Bottlehead Forum
Bottlehead Kits => Legacy Kit Products => Paramount => Topic started by: debk on June 14, 2012, 09:20:53 AM
-
I know there has been multiple threads on the parafeed capacitor value, and I have read them. I just ordered the paramount , and I just want to make sure I have this correct.
I already have a 300b amp so I am going to build the Paramounts for 2a3 tubes from the get go.
From what I understand the kit comes with a 3.3uf parafeed capacitor. From what i have read the ideal value for a 2a3 paramount with the standard iron is around 5.6uf to 6.8uf. With the MQ iron using the Paramour plate choke (BH-6 or BCP-15) the ideal value is around 10uf.
I plan on upgrading to the MQ iron after I have had some time to listen to it with the standard iron.
So since decent capacitors in this size are fairly expensive, would I be ok just building it to start with with the included capacitor, and then upgrading to he 10uf when I upgrade the iron? Or should I just start with a 10uf capacitor or would you suggest something else entirely?
Also I have read that you should not use the Mundorf silver/oil in the 2a3 paramount because of the heat produced. Is this really an issue with the 2a3 version? Would it alos be an issue with the Silver-gold/oil capacitors? I have not had much luck finding the operating temperature specs for these mundorfs.
Thanks for any help
Debra
-
Debra,
I know that there has been mention about a possible issue using the Mundorf silver/oild caps, but have been using them in my amp for over 4 years with no problem.
-
Debra,
The standard capacitor will give you a good response. In realistic rooms you won't hear a difference in bass response between the 3.3uF and 6.8uF. If your speakers are flat at 20 Hz or 40 Hz it takes a long room to give you that deep a response.
I bought the BCP-15 and TFA 2004 (Sr) for use in my 2A3 Paramours. I went with the incredibly cheap 10uF Obbligato black Film in Oil caps. I haven't upgraded in 5 years. The 10uF value was needed with the MQ iron I bought to get equivalent response to the stock cap and iron.
-
http://www.soniccraft.com/mundorf_silver_oil.htm
deb here you are --the operating temp is 131 degrees fahrenheit
-
Thanks,
Is 55 degrees C adequate for the 2a3 Paramount?
Deb
-
I'm out of town (in Virginia) for 10 days and don't have all my resources handy. But if you find the Cornell-Dubilier web site they have some extensive information on various capacitors, including the effect of heat on lifespan. Bottom line, there is no such thing as a magic temperature marking the boundary between exploding and living forever... cooler is always better.
For what it's worth the 2A3 direct coupled version dissipates much more heat from the cathode resistors, because the cathode is at 260 volts.
Capacitor value: my estimate for the best value is 2*L/R squared - L being inductance and R the transformer primary impedance. At this value, the impedance presented to the tube drops slightly (2/3 the midrange value? Sorry I don't have my simulations at hand) in the deep bass, then rises as the capacitor dominates at lower frequencies. Note that some Japanese audiophiles use much larger capacitances. Even the largest cap will perform much like a series feed arrangement; one of the parafeed virtues is a more resistive, higher impedance load presented to the tube at the lowest frequencies.
A smaller capacitance raises the cutoff frequency (roughly as the square root of the capacitance), but provides the tube with a safer minimum load. Somewhere around half the nominal capacitance the load never drops below the midrange value. In general I think this is a good compromise for using the 45 because it keeps the distortion low at maximum power. Smaller than that, you lose bass extension without getting any benefit in return.
Conversely, a larger capacitance will deepen the bass extension for small signals, at the price of possible distortion with large low-frequency signals. Since I run 101dB speakers with 300Bs, I use a 6uF cap in my Paramounts - I'm not likely to run out of steam. Around twice the nominal value, the load impedance benefits become small relative to a regular series feed.
Keep in mind that this assumes a perfect power supply, and a speaker impedance that is a pure 8 ohm resistor. There will be some interaction with both impedances, so the generalizations above should be taken with a grain of salt. I recommend experimentation with the target speakers in the target room - listen for bass distortion and extension. Once you know what capacitance works best, then you can spend some bucks on higher quality caps to get cleaner treble. I'd get a ~6uF cap, and parallel the 3.3 to get 10uF - gives you three values to listen to.
