Bottlehead Forum
Bottlehead Kits => Kaiju Stereo 300B amp => Topic started by: drewh1 on December 25, 2015, 09:53:51 AM
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Happy Holidays Bottleheads!
I have a heavily modded Stereomour and Crack, Now I want to build the Kaiju! As I already have built and modified a couple of kits without issue, I plan on starting with all the high end stuff, Mundorf silver/oil output caps, teflon tube sockets, Goldpoint Volume control, and some other special goodies. Which leads me to wonder about tubes. I have JJ 2a3's in my Stereomour and enjoy them. I have the following questions for you experts and then would like some opinions on the best tubes, (knowing no one has actually built this amp yet?)
1. Mesh plate vs solid plate - I have heard great things about true mesh plate tubes, seems the only 300b with real mesh is the EML.
2. Does changing the driver tube have more tonal impact than changing the output tubes?
what tube would you use (under $1000 a pair range, so I can't afford NOS)?
EML Mesh Plate
Sophia Princess
JJ 300b
Sophia Mesh Plate (I understand this is a solid plate with little holes in it)
Shuguang Treasure
I am leaning towards the EML mesh as they seem to be highly regarded by many as long as they are used with the soft start.
Thanks in advance and sorry for kicking a dead horse!
drew.
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Jac at EML advises accurate filament voltage, so I would get the regulated DC filament board if you get those tubes. He also advocates using a hum pot, which Kaiju has. I'd also go for a V-cap or other quality cap between the driver and the 300B (0.1uF/600v).
Sorry, I've done very few comparisons of 300Bs.
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Helpful information Paul - thanks. I am leaning towards the EML. Also thinking Mundorf silver/oil for the output caps.
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Hey Paul,
I noticed this information on another thread.
The other issue is that EML specifies +/-4% for filament voltage, but power line voltages can vary +/-10% (sometimes more outside the US). Never fear, we have ways to adjust that voltage if necessary. You might check your power line before you start the actual assembly.
My mains measure between 125 and 128 volts. About a 6% variation. Will this need to be regulated for the EML Mesh?
thanks,
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My mains measure between 125 and 128 volts. About a 6% variation. Will this need to be regulated for the EML Mesh?
thanks,
Like the Stereomour II, Kaiju has excess filament voltage which is dropped by series resistors to get the desired voltage. These resistors can be modified to deal with out-of-bounds power line voltage. The DC option is regulated so it needs no adjustment.
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got it! thanks again for your quick response.
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teflon tube sockets, Goldpoint Volume control,
I consider teflon tube sockets to generally be a significant downgrade from what we provide.
The controls on the Kaiju are for channel matching and are not volume controls, so I would also consider this modification to be a bit of a downgrade also.
-PB
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Ok, I'll take your input, and appreciate saving any money that isn't well spent - so besides output caps and tubes, and DC filament, are there any other places you might consider worth upgrading.
However, one of the reasons I want the Goldpoint is because I have a remote servo motor volume control, sort of a must have for me. So is not at all possible to use the goldpoint (even if it is a trade-off)?
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We have left considerable room for alternate parallel feed and interstage coupling capacitors. I wouldn't mess around with anything else.
A remote servo volume control would go well into a preamp...
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duh - I didn't do my homework!
Would a passive work? The Submissive?
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duh - I didn't do my homework!
Would a passive work? The Submissive?
It kind of depends on what you have, and to some degree what your sources are.
A passive control tends to have a lower input impedance, which can be a tougher load for your sources to drive, and also a higher output impedance than the average linestage would have. Do you have a link to what you'd like to use?
-PB
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Hi Paul - My source is an Ayre DAC with 2 v rms output. I do not need source switching as everything goes through the DAC via USB. In fact I never wired the switch in my Stereomour.
I know this seems like sacrilege but can't I incorporate a simple 100 k ohm volume control into the amp chassis between the inputs? That would be preferable to an external unit. Apologies if I am being dense . . .
