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In Reply to: RE: Hey Tre! posted by tube wrangler on June 27, 2012 at 20:01:41
Here's my original post, and yes I was coached by both J and D as the project was made. And yes, there's what I'll call micro differences, some of which "may" have been improvements....
http://db.audioasylum.com/mhtml/m.html?forum=tubediy&n=153234&highlight=Satan+patiently&search_url=%2Fcgi%2Fsearch.mpl%3Fforum%3Dtubediy%26searchtext%3DSatan%2Bpatiently
I had not "yet" tried multiple by-pass caps, because I didn't have any at the time. I did however make an effort to minimize wire, see the pictures (much less than what Dennis does, I've seen the underside of his amp BTW).
I also had a much lower DCR power trans than Dennis uses, whatever that's worth, and I used dual 5R4GY's instead of one 5U4GB, which Jeff should like. I had custom made filament transformers with a tab for a CT that the R and Ck directly soldered to, from there to ground, (no wire).
Yes the voltage on the 2A3 was a little bit higher than what was "recommended", I didn't think that could "ruin" anything as the 2A3 was still operating UNDER max dissipation. I tore the amps apart 2 years ago or more. Before I did, I changed the driver to a CCS loaded lo mu triode,
instantly cleaner, better. I also changed the PS to "normal" which made other noise go away, but we now know that the original PS was "no good".
Jeff later felt happy to thrash my build, yet thankfully admits having misadvised.
See:
http://db.audioasylum.com/mhtml/m.html?forum=set&n=69636&highlight=grant+handley&r=&search_url=%2Fcgi%2Fsearch.mpl%3Fforum%3Dset%26searchtext%3Dgrant%2Bhandley
Follow Ups:
Hello GSH,You relied primarily upon me, and I was NOT correct in values and voltages in several areas, as my understanding of the circuit was not as good back then, as it would be today.
We both should disclose the fact that I told you to make the AC cord (ONLY) out of inexpensive Carol 300 VDC or 600 VDC 12 AWG wiring, and the audio out of TCSS and silver wire.
The TCSS never got installed. You wired the amp mostly with the inexpensive 12 AWG Carol, which has a "big wire" (very negative) thick and out-of-time sound to it.
Use of huge Carol 12 AWG hook up wire, in places other than the AC cord, guaranteed poor sound IMHO.
I also had the B+ supply filtering and shunt regulators mis-done, totally my fault back then, as far as obtaining low ripple. I made the same error with Slownlo, and even my own implementations in 2008-09.
You also never sent me a finished schematic of what you made, so that I could comment on voltages, and various obvious errors I would have spotted. IMHO, we BOTH made errors back then.
That a CCS improved things is not surprising at all to me, it was a band aid for numerous implementation and circuit errors. You gave up on the project, before fully informing me of exactly what you built and allowing me to suggest corrections. About two years later, in 2010, I told you quite precisely in what three areas that amp was "boogered", and it certainly was.
Its a shame you have never heard one of Dennis 2A3 amps, to know what performance level is possible. I have, that is what keeps me active.
Live and learn.
Cheers,
Jeff Medwin
Edits: 06/28/12
"The TCSS never got installed. You wired the amp mostly with the inexpensive 12 AWG Carol, which has a "big wire" (very negative) thick and out-of-time sound to it."
Yes, true BUT: the Carol 12g wire was only to the rectifier (yellow and red), and the ground (less than 6" total in one uncut piece from the HV CT
to the input, through the cap terminals. There