Well, not the answer you were hoping for, but food for thought. So much of engineering is not answers so much as the art of compromise...
-
Paul
Thanks for an excellent explanations. It is certainly an answer that makes sense and a great plan of attack for the problem.
I appreciate it
Debra
-
Deb,
Thank you for starting this very helpful thread. Because of it, I picked up a pair of used Mundorf Silver in Oil 5.6 uF caps to try out. I've been very happy with the Mundorf SIO caps in my Stereomour.
Best,
John
-
Thanks John
I oo have used Mundorf in a number of my builds, and have been very impressed.
Please let us know how they sound and hold up.
I am thinking of trying the Clarity Cap MR. I hear they sound very good and have a higher temperature rating
Deb
-
Hey John - Used Mundorf silver/oils sounds like a good way to go. Where did you get them, and how was the condition? I would like to use all silver/oils in my speakers. Now I just have my ampohm's bypassed with small silver/oils. One thing I can say is the addition of the silver/oils really smoothed things out. I also used the silver/oils in the Quickie.
-
Deb, I'll definitely post my thoughts, such as they are, on the Mundorf SIO caps. Those Clarity MR caps look good...excellent comments by those who have tried them and a 100 degree C. temperature rating.
Earwaxxer, I found them on AudioCircle...I think they were used in a speaker crossover. They are pretty good with reasonable long leads still. They tested at 5.690 and 5.705. There are still some 15 uF caps left if that helps. I found they smoothed out my Stereomour very much, too. I'm a big fan of the SIOs...
Best,
John
-
After having lived with the MR caps in my Quickie and Sex amp I have to warn all of you that they're extremely revealing. They brought a huge leap in separation and clarity at first. I have over 300 hours on them now and they really haven't changed much. They could be a little rough in the first 100 hours but have smoothed out since. Still, they hold nothing back and cannot be considered warm at all. Sometimes they remind me of the sound of Krell gear: cool and clean but not as forgiving as I would like.
I previously used Clarity ESA caps which are much more forgiving and a bit warmer in the upper treble. The ESA are still very good with detail but lose a lot of depth and ambiance compared to the MR caps. If the the MR caps rate a 10 in clarity then the ESA come to about a 6-7. I'm thinking of going back to the ESA just to see if I like them better. It's hard to give up the extremely clean and clear sound of the MR caps but sometimes they are so revealing they make listening to some of my favorite recordings unbearable.
I may also try the Jupiter and Mundorf caps for a warmer flavor.
-
Hey Rob - Interesting observations with the Clarity MR's. Seems pretty consistent with other reviews. I think thats why I tended to error on the side of the oilers. It would be interesting how an MR would sound bypassed with a small oil like a Mundorf SIO, or GSIO.
Cheers - Eric
-
That's an interesting idea.
How about a small teflon for the bypass
What value would you use for the bypass capacitor?
I have a pair of 0.22uf Vcap TFTF sitting around.
Debra
-
Debra,
0.22uF would be fine for a bypass. I often use 0.1uF regardless of the cap value being bypassed.
-
Debra - I would be curious how the v-cap sounds as a bypass cap! I have been curious about them. Tres expensive!
-
I have the Mundorf silver/oil caps in my Paramount's, but never thought to add a bypass cap to them. I have a pair of Russian Teflon 0.1uF caps that I could try. I think that I will start burning them in.
-
Hey Brad - Not sure you would gain anything bypassing such a good cap. I think the general consensus is to only bypass when you really cant afford to upgrade the cap in question. Bypassing is a double edged sword. The caps have to play well together. The Mundorf silver/oils IMO have all the desirable characteristics of the best caps (clean, but organic, good soundstage, lack of glare, good separation of instruments, low noise) . Adding a teflon may sterilize things a bit. Make it a bit too clean. If your system is already a bit too organic and tubie, that could be a good thing. Curious to hear how it works in your system though.
