updates Paul?
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Thanks, Aaron.
Not much yet, except I've shuffled the parts around quite a bit to simplify the wiring. There are still 16 or so wire bundles, mostly 2 wires each, of 4 different compositions - but at least they don't cross each other any more. And I put most of the parts in a BOM spreadsheet so I can guess about the cost.
Premium caps are EXPENSIVE! I may put all the PSU caps on a separate board, and let the tweakers make their own boards for fancier caps. Between the DC filaments and the turn-on delay logic, there's a lot mroe caps than usual. Incidentally, I'm keeping the critical caps off the board, it just has caps with no signal voltages.
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Thank you for the update Paul :)
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Two week follow up post checking on progress. Paul, I hope you are on or going on vacation shortly.
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PJ is indeed out of town at the moment.
-PB
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With everyone back this week, how about an update on the status PJ?
Thanks,
Aaron
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Status? Same as when I left town. (Just got back last night :^) Ask next week - I hope to get some time on this project. There's a lot done in my head that isn't written down or sketched out yet.
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Not quite a week but close enough:) how's it comming along Paul?
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Got some time Thursday and today, and finally got a lot of my thoughts down as actual schematics with parts values (!). Four pages and counting. I've also tentatively laid out which functions go where on the new physical layout, so I can draw the actual wire bundles. Once that's done, I can start doing the detailed PC boards. (Don't worry, all the signal voltages are off the boards - it's just power supplies and sequencing logic.)
One of the things going into this design is an RFI filter at the power input; I'm following Buddha (the late John Camille) in using a commercial RFI filter followed by a homebrew lower-frequency filter that gets down to 2kHz. I've gone back and forth on how to do this, and how complex to let it get, but that's where I am now.
The power and protection sequencing was a bear since I didn't want to use digital counters. At this point there are four LV regulators and three relays in each amp. I had worked it out a month or two ago, but getting the details down on paper (and fixing my hand-waving!) was a chore.
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I'd better start saving!
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Me too! I'm getting more excited about this project with every update. Thanks for not giving up on it Paul!
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It's time for the two week status report. How's it coming along Paul?
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Good progress this week - as usual, once I see the circuit and/or layout on paper, I make changes ... Hope to get some PC boards laid out this next week or two. I need to mock up the power supply to confirm voltages and delay-relay sequencing, before getting into the actual audio circuit - but I'm already looking at some options for the driver bias.
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It's been only a week but how about an update Paul? You seem to be moving along on this project.
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No update today; too much real-life business.
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OK, a bit of progress finally. Today I ordered two chassis plates, on which to build the prototype pair. Since this required enough certainty in PC board layout to position the mounting holes, which in turn means finalizing the specific parts to be used, that's actually quite a bit of work - but Front Panel Express has a sale that I didn't want to miss! The plates were $180 on sale, FWIW.
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Thank you very much for the update Paul!
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I've started refining my horn system. Having had it off for a few weeks has helped me realize where a couple of improvements could be made, mostly positioning and crossover related. I will still modify the three pairs of Paramounts to use one Co, one Ni and one series feed with Ag primaries and secondaries with the WE. And when I install the horns back, hopefully early next year, they will be powered by three pairs of these new sr 45s!
Pd. Please Paul, when designing keep in mind my tl404s!
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"I'm sorry, Xavier, I can't do that. Opening pod bay doors ..."
Seriously, the chassis is laid out for the OT-2 and OT-3; there's enough room for a TFA-204Senior but that's it. Since I don't have drawings for the TL-404, I can't say whether it will fit or can be oriented correctly.
Of course a custom chassis plate is always an option. Not an inexpensive option, since it would not be laser-cut, but an option. Let's get something working before we start to re-design it for different parts!
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Hey Paul, let's say You give me the right op for 5kband recommendations to use an autoformer and I'll take care of the chassis and layout. I'm buildin three pairs and plan to go fully overboard.
And of course you first have to have a workin thing!
Thanks!
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Space enough for three pairs of sr45 with tl 404 :)
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You might want to keep those TP tapes farther away from power transformers. A power transformer is sort of a mild version of a tape demagnetized.
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Thanks for the advise. I just put them temporarily while I rearrange everything. I knew that they shouldn't be close to the amps but didn't know the reason. The system is not working and don't plan to energize it with the tapes there. They look cool there though don't they?
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Here's a 404 on top of a SR. Exact same mounting hole positions although maybe stacked perpendicularly ?
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"...Alas, 'tis just as I feared..."
The coil axis is aligned with that of the power transformer. The transformer must be rotated 90 degrees to avoid magnetic hum pickup, so the chassis width would probably need to be increased.
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Well, my return to horns next year will prove to be an interesting one!
Thanks Paul, learned a bunch with this exchange. Won't bother you more on this subject for a few months!
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I think Xavier just one-upped my CD cases.
No offense meant or taken, Xavier! Those are beautiful shelves. BTW, my Temp Area Engineer job ends the last of August. Then I will be picked up for another project in 4-8 weeks.
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Here's a sketch of the chassis plate. There are two narrow vertical PC boards between the transformers (right) and tubes (left). The one nearest the vent is the heat sink farm; the other is the capacitor farm. So far I've only laid them out enough to place the mounting holes.
Yesterday I emailed Clark about making some nice bases; hopefully I'll talk to him in person before I go on vacation.