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I know this seems like sacrilege but can't I incorporate a simple 100 k ohm volume control into the amp chassis between the inputs? That would be preferable to an external unit. Apologies if I am being dense . . .
The layout of the Kaiju makes this nearly impossible. You can put the control in its own box with a very short pair of cables to the Kaiju, that would work nicely, though it still depends a bit on the impedance of the control you have.
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100 k ohm (same as Stereomour)
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I would build that into a Smash or a BeePre. A 100K control isn't going to be that happy driving cables.
You may also be able to just use the volume control in your DAC, but YMMV.
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Hi Paul - BTW, I really appreciate you spending this much time on this issue. I am really trying to keep my system simple. unfortunately my DAC has been made with the same philosophy and does not have a volume control. I would prefer to build an external passive volume control since I do not need additional gain or source switching. If you could tell me the input impedance of the Kaiju, I'll figure out what I need to use and build it into a separate box. I can use my servo on any Goldpoint and can build one to match the necessary impedance. I am able to keep the interconnects very short so that shouldn't be a big issue.
thanks again for your time with this.
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Your DAC has a heroically low output impedance (something like 70 Ohms), and the Kaiju has 100K input impedance.
A passive control that was in the 10-15K range between the two should work well.
If you need long cabling anywhere in the chain, I would recommend having it between your DAC and whatever is feeding the DAC, which would allow for the DAC itself, level control, and amplifier all to be fairly close together.
-PB
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thanks Paul! I also may have found a solution that takes out any additional circuitry in the signal path. I can control the volume digitally with J-River. Should have no impact on quality at all. I have been playing with it with my Stereomour. I just have to find a convenient way to access it remotely. So I have options. Anyway, I am now super excited about building this amp and can't wait to start ordering (after the first of the year!)
Really glad you guys do what you do. Happy New Year.
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drewh1
I am using dual 10K mono Goldpoint ladder type attenuators between an Ayre QB9 and Paramount 300B amps (original version with 12at7) with no problems. Interconnects are 2 feet long from dac to attenuators and 3 feet from attenuators to amps.
Jim
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Great to know Jim - thanks. I am going to go with Goldpoint so I can attach my servo motor to it. I have my DAC and amp located next to each so I can get away with very short interconnects.
I am interested in the digital volume with J-River, but am reading conflicting reports about quality impacts. imagine that in the audiophile world :)
BTW, I just got the DSD upgrade. I had the old 96k version. It really is worth the money, takes the QB-9 DAC to a whole new level. Not a subtle improvement, and way cheaper than buying a new DAC. Highly recommend it.
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I am interested in the digital volume with J-River, but am reading conflicting reports about quality impacts. imagine that in the audiophile world
The only way you can resolve this is to try it for yourself. You get what you pay for when it comes to opinions on the internet.
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Ain't that the truth!
So I just put my order in. One more question.
Knowing I'll be using the EML Mesh Plates, I did not order tubes. I assume I will need to make sure the Filament Voltage and current are correct prior to using the tubes. Can I measure this without tubes, or will I need a cheap set of tubes to set things up?
thanks again, when does it ship? ;D (joking of course)
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drewh1
Have had the dsd upgrade for just over a year now. Use Cd's (44.1) ripped to external HD with mac mini running Pure Music and the difference/improvement is worthwhile to me. Must try some high rez PCM and dsd soon.
Jim
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It is amazing how well 44.1 sounds through this DAC. I keep going through my old CD rips and it is like hearing them for the first time. I have downloaded comparison DSD and 192 PCM files. I couldn't hear any audible differences. J-River (which I use) converts DSD to PCM anyway. Charlie Hanson prefers PCM so the DAC probably does a better job with it anyway!
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Knowing I'll be using the EML Mesh Plates, I did not order tubes. I assume I will need to make sure the Filament Voltage and current are correct prior to using the tubes. Can I measure this without tubes, or will I need a cheap set of tubes to set things up?