-
So is the consensus that he Mundorf silver/oil is ok with the 2a3 Paramount?
Don't want to spend the money on them is they will have a problem with the heat
Debra
-
I just looked at the Mundorf site. The Silver/Oil are rated for 55
-
Sorry that the discussion got more general without getting specific first!
I do not recommend any component rated for less than 85 degrees C, inside any of our amps (except of course the Quickie!).
That's because I am a moderately cautious engineer by trade, of course - I have not attempted to measure the temperature directly inside any of the cases, mostly because it will be so dependent on the circulation (inside and out), ambient air temperature, and power line voltage. Empirically, we have not seen failures with parts rated 85C or greater. We have seen failures of for example the original Jupiter beeswax caps in the S.E.X. amp - I can't remember but I think they may have been rated 50C? (Jupiter has since revised their construction, and we have added ventilation slots to that amp.) We've seen failures in C4S installations, so I've revised my design rules - many products now have heat sinks and/or use larger transistors.
For what it's worth, in the case of power transformers and semiconductors, I normally design for a nominal internal temperature of 100C, while the parts we use are rated for 150C. For the semiconductors I assume the under-chassis temperature is 60C - but I haven't verified that.
Also for what it's worth, the effective environmental temperature is usually around a 50/50 mix of sir temperature and radiation temperature averaged over the usual 4-pi steradians. If a part is close to a power resistor (for instance) it can see some high radiation temperatures!
-
Thanks Paul, having been a cautious engineer at one time I understand you reasoning.
So the Mundorfs are a no go. I may give the Clarity Cap MR a try, or take Grainger's suggestion and go with the Obligatto oil cap. I wonder how the Obligatto would sound bypassed by the Vcap teflons I have siting around
Debra
-
For what it's worth, I have never liked bypassing a larger coupling cap with a smaller one. The resulting sound often seems smeared. I might consider bypassing an inexpensive high capacitance 'lytic in a power supply, but what is the point of buying a boutique cap if you have to bypass it with a boutique cap?
-
Hi Debra,
Have you tried the Russia K40? Paper in oil. May not be as starkly truthful as the Teflons, but very easy on the ear.
And still cheep...John
-
Thanks Paul, having been a cautious engineer at one time I understand you reasoning.
So the Mundorfs are a no go. I may give the Clarity Cap MR a try, or take Grainger's suggestion and go with the Obligatto oil cap. I wonder how the Obligatto would sound bypassed by the Vcap teflons I have siting around
Debra
Debra,
Can't hurt to try. The Ack! dAck! offers a "Teflon output option." It is a 0.1uF bypassing the stock Auricap. So it is done, and results vary.
-
I do not recommend any component rated for less than 85 degrees C, inside any of our amps (except of course the Quickie!).
For what it's worth, in the case of power transformers and semiconductors, I normally design for a nominal internal temperature of 100C, while the parts we use are rated for 150C. For the semiconductors I assume the under-chassis temperature is 60C - but I haven't verified that.
Thanks, Paul, this is very helpful
What I am wondering is that several of us are using "underrated" (for heat) boutique caps in our amps with great success and over a long period of time (I've been using Mundorf S/O in my Stereomour for a year, for example. I believe others have even used Jupiter caps, perhaps). Given your statement about design temps, I should remove my Mundorfs. This is unlikely to occur, however, because they sound great!
So what can we do to cool the interior? I'm thinking a lot more airflow, perhaps even forced? I don't want to get too complicated but surely there is a nice 12v DC fan that could be added in some reasonable manner to increase airflow. I really want to try the Mundorfs in the Paramounts without too much worry.
Best,
John
-
I have Mundorf SIO in my Eros, it is up on spikes increasing ventilation. I have the same caps in my FP 2 and the base doesn't even have feet on it. I'll probably put spikes on it too after Paul's post.