Do understand, these are for the proof-of-concept amps (which will likely end up being my personal amps :^). The final design may or may not be different!
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Thanks for sharing! I thought you had said 12x12 but that's obviously not the case!
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Nah - somewhere I read that there is actual science-type evidence that people like the Golden Ratio (it happens to be very close to 2/3 of an octave so I use that) - so I built this on a 10x16 plate.
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Paul,
If I'm reading you right you're talking about a simlar orientation as the paramour/paramount but with the signal section all at one end and the power section at the other. I've recently been playing with the idea of making my rebuild of the sr-45s on a narrow and deep chassis to accomplish the same thing of keeping the psu at one end and the the audio section at the other end -- keeping the noisiest parts away from the sensitive gain stages, the audio signal path as short as possible, etc. Thinking something like maybe 6" wide and maybe 18"-20" long. Can't claim originality on that one -- see the audio note kegan and kegeki amps as an example. Of course this is nothing like a golden ratio but could be a nice alternative to having the entire circuit built around a central power transformer.
Not sure this will work yet, but after I cut out some cardboard templates and arrange iron and caps on them, then I'll have a much better idea, but so far, just juggling this stuff in my head it not only looks possible but also that it could easily accomodate a really large pf cap and large ps caps and provide a nice quiet place to mount grid chokes.
-- Jim
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I built my SR-45 on a 10"X18" base as a stereo amp. Plenty of room. I think there is like, 12 bits of iron infesting it at moment...John
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Hi Paul, how is the first build coming along?
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It will be a couple months. I have the chassis plates in hand, and the PC boards about half done - but I'm off very soon on a 6-week vacation to celebrate our 40th anniversary.
On the plus side, Doc B and I conferred Friday for some time to make sure we are in agreement on the design philosophy and direction - I am making a number of technical improvements over our usual practice, almost a new level. Doc B is happy with this experiment, so I have a green light right now.
There will be updates in late October.
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Congratulations on your 40th, have fun on your vacation...John
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Paul,
Happy anniversary have a great trip!
Debra
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Enjoy your trip! 40 years is a long time! You guys deserve it!
My grandparents made it to 69 years. People would ask my grandmother had she ever thought about divorce. She always said no never but there were plenty of times i wanted to kill him;)
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Happy anniversary Paul! Have a safe trip!
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In the existing design, what would be the ramifications of changing from a plate choke of about 360 ohms (what I understand is what the bpc 15 is) to something a bit higher, say 50 ohms more -- DCR is what I'm talking about here.
Any places to make other adjustments? OPT will be 5k.
Just about done with planning the sr-45 rebuild and will layout and start machining the top plates this week.
-- Jim
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Hi Jim, The increased DCR will drop a few more volts across it. So the voltage at the plate of the 45 will be 10-20V less...John
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John,
Thanks -- with my higher line voltage I'll probably not have to do anything to compensate then.
-- Jim
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Just finished one SR45 amp so far. It is a very nice sounding amp!
Now to start on the second one
Deb
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Congrats Deb! Keep us posted!
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Hi Deb,
Glad to hear that this is under way. Any details to share? Have you considered using the 6dn7 as a driverr tube? Pobably too late now. What are you using for iron? Purple, I assume :-)
-- Jim
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I built the amp from the schematic of the SR45 and referred to the Paramour II manual for some of the construction.
Iron is:
Magnequest BCP-15 40ma/50H
Magnequest BH-5 Nickel outputs
Magnequest Grid choke
Triad C-7X Power supply Choke
Coupling capacitor:
V-cap CUTF 0.1uf
Parafeed Capacitor:
Clarity Cap MR 10uf
EML mesh plate 45 tube
I built it on a Paramount chassis panel
I have only listened to the amp in my lab, I will put them into my regular system when I finish the second amp. I have been very impressed with the sound so far. It made the old Klipsch Heresey I have in my lab sound very smooth, nicer than any other amp I have tried them with.
When they are both built and broken in a bit I will post my impressions
Deb
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Hi deb,
That should be a really nice setup with the Orcas and or your fe-206 speakers.
I too just can't get past how beguiling these amps sound, even with OS american 45s -- I'm getting very impatient waiting for my 98 db speakers to arrive and I've decided to put off any new amp construction until I've got the sr-45s tuned /voiced to the new speakers, using the existing chasis as a test bed for those experiments. I also have a backlog of other projects to keep me busy through the cold weather months, and by then I should have a very good idea and detailed plan for rebuilding the sr-45s in a new chassis with a slightly modified layout. These are some seriously good amps even if PJ doesn't seem totally happy with the design.
If you want a couple of nice heat sinks for the sr/c4s board, PM me and I'll send you a couple.
-- Jim
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Thanks Jim!
I too think they will sound great with the Orca's
Like you I have way too many projects, maybe I will have time to finish them this winter.
I also have too many amps, ok that is a good thing :)
I will PM you about the heat sinks, the ones included with the SR45 kit get quite warm.
I never thought this thread would get this big when I started it, it has over 17,000 views now!
Deb
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The SR45 amps are done!! They sound great, probably the best sounding amp I have built to date. Not as forceful as the 2a3 Paramount, but more detailed and refined. Very, Very smooth sounding amp, a great match with the Orca's! They will only sound better as the components break in. Grainger, I know I should have burnt in the V-cap CUTF :-(
I have some film capacitors on order I want to replace the 47uF elecrtrolytics with.
