After seeing Gabe's excellent 2A3 amp project with its promise for good performance it started me wondering if a 6550 or Kt88 could be substituted with a few modifications to work in the same circuit. Since I have extra KT88's and 6550's now and none of the 2A3's would this work? Any thoughts here would be appreciated.
Joe
Joe
Hi Joe;
I think it's an excellent idea! FWIW Angela.com has posted a set of schematics for an EL34 SET that was based on the JE Labs 2A3 - so why not? As far as the use of a shared cathode resistor for the 2 channels, that's pretty widely used in some circles to good effect - IIRC the Decware Zen used it as did some console hifis from the good old days.
Of course you'll have to get some iron that can handle the extra 3.2 amps of heater draw at 6.3V.
A parting thought is that the use of a cathode follower between the voltage gain and the current gain sounds fine to me in my little 2A3 - so why shouldn't it rock in a KT88? I bet it'd really be able to drive some loads that my 2A3 can't.....
All the best and good luck!
Morse
I think it's an excellent idea! FWIW Angela.com has posted a set of schematics for an EL34 SET that was based on the JE Labs 2A3 - so why not? As far as the use of a shared cathode resistor for the 2 channels, that's pretty widely used in some circles to good effect - IIRC the Decware Zen used it as did some console hifis from the good old days.
Of course you'll have to get some iron that can handle the extra 3.2 amps of heater draw at 6.3V.
A parting thought is that the use of a cathode follower between the voltage gain and the current gain sounds fine to me in my little 2A3 - so why shouldn't it rock in a KT88? I bet it'd really be able to drive some loads that my 2A3 can't.....
All the best and good luck!
Morse
I am working on my dream amp and it will be using 6550s.
I am still in the design stages but I am paying particular attention to the power supply.
I got hooked on the 6550s when I refirbished a McIntosch MC-60 for a friend. I liked the sound of that amp when i finished with it not to mention the test I ran on it. The noise floor was around -83 db down from the clipping point which was about 90 watts out. The frequency response was good: dead on @ 16 hz, dead on @ 25 Khz. The output never varried more than 0.2 DB The worst case distortion was 16 hz @ 90 watts out (.30%). 16 hz is the bottom range of my audio generator.
I know that that McIntosch cheated some with the MC series amp. It does employ some negative feedback.
I did trash the 5U4s because I noted much less low frequency distortion with the silicon diodes.
There is much more I could tell you about this amp if you are interested.
I am still in the design stages but I am paying particular attention to the power supply.
I got hooked on the 6550s when I refirbished a McIntosch MC-60 for a friend. I liked the sound of that amp when i finished with it not to mention the test I ran on it. The noise floor was around -83 db down from the clipping point which was about 90 watts out. The frequency response was good: dead on @ 16 hz, dead on @ 25 Khz. The output never varried more than 0.2 DB The worst case distortion was 16 hz @ 90 watts out (.30%). 16 hz is the bottom range of my audio generator.
I know that that McIntosch cheated some with the MC series amp. It does employ some negative feedback.
I did trash the 5U4s because I noted much less low frequency distortion with the silicon diodes.
There is much more I could tell you about this amp if you are interested.
Please don't anyone misunderstand me as I am not putting down Gabe's amp in any way. I found it very interesting as all Gabe's amps are. I just thought it would be fun to put together a 6550 or Kt88 SE amp because for one thing the tubes are cheaper and I just plain like the sound. Well, I'm cheap also.
This is Franks fault ! Well I couldn't take the blame myself.
If anyone has any ideas or schematics they would like to share please throw them in.
Thanks
Joe
This is Franks fault ! Well I couldn't take the blame myself.
If anyone has any ideas or schematics they would like to share please throw them in.
Thanks
Joe
Hi Joe;
>>Please don't anyone misunderstand me as I am not putting down Gabe's amp in any way...I just thought it would be fun to put together a 6550 or Kt88 SE amp....<<
No misunderstanding over here - FWIW, you're very close to a contingency plan of mine (should the stocks of affordable 2A3's and 6SL7's ever dry up), which is to convert my beloved 2A3 over to use EL34's and 12AX7's. It looks good on paper anyway!
You might also take a look at ASL's MG15: http://www.divertech.com/mgsi15dt.html for proof that the concept is sound. I bet you can get yours running for a lot less $$ though!
Good luck and all the best,
Morse
>>Please don't anyone misunderstand me as I am not putting down Gabe's amp in any way...I just thought it would be fun to put together a 6550 or Kt88 SE amp....<<
No misunderstanding over here - FWIW, you're very close to a contingency plan of mine (should the stocks of affordable 2A3's and 6SL7's ever dry up), which is to convert my beloved 2A3 over to use EL34's and 12AX7's. It looks good on paper anyway!
You might also take a look at ASL's MG15: http://www.divertech.com/mgsi15dt.html for proof that the concept is sound. I bet you can get yours running for a lot less $$ though!
Good luck and all the best,
Morse
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