Provided the instructions are followed in the manual for measuring your AC line voltage and selecting the appropriate power transformer wiring, no additional testing is necessary.
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Got my kit! It includes the DC Regulated filament kit - Given that I will be using EML's from the start do you still recommend building the kit stock and then adding the DC circuit board? l
I won't have my tubes for a couple of weeks, so I could probably get everything done prior to the arrival of the tubes. I can't measure voltages before getting the tubes and would prefer to have the circuit in place prior to firing up the tubes.
thanks for the advice.
drew.
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Read p. 10 of the DC manual.
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Well, of course I did read that page. The reason I am asking is that Paul J. recommended that I utilize the DC Filament circuit for use with the EML's. So I am just making sure it is reasonable to start using the EML's safely with the AC then switch over.
I also need to modify the circuit after getting some measurements. So, I also imagine the measurements won't be accurate until I have the DC circuit in place.
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In the best of all worlds, I myself would use cheap, worn tubes until everything is running correctly and the filament voltages look perfect. I can do that, because we have plenty of tubes lying around. The only reason for such care is that the EMLs are really expensive, and I have a substantial portion of Scottish DNA. My grandfather used to say we were descended from the finest horse thieves in Scotland - also the reason my ancestor moved to America... :^)
But I'm assuming you don't have a spare pair of used 300Bs. So yeah, build it stock, take it slow and careful, and do all the tests. Be extra careful about the power transformer input voltage (starts on page 29). If there are any questions, this is the place to bring them up. We will be paying special attention to any confusion or problems, until there are a few successful builds.
A few hours at a slightly wrong filament voltage will not harm most tubes, but EML specifies a very tight +/-4% on the filament voltage, and conforming to that spec is important to retain their warranty.
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Just to give a little of our rationale here, what we can give competent tech support for is an amp assembled by the method we describe in the manual. Which is to say assemble it with the AC supply first, make sure it is functioning properly, and then install the DC upgrade. If the amp is built with the DC supply from the get-go, our tech support advice in the case of it not working is to tell the builder to complete the amp with the AC supply first, make sure it works right, and then install the DC supply. When part or assembly changes are made to a first run kit you will have to wear your pioneer hat.
(https://americanhistory.si.edu/sites/default/files/styles/large/public/Fess%20parker%20cap%20b.jpg?itok=zxO6ofxf)
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Thanks Doc and Paul - I am definitely taking this one slow and will be careful about the voltages through every step. When I get to putting the tubes in, I'll take all the measurements and check in with you Paul about any needed changes.
yeah, it would be great if I had a crap pair of 300b's to test with, like most of us, I am extravagant in some ways and really cheap in others. The kit looks great and I am really excited to be building it.
drew.
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So I just did the transformer power tests. My house circuit is right at 125. I wired it accordingly.
7 &8 - 199.7
11 & 14 - 6.74
12 & 13 - 6.74
I am a bit over the 5% on all of these. Just checkin, let me know if I should change something.
drew.
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That is a bit on the high side. It will drop a bit when the transformer is drawing full current, but probably not enough.
However, the EML mesh 300B draws 1.4 amps, greater than the 300B spec of 1.2 amps. This will pull the filament voltage down further than normal.
If you are lucky, these two effects will cancel each other. So I suggest you proceed with the stock build, and add an AC voltage measurement across the filament (socket pins 1 and 4) before proceeding with the other voltage measurements. If you still have a voltage outside the EML spec of 4.8 to 5.2vRMS, you can adjust the 0.51 ohm resistors to refine it. (See these resistors in the photo on page 35 of the manual.)
Incidentally, you may wish to mark the setting of the hum pot before installing the DC heater circuit. It will otherwise be difficult to determine the best setting.
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Great minds think alike! I was wondering if the additional voltage would bring it closer to spec.
BTW, I did manage to get my hands on a pair of 300bs to set up and test with, so I am good to go. I'll just keep checking in with details as things move along.
I really appreciate all your time and help Paul, but what are you doing working on a Saturday!
drew.