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi284.photobucket.com%2Falbums%2Fll38%2Fdebk3141%2Fa9f7233c-f71f-49ed-a198-1344df9d8bd9.jpg&hash=5465d90c520987d4f9ac35e01b09cbe8da4b622f)
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi284.photobucket.com%2Falbums%2Fll38%2Fdebk3141%2F2d837bdb-e0e5-4f1c-86b4-eeeb60648e70.jpg&hash=eae7599c5b571567bd7eede1a78006525de88d1a)
Deb
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Hi Deb,
looks nice, did you find a spot for the grid choke? You are using the same iron complement as my current amp, no V-cap though :(.
I don't remember if you had a chance to hear it at the Bottleneck meet a a few years ago...John
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John
The Grid choke is hidden by the large parafeed capacitor, it is mounted with the holes that the cathode resistors in the Paramount would have used.
Yes, I remember your amps, they sounded wonderful!
Deb
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Deb,
I wasn't going to harass you about burn in.
But I was wondering when we would see the purple pictures.
Nice build, good looking amps.
I take it that the 47uF is the cathode bypass?
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The 47uf's are the power supply capacitiors
Deb
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After a looong and scary delay at customs my SR45 are right now being set up at room 845 at RMAF. So don't take Deb's words for granted and go and listen to them :)
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Iv'e been listening to the SR45's quite at bit.
they are sounding better and better every day. I am amazed how much more I can hear. I can decern individual instruments in the music, amazing detail and clarity.
Very impressed I really like the sound of the 45 tubes
Deb
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Hi Deb,
Great to hear! How's the solo piano material sounding?
BTW, my wife was curious to see what I sent to you, a woman, the other day :-).
-- Jim
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I haven't been following this thread very closely. So are these superior to the Paramounts? How much work goes into them? Parts easily available?
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The solo piano material is amazing. the closest to live I have ever heard. I continue to marvel at the detail and clarity these amps have.
That's funny, hope your wife didn't give you a hard time :-).
Deb
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I haven't been following this thread very closely. So are these superior to the Paramounts? How much work goes into them? Parts easily available?
I personally like the sound of the SR45 better than my 2a3 Paramount. The SR45 is a modified Paramour 2. As for parts I was lucky enough to have someone sell me an unbuilt SR45 upgrade kit.
Deb
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Does it sound better than a 45 modded Paramount?
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What Power Transformer did you use? I can't quite make it out from the picture.
thanks,
David
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Never heard a Paramount modded for 45's so I can't compare the two.
The transformer is the Bottlehead PT-2
Deb
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And the s.e.x. 2.1 iron upgrade kit would do nicely for the iron, plus a triad c7x for a psu choke, however... the real issue is that the shunt reg design has been pulled from the BH web ssite as it is BH intellectual property and PJ is not totally happy with the design. So, it really comes down to paramour II and this shunt reg board with minimal changes and you have and SR-45.
We did a group buy of the PT2 power transformers a bit over a year ago and I have no idea if BH has these or will let you copy the design of the shunt reg board, which you'd have to make from scratch as it was based on an old version of a C4S board -- at least I am not sure if one of the new boards could be made to work.
More than likely you'll have to wait for the new version of the SR-45, which may or may not become a product -- that's all between Doc and PJ.
I think there were only something like 10 or 12 of the sr-45 upgrade kits ever sold, so they're pretty rare out there.
HTH,
Jim
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Well, if it makes a difference, I'm still in the market for Paramounts, and if the SR45 is really a step up (with proper speakers), then you could put me on the list for those instead. I'm sure there would be more interest, too.
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Maybe in the Spring I can do the comparison, or maybe Sail Doctor can take his 45 paramounts over to Clark's place and compare to the sr-45s over there.
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I've been enjoying my system for the some years, haven't been soldering or posting- hi to everyone! I bought one of the original SR45 kits with the intention of picking up a pair of the PT-2's, but it looks like I've missed that boat, and the later group buy. Is there another current substitute for it? I also have the iron to build 45 direct-coupled amps that I haven't got around to, with the PGP 8.1's. Maybe I could make that an SR-45 instead? I also have some of the Exemplar Audio driver regulation boards, but no directions for them.
Is the new SR-45 project going to be a complete amp, or an add-on board for the regulation?
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Maybe in the Spring I can do the comparison, or maybe Sail Doctor can take his 45 paramounts over to Clark's place and compare to the sr-45s over there.
That would be great!
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If we can get Sail Doctor to bring his 45 Paramounts over to Clark's, I can bring my SR-45's with Paramount output iron along for comparison.
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Wish I can e there
Love to hear the SR45 with Clark's Uni speakers
Deb
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...
Is the new SR-45 project going to be a complete amp, or an add-on board for the regulation?
I'm just back from a 6-week vacation, and will probably be ordering parts for building the prototype new SR-45 amp in the next week or so - I already have the chassis plates on hand.
It's a complete amp.
The problems I have with the older design are mostly that it gets too hot - the heat sinking is inadequate and there were no cooling vents in the original chassis plate. In addition, I have always felt that the hum and fluctuations from unregulated AC filaments and heaters is inconsistent with the sonic potential of the high-voltage circuit. So the new design has much larger heat sinks, a large vent, and an actual cooling airflow design, plus regulated filament voltages, high-voltage delay, and a relay to protect the output transformer from magnetization by turn-on transients. It's more of a no-holds-barred design philosophy than I have used in other products.