I liked the recent picture of a custom Bottlehead product, can't remember which, with a grill at the back of the base and a fan that snuggles up to the grill to increase cooling. Using a 12V fan on a 9V or 6V supply will decrease the speed, lower the CFM rating and make it very quiet.
Edit: Found the pictures.
http://www.bottlehead.com/smf/index.php/topic,3046.0.html
-
I do not recommend any component rated for less than 85 degrees C, inside any of our amps (except of course the Quickie!).
For what it's worth, in the case of power transformers and semiconductors, I normally design for a nominal internal temperature of 100C, while the parts we use are rated for 150C. For the semiconductors I assume the under-chassis temperature is 60C - but I haven't verified that.
Thanks, Paul, this is very helpful
What I am wondering is that several of us are using "underrated" (for heat) boutique caps in our amps with great success and over a long period of time (I've been using Mundorf S/O in my Stereomour for a year, for example. I believe others have even used Jupiter caps, perhaps). Given your statement about design temps, I should remove my Mundorfs. This is unlikely to occur, however, because they sound great!
So what can we do to cool the interior? I'm thinking a lot more airflow, perhaps even forced? I don't want to get too complicated but surely there is a nice 12v DC fan that could be added in some reasonable manner to increase airflow. I really want to try the Mundorfs in the Paramounts without too much worry.
Best,
John
Reading my note again, I may not have been very clear. I meant that the temperature of the wire inside the transformer, and the temperature of the silicon chip inside the transistor, would be kept below 100C. Inside the chassis the air temp is of course much lower - hotter than room temperature, cooler than 100C.
We have been adding ventilation slots in the chassis plates, gradually, as products get revised. This allows thermally-driven airflow, taking it in below the wood base frame and exhausting through the slots.
Cooling air from a fan or other cause does not need to flow very fast, but it does need to flow over the heat sources and then out of the chassis. Components don't sweat, so a fan inside the closed chassis won't cool anything - you need that cross ventilation!
-
I have Mundorf SIO in my Eros, it is up on spikes increasing ventilation. I have the same caps in my FP 2 and the base doesn't even have feet on it. I'll probably put spikes on it too after Paul's post.
I liked the recent picture of a custom Bottlehead product, can't remember which, with a grill at the back of the base and a fan that snuggles up to the grill to increase cooling. Using a 12V fan on a 9V or 6V supply will decrease the speed, lower the CFM rating and make it very quiet.
Edit: Found the pictures.
http://www.bottlehead.com/smf/index.php/topic,3046.0.html
Granger - nice build! - 'those pretzels are making me thirsty!' - sorry - couldnt resist the Seinfeld quote!
-
Hello Debra,
I've found this site http://humblehomemadehifi.com/ (http://humblehomemadehifi.com/) to be most helpful in describing specific qualities of various capacitors. There are also useful recommendations on bypass caps. I hope this helps.
John
-
Thanks john, I have actually seen that site before. A lot of information.
I think what I may do is build the 2a3 paramount with the stock capacitor, and then put a temperature probe next to the capacitor and see what I measures
Debra
-
Eric,
I can't take credit, it isn't mine. But isn't that gorgeous wood? I really like that finish on the Oak.
Debra,
Try bypassing with two pair of jumpers. It took me quite a few swaps the first time I did it. I decided to leave the KK Teflons in my Ack! dAck!
-
Reading my note again, I may not have been very clear. I meant that the temperature of the wire inside the transformer, and the temperature of the silicon chip inside the transistor, would be kept below 100C. Inside the chassis the air temp is of course much lower - hotter than room temperature, cooler than 100C.
We have been adding ventilation slots in the chassis plates, gradually, as products get revised. This allows thermally-driven airflow, taking it in below the wood base frame and exhausting through the slots.
Cooling air from a fan or other cause does not need to flow very fast, but it does need to flow over the heat sources and then out of the chassis. Components don't sweat, so a fan inside the closed chassis won't cool anything - you need that cross ventilation!