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Welcome back Paul!
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Paul, very cool that you're doing an "all-out" design! You're such a master at getting the most out of the "thriftier" designs, and I'm sure this will be something special. Your mention of heat reminds me of all the items used by gamers on their motherboards. I'm thumbless and too old for games, but I bought a motherboard from the wall at Fry's some years ago because it had copper radiators and copper tubing that work on a convection method. The salesman kept telling me I didn't need it for my computer use, but I couldn't pass up the hot-rod looks. Maybe some shiny cooling tubes that look like the old street-rod headers would look cool coming out the sides, or some coming out of the top that look like velocity stacks? I'm sure yours will be more elegant than that!
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Some mods to my SR45's:
A larger heat sink thanks to fellow Bottlehead forum member Jim R.
Replaced the electrolytic capacitors in the power supply with film capacitors. Still not sure how I made every thing fit :)
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi284.photobucket.com%2Falbums%2Fll38%2Fdebk3141%2F25c5c09b-a7fb-4286-a06b-420645b4a52d.jpg&hash=6f35077773d13c707e378831cd04f8f4a71ef018) (http://s284.photobucket.com/user/debk3141/media/25c5c09b-a7fb-4286-a06b-420645b4a52d.jpg.html)
Debra
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Cathode bypass still electrolitic?.
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Yes not sure how I would fit anything else there
Debra
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So if I were to parallel a small film capacitor with the 100uf cathode bypass what value would you use?
Is 1% or the bypass cap or 1uf too low? There really is not much room for a largish capacitor.
Deb
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Hi Deb,
I'd eeven try 0.1uF as a bypass., but have you tried the amp with no cathode bypass cap at all?
What does the manual call for here -- I don't have mine handy -- it may be that a smaller cap than the specified value could be used. I know my amp has no cathode bypass at all but it was configured as a tweeter amp and as soon as my new speakers get here I plan to experiment with some different values and types here.
Glad the heatsinks got to you ok.
-- Jim
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Like Jim says, try some. Just get out the jumpers and see if you like the sound.
Since it is the cathode it sees lower voltage. So a 100V cap is fine.
BTW, is this a Paramour or Paramour II chassis? It is getting full.
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It's been my understanding (and I may be wrong) that the cathode bypass cap, switching from electrolytic to film, will have a larger effect on the sound vs. a PS cap in a Parafeed design.
The cathode bypass cap is not a high voltage rating but finding a large valued cap in a lower voltage is a little painful. I'm using the new Panasonic EZPE series in my next project. They are cheap and look to be a little smaller than those.
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Aaron,
The power supply and cathode bypass cap are both in the signal path. But those cathode bypass caps are large values. Harder to find a good substitute.
To Deb and Aaron. Look at the last post in this thread. I am upgrading everything except the power supply caps. They are already 47uF@650V PP/Oil caps.
http://www.bottlehead.com/smf/index.php/topic,3303.new.html#new
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What is the effect of removing the cathode bypass capacitor?
How low a value can be used? The schematic calls for 100uf
Deb
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Doesn't the PF design significantly minimize the effect of the PS cap on the sound, effectively shifting the effect of the last PS cap to the PF cap? For that reason I'm sticking with lytics in the PS and the sheer size of the caps.
In my build I focused on the PS ripple instead of the make up of the cap and with a CLC dropped it from 0.1V to around 0.4mV in sims.
http://www.bottlehead.com/smf/index.php/topic,4953.0.html
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take this with a large grain of salt- based on a foggy memory 10yrs old- but I think I went with a large good-quality electrolytic for cathode bypass in my Paramours. 350or 450uF, or something like that. I think I calculated at the time that this effectively took it out of the circuit, because it never really got enough of a charge to activate it, but it served as a "holding tank" or a spring for the charges that did come in, but they dissipated inside it.
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In the midband (i.e. where the plate choke impedance is large relative to the tube's plate resistance) and with the output transformer connected to the cathode, the power supply and cathode bypass caps are out of the signal current loop. However, the choke impedance is no longer large in the deep bass, so some signal current does flow through the two caps. For this reason, the cathode bypass cap does improve the deep bass response - but is not necessary in a tweeter amp, and is also optional if the plate choke is really huge.
For example - 45 plate resistance is 1700 ohms. With a mu of 3.5 and a cathode resistor of 1500 ohms, the plate resistance of the tube plus unbypassed cap is (if I remember the formula right) 5450, or 3.2 times the resistance with a bypassed resistor. So if a 40-henry choke is used with the capacitor, then you'd get the same bass extension with a 128 henry plate choke and unbypassed resistor.
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I did an experiment and paralleled the 100uf cathode bypass capacitor with a 0.68uf Auricap. I picked the value because I happened to have a couple of them sitting around.
I didn't like it at all. The sound sounded smeared, especially with vocals. Was the paralleled capacitor causing a phase issue?
I removed 0.68uf and the sound was much better with the same material playing.
Interesting experiment, I don't know if the results would be the same with different value parallel capacitors.
On one hand I am very happy with the sound of the amps as they are now, but on the other hand it is a lot of fun and educational to experiment.
Deb
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I an not using a cathode bypass cap, My speakers are not the last word in deep bass...John
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Will removing the cathode bypass capacitor cause a decrease in gain?
Deb
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I was told years and years ago that the cathode bypass cap adds gain.
I believe this is because it changes the audio path to ground. Bottlehead hasn't used a cathode bypass cap in any of the Foreplay preamps nor the Seduction and Eros (and probably not Reduction). I think there might be one in the Quickie. Might not. I'm not as familiar with it.
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In the midband (i.e. where the plate choke impedance is large relative to the tube's plate resistance) and with the output transformer connected to the cathode, the power supply and cathode bypass caps are out of the signal current loop. However, the choke impedance is no longer large in the deep bass, so some signal current does flow through the two caps. For this reason, the cathode bypass cap does improve the deep bass response - but is not necessary in a tweeter amp, and is also optional if the plate choke is really huge.
So PJ, a similar line of thought and a question. I plan on using a pair of 300b amps for 80Hz and up (drivers have little below 70 Hz). 5k OPT primary, 1500 Ohm cathode resistor, 80 H plate choke. Can I get away without a bypass capacitor and have quality bass that low?
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I bent the leads into little "J" hooks and was hot swapping a 100uf cap in and out and no there was no apparent reduction of gain...John
Of course I could not recommend this ;)...John
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Last time i did that It was with the parafeed cap. The HT arced into my hand and i enjoyed 400+ volts. Ugliest "audio" experience.
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I bent the leads into little "J" hooks and was hot swapping a 100uf cap in and out and no there was no apparent reduction of gain...John
Of course I could not recommend this ;)...John
What differences in the sound did you hear
Deb
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I mostly use Hornshoppe Horns, they only go down to 60-70hz or so, then I go to a pair of subs. So I can't say about the deepest bass but all in all I think the upper end is a bit better without them...John
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One last suggestion. Try a well broken in KK Teflon cap as a cathode bypass, bypass. Still just use jumpers. I have done this in my Paramours and my Ack! dAck!. Those stayed in.
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I bypassed the 220uf cathode cap with a 2.2uf K75, (mylar, oiled paper,aluminum foil), in my Paramour 45's, EXO-45, BCP-15's. They are staying in. The bypass removed a level of grain and grunge that just made the amps cleaner with truer timbre.
Hard to imagine a bypass quality cap, in this application, making the sonic's worse.
Of course, YMMV...
Cheers,
Geary
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One last suggestion. Try a well broken in KK Teflon cap as a cathode bypass, bypass. Still just use jumpers. I have done this in my Paramours and my Ack! dAck!. Those stayed in.
What value do you suggest? I have KK teflons in 0.47uf
Today I put in a 1uf Mundorf silver/oil cap as a bypass. I keep putting it in a and out of the circuit. Not a huge difference, but it sounds a little smoother with it in.
Thanks
Deb
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Deb,
The 0.47uF KK Teflon is big enough. I would get by with 0.1uF or 0.22uF.
How many hours does the KK Teflon have on it? If less than 100 it would sound bad by itself. If less than 400 it isn't completely broken in.
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The KK teflons have about 300 hours on them.
I will get some 0.22uf and try them. They are big suckers, not easy to fit in with everything else I haev in there
Deb
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...
So PJ, a similar line of thought and a question. I plan on using a pair of 300b amps for 80Hz and up (drivers have little below 70 Hz). 5k OPT primary, 1500 Ohm cathode resistor, 80 H plate choke. Can I get away without a bypass capacitor and have quality bass that low?
"get away with"? sure. But that's quantity bass!
"quality bass"? there is no substitute for trying it and listening.
Seriously - I can't see a predicted level difference that would matter, but there will be phase differences and other more subtle effects (i.e. those that are hard to measure but easy to hear - there are uncountably many of those!).
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I go to this thread from time to time. Is there any hope of a regulated power supply for the parmour anytime soon.
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I go to this thread from time to time. Is there any hope of a regulated power supply for the parmour anytime soon.
Which Paramour?
Which power supply?
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Paramour is a legacy product. We will not be releasing any more upgrades for it.
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Paul, The paramour 2 and I would like to have main power supply regulated. Or, is it possible to put the soft start paramount kit on the 12at7? I suspect this would be major work. But I was wondering. But Doc I was reading in this thread the possibility of a board being avail. on a limited basis w/0 a manual,or am I mistaken.Jann
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The paramour 2 and I would like to have main power supply regulated. Or, is it possible to put the soft start paramount kit on the 12at7?
Why? and why?
The soft-start is technology implemented to stabilize direct coupling, which the Paramour does not employ.
Main power supply regulation and 2A3 operation is not possible on the PT-2.
While you "could" install the soft-start upgrade into the Paramour II, there are no instructions for this, and any installation errors will be your sole responsibility to troubleshoot.
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@najo49 -
What we have been using for regulated high-voltage power is a shunt regulation scheme. This requires both more voltage and more current from the power supply, as well as adding the regulator circuit. That's the reason why the old SR45 uses a 45 - the tube itself needs less voltage and less current than a 2A3, thus the Paramour power supply could power a shunt-regulated 45. It also explains why you can't easily convert a 2A3 amp to regulated operation.