Thank you, Paul. Adding additional vent holes in the right spots and/or adding a small, slow fan (such as running a silent 12v DC fan at 6v) to create greater cross ventilation is the goal, then. If ambient is around 25C and max temp is 100C, and cap max is 55C, then it should be possible to get there, perhaps. I just love my Mundorfs....
Best,
John
-
Well a couple of things. First, I've drilled a few vent holes above where the parafeed cap are located. I drilled six 7/32" holes. Since I'm painting the top plates, I think they will simply disappear to a great degree. I'm also planning on using Herbie's Tenderfoot 1/2" feet which should allow a lot of air to get in underneath the amps. Each of these is done with the hope that this well allow better crossflow ventilation.
Also, I realize I picked up a set of Mundorf Supremes, not the SIO (and paid appropriately and with full and proper disclosure by the seller...just misspeaking on this thread). So I'm going to get a new set of SIO for the cap and will probably allow them to hang a bit low where they can get good air flow around them.
Best,
John
-
So I thought about this some more and added a few more holes above the parafeed capacitor (9 total). I also added some holes around where the cathode resistors mount (7 total), figuring this was where Paul said there was a significant source of heat. I have painted with black lacquer with a clear lacquer top coat. I'm not the best craftsman around...the flaws are obvious...but I'm happy with the result and think the extra vent holes will keep the air flowing better. Oh, and I decided to get the 3.9uf Mundorf SIO...I bi-amp and am not worried about bass extension.
Best,
John
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fwww.hawthorneaudio.us%2Fforums%2Fdownload%2Ffile.php%3Fid%3D1552%26amp%3Bmode%3Dview&hash=0a355d269021248e09f8ae1085137d82c60c4b2b)
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fwww.hawthorneaudio.us%2Fforums%2Fdownload%2Ffile.php%3Fid%3D1553%26amp%3Bmode%3Dview&hash=fee77f17caf2c829bc19f82915861a7cea2f1fbd)
-
One last post for this thread...here are the Mundorf 3.9uF Silver In Oil caps installed with a bit of an air gap to allow free flow of air to the extra vent holes above. Remember, heat rises (which is down in the photo).
Best,
John
-
As an update to this thread, the hottest place I measured on the surface of my Paramounts was 56 degrees C. with most areas within 1/2 inch away being 53 degrees C or lower. Underneath, the cathode resistors are at 80 degrees C. The Mundorf SIO are measuring at 43 degrees C. maximum (they are rated at 55 degrees C max).
Remember, I mounted mine "low" and have extra vent holes drilled. While I would like to see more than 10 degrees from max, I'm not too worried. I'd love to see what others are measuring in their Paramounts, particularly if they are mounting the caps "high" and didn't add additional vent holes.
Best,
John
-
Those Mundorfs are a thing of beauty! Just proves it... 'cap lust' is real, although tubes are always going to be prettier.
-
Newbie question.
I will be replacing the Solen 3.3 Para Feed caps. I have Mundorf silver in oil and have a couple of questions.
Do I need to bleed off the Solen's before un-soldering them? If so, what's the best way to handle this.
Any advice on safely performing this task is appreciated.
Thanks.
-
Any advice on safely performing this task is appreciated.
Thanks.
Simply use your voltmeter to measure across the cap and see if it has any voltage. If it does, connect a 10K ohm resistor across the leads to drain it off. You will be able to see the voltage drain off on the meter.
-
Thanks Doc.
I'm assuming DC voltage is what I am measuring?
-
Yes, DC. Once it gets below 10 or so volts you should be fine.
-
The Mundorf Silver in oil do not appear to have polarity.
Do you know if they do, or will either orientation work?
Thanks again for all your help.
-
nope - dont have to worry about polarity with any film cap, unlike electrolytics. Some say that there is a inner winding side and an outerwinding side and its good to go from inner to outer. Not sure that makes a difference.
-
I installed the Mundorf caps. and all went well. No voltage detected on the old caps. so no need to drain them.
Thanks for everybody's help on this.
-
Just stick your tongue on it. If there's voltage you get a nice sensation, or more. If not, no harm done.