Because I am not happy with the design of the original SR45, I have asked Doc B to not sell anymore of the boards. Instead (as described in various places in this long, rambling thread!) I am working on an SR45 design done right. When we have a working prototype, I'll start a new thread.
The Paramour II, however, does have enough power supply headroom to run a shunt-regulated driver stage (with unregulated output stage). The easiest way to do this is to use the Paramount soft-start upgrade kit. There are no explicit instructions available, but the conversion is similar to that for the Paramount. You must use the (included) 5670 tube instead of the 12AT7.
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If you just want a kind of dumb soft-start, it might be possible to implement using an Inrush Current Limiter in the incoming mains power. Note that this will somewhat slowly ramp all power, filaments and B+ alike - not sure that's what you're after.
See the linked datasheet for more info. I've used the CL-90 variety in kits for small push-pull tube amps, typically in the return leg from power trans primary to neutral (w/ hot switched upstream of power trans primary).
http://www.mouser.com/ds/2/168/920-325D-LR-245176.pdf
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I use cl 90 in all of my amps.
Right now I'm building a pair of Paramours and I'll be using the driver boards from my Paramounts that were replaced by the soft start ones.
Someday I hope Paul's new sr45 are released ad kits and I will build three pairs.
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Well, if I'm doing something that Xavier is doing..well..I'll keep doing it.
Garcon! CL-90's, all the way around!
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output transformer question-i am finally getting around to building the SR45-i am laying out on posterboard my wiring diagram-this concerns the MQ exo45 output transformers-there are 4 wires 2 on either side-i pair is red and blue and the other pair is black and clear--the red and blue read .436k-and the black and clear read 1 ohm-so the red and blue go to my outputs -i will guess that red is positive -how may i ck this to be sure--and on the black and clear wires one wire goes to the plate via the coupling cap the other to the junction of the hum pot, cathode bypass cap and cathode resistor-does it matter which wire goes where?
thanks howie
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Usually with Mike's iron, red and blue are your primaries. The black and clear will be your output side.
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Here is the exo-45 hookup data
http://www.audioasylum.com/forums/magnequest/messages/4679.html
Michael
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ok so the side with the large resistance is the primary side-the exo45 is handwritten--but there are no dots-on the primary side both red and blue come out of the transformer at the same distance from the coil--on the output side one wire obviously comes from the inner part of the coil-i will post on the mq site thanks--howie
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The dots are used on lug connections. You have flying leads.
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aaron -thanks-i should know these things by now-i still am not certain what lead goes where-i suspect that the red to the plate and blue to ground and clear to positive and black to neg-being they are 550 for the pair i would like to be certain-i am surprised how much real estate i need for this-output transformer,large plate choke, triad power choke,grid choke and output trannie times 2 -i am using jensen radial style caps which are large -a mundorf m-lytic cathode bypass cap-again times 2 -plus all the other things needed-rt now it is all layed out on 1 piece of poster board-i am not sure whether it will be 1 amp or 2--this is my first scratch build-so it is fun but i am a little nervous-if put on one chassis are there any special cautions between the left and rt sections-
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It's best to ask MQ questions in the MQ forum or email Mike directly if you are not sure.
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My mnemonic is the "blue plate special" - an old diner term that has stuck in my head. Blue to the plate (i.e. high AC signal voltage). For series feed transformers the red goes to the high voltage supply; for parallel feed it goes to AC ground; in this circuit that would be the cathode. There is a parafeed cap in one of these lines of course! Note that whether the red lead goes to B+ or to ground, the important thing is that it has near zero AC signal voltage.
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Paul,
From what I know of transformers it will work either way but swap absolute phase on the output.
However, wiring it as it should be yields lower noise.
Is that right?
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I don't know all the reasons for choosing a polarity, but I'm pretty sure there are more than one.
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ahhh!!-Paul--the blue plate special it is!!-mike got back to me and the blue goes to the plate and red to ac ground-and black is ground on the secondary-and here is a little read on the blue plate special
http://en.wikipedia.org/wiki/Blue-plate_special
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Howard,
Now Paul should reveal what BPC stands for.
He has before, it isn't a secret but it is funny and appropriate.
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You mean the Brainiac Plate Choke? I wish Mikey would make a run of them.
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YUP!
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi244.photobucket.com%2Falbums%2Fgg7%2FGrainger49%2FSmiles%2Fcongrats.gif&hash=8537e933ba501766e863d5aabbaca0ebcaf2719f)
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Haha! I acquired that nickname back in the old VALVE days when I would work out operating points in my head. I don't think anybody has used it in the last 10 years though. :^)
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Nowadays we call Peej "I'llbebackwithananswerafterathoroughanalysisiac", and the products have improved vastly because of it. But it's kind of a crappy name for a choke.
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well!-it being a choke it is a form of audio-erotica
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ok bad puns put aside-i have just breadboarded my power supply for the SR45--i have 121v ac in
334v ac out and my dc voltage is 454v dc---the schematic shows 300v ac and rectified voltage at 372v dc--how concerned should i be at this point-- with nothing else in circuit--thanks howie
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From what you have described it sounds like you have no load on your circuit. If that is the case then your voltages are about what you should expect. You can approximate the load using a high wattage resistor of appropriate value; you'll have to figure that out yourself since I don't know how much current your circuit draws.
Robert Lees
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robert -thank you-that is correct no load--howie
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Robert, The resistors should be two 10w ,10ohm ww in parallel thats a 5 ohm load and they will never overheat.
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If you are testing the high voltage supply with a resister you need 6000 ohms and at least 25 watts.
Michael
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now my next question--i am using the paramount softstart which is for a a 5670 tube - i am using a 6cm7-so there is a pinout difference for starters--using the softstart schematic and comparing that to the sr45 schematic -on section 1 of the 5670 on the softstart-pin 4 is plate-pin3 is grid and pin2 is cathode-the connection to the board are as follows-OB to plate -rca input to grid via 220r -KregA to cathode-so my connections on section1 of the 6cm7 will be OB to pin 6 which is the plate-rca to pin7 the grid and KregA to pin3 the cathode- and the same thoughts to section 2 --is this correct-here are links to 5670 and 6cm7
http://www.classiccmp.org/rtellason/tubedata/6CM7.PDF
http://www.mif.pg.gda.pl/homepages/frank/sheets/093/5/5670.pdf
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6K and 25 watts sounds right ;D When you say 5 ohm 20 watt you are undoubtedly thinking of a dummy load for the output transformer :o
Robert Lees
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As long as you are aware that the 6CM7 has two very different triodes, you should be OK. Triode 2 is the beefcake that regulates the power supply, and triode 1 is the driver triode for the 45.
I'd use a much, much larger heatsink on the "top" MJE5731 than comes with the Paramount soft start.
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--as for the larger heatsink ,what size --a link would be best if you have one- i actually did not get one with my softstart kit-is there another tube that would be optimal--thanks howie
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could i use the 5670 with the SR45?
No.
as for the larger heatsink ,what size --a link would be best if you have one
There were some supplied with the SR-45 kit, though I don't have the part number handy.
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here is a link to digikey-stocked heatsinks
http://www.digikey.com/product-search/en?pv623=6&FV=fff40012%2Cfff80068%2Cfffc003b%2C1880002%2C5940002&mnonly=0&newproducts=0&ColumnSort=0&page=1&stock=1&quantity=0&ptm=0&fid=0&pageSize=25
having never chosen a heatsink before slightly mystified-the hs300 looks to be the best choice
ii would need 1 each total 4 -howie
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Deb,
The 0.47uF KK Teflon is big enough. I would get by with 0.1uF or 0.22uF.
How many hours does the KK Teflon have on it? If less than 100 it would sound bad by itself. If less than 400 it isn't completely broken in.
Found a bypass capacitor I really like!
I put in a 0.1uf Obbligato Teflon Tin foil capacitor. They are not quite broken in yet but even new they sounded great. Liked them enough that I soldered them in this morning.
Smoothed out any rough edges left and not quite sure how to describe it but the amp sounds "faster" music just seems to flow.
Deb
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Ya, I bought a few of those caps just to try them. I put a pair of .47 in my eros phono and I was really surprised to see how good they sounded. very poor mans v cap!
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The good heat sinks are large, like 1x2x2 inches, extruded aluminum not bent sheet aluminum. They are too large to fit on the "soft-start" board.
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Hi Paul. How about an update on the project sir? :)
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i am getting close to finishing the SR45-am just about to put the soft start boards on-these come with a string of diodes 1n5373B -why this particular diode vs a 4007-i have put some sf4007 in place-- as i was getting ready to solder a little bell went off-i will wait for a answer--here are some pics --the main chassis plate will sandwich between the chassis box and the top-similar to the transformer cover-the transformer cover will sit right on the top not up off the top - as the pics show
https://picasaweb.google.com/100635555508988591604/Sr4502?authkey=Gv1sRgCLTk_5qar63CYA#5960746136821081762
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Hey howie,
Good you asked -- those need to be the supplied zeners, not just basic diodes. You probably saved yourself a good boom!
-- Jim
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You do some beautiful woodworking! Please post picks of the finished amp!
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jim thanks-i googled the 5373 a very robust diode--aaron thank you--i wll post a soon as i am finished-which may be postponed --i ordered some 249k resistors for the rca input to ground resistor-they came and i hung them on the wall till i needed them --they are 249R-not 249K
-so that makes me ask how critical is that 249k resistance-i can get close to 249k paralleling something or other-2 475k gives me 237.5 k and so on
since i live on a island-i can't access things like the rest of the world-there is a radio shack here -it caters to cellphones and tv/vcr's etc--
thanks howie
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Paul, how are the new amps coming along?
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i am waiting for 2 resistors that were mis-ordered-while i wait i am cking my connections etc-my question is what goes to b- what does not-i have yet to put the slowstart board on as i need to get in there for the resistors i am waiting for-when i put the slowstart bd on 1 wire goes to b- from the board-i have b- from the bottom of the cathode bypasscap--where else do i need to pickup b- ----the places in question are coming from the rca input to a 249k resistor then to b- and/or ground -and at the bottom of the zener diode string-meaning at the other end away from where OA connects with the plate of section 2 of the 6cm7---; the diode string connects to ground do i also pick
up b- -----my star ground will be at the corner of the power trannie --many thanks howie
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Paul, how are the new amps coming along?
Sorry I missed this when it was posted.
I got stalled the last few months - partly holidays and other obligations, partly the two power supply circuit boards. But as of this afternoon I have a complete draft of the most intimidating one - sixteen diodes, eight electrolytics, one regulator circuit, two time delay circuits, and two relays on a 9x2.25" board. And two dozen off-board connections. It's pretty crowded...
Right now the plan is to do the second board (basically three more regulators and two C4S's), refine them both, and build a couple prototypes.
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Thank you for the update Paul. :)
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Aaron, I have to thank you for keeping my nose to the grindstone.
When I first got into this it was through attending VALVE club meetings. Dan - Doc B - always started the meeting by going around the room asking what we had done the last month. The peer pressure kept us all innovating and trying things - it was a really exciting time for us all! Your periodic reminders have the same effect. So thanks!
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Alright my friend, another month has past! Any updates sir?
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Sorry, been a slow month with some as-yet-unclear medical problems. I did get most of that second board done, and decided that the final version will likely combine the two boards to make more efficient use of space. Thinking I'll then be able to put in some film caps for the last PSU and the cathode bypass.
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Monthly check in time. How's the progress sir?
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Picked up some parts at Bottlehead HQ on Wednesday, to mock up the power supply.
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Super excited about this amp Paul! Its fun to see the progress updates! Taran
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THIS is the Bottlehead amp I have been waiting for!
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Paul, forgive me but are these going to be mono blocks or a stereo amp? I can't remember which way you decided..
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Because of the extensive new circuitry, the chassis plate is 10 by 16 inches for a monoblock - somehow I think a 16 by 20 inch chassis would be a little clumsy!
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And there's not enough room for my tl 404s!
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Music to my ears, literally and figuratively!
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What's the word Paul, how goes the build?
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Hi Paul, how goes the project?
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PJ came over to the island this week to pick up a bunch of parts. I believe they were mostly for power supply testing (big resistors to simulate the load, etc.), but output iron and a sizeable chunk of wire was picked up as well. It is my understanding that the power supply is being built on the chassis rather than breadboarded, so the amp must be starting to look like an amp!
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PJ came over to the island this week to pick up a bunch of parts. . . .
I hadn't realized before that PJ wasn't local.
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Semi-local - door-to-door is about 90 minutes, longer in the summer when the ferries are full of tourists.
Josh's description is accurate. I need to put the fully loaded PSU output on the scope to know which regulator chips I can use for the filaments, and to know how much current I can take out without overheating the PT-7. Then I can finish the second large PC board, which has all the heat sinks.
I had hoped to do all that without using the full chassis, but there are so many wires with high voltage or current it just looked like a disaster waiting to happen, so I'm doing it the slow but clean way. Not really my natural style; there's a reason Doc doesn't usually let me build stuff by myself :^)
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Tha K's for the update and keep one hand on your pocket ;)
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Hi PJ. Thanks for all the updates on the SR45 amp project--we appreciate it!
A quick question--have you and Doc decided for sure whether this amp will be an actual BH product?
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Hi PJ. Thanks for all the updates on the SR45 amp project--we appreciate it!
A quick question--have you and Doc decided for sure whether this amp will be an actual BH product?
We have not talked strategy at all.
But I expect it will follow some non-traditional path, like crowdfunding or limited production run. Like the DAC, it's not cheap and will appeal to a smaller audience than our more mainstream products. I can see a semi-kit also - the main PC board will be pretty large (for Bottlehead) and has an awful lot of components on it, which will make debugging through the forum a challenge. Dynaco did this back in the day.
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Appreciate the info. Thanks!
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Hi Paul, how's the build coming? Any updates?
BTW, this thread has been on going for two years now :)
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Back-ordered parts (from March or so!) finally came in a couple weeks ago.
Yeah, it's going slow - I keep getting distracted with other designs, most of which have not yet come to the point where we want to say anything about them.
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Hi Paul, any updates? Dan really doesn't want to bring those other products to market. What could be better than a new SR 45 amp ;)
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We will be shooting manuals for two to three new products this month alone.
PJ's commitment to a strong, reliable implementation of the SR-45 is unwavering, and since the scope of this project is beyond any kit offerings we currently have, there is no real prior precedent for how long such a project will take to complete.
-PB
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You are correct PB, but I can poke the bear once per month :). You guys are amazing and I'm thankful for what you bring to the world. Nothing here but a dedicated fan base reinforcing a desire for the ultimate design.
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We will be shooting manuals for two to three new products this month alone.
You let the cat out of the bag there :o
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You let the cat out of the bag there :o
That's the boss's job, not mine ;)
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Hi PJ, how's the build coming along?
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Thanks for the ping, Aaron!
Seductor has been taking up a lot of my time, but progress is being made. More later.
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How about that update sir? :)
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One more try this month; any updates Paul or are other projects keeping you bogged down?
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Other projects - mostly getting my late mother's estate through probate right now. Long story, but coming to a close finally.
There's a lot of developments going on at Bottlehead, and the SR amps are related to those developments, so they are not orphans even if it seems like it right now.
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I'm looking forward to these new developments!
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Anything new PJ?
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Monthly poke to see if this project is still in the queue, anything new PJ?
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I was just contacted by the person who acquired the SR45 amps I used in my own system. He is trimming down his collection and is offering them up for sale. I don't have any other specific info, so ping me if you would like to get in touch with him and I will give you the contact info.
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Thanks for the post, Dan!
The amps have been sold.
-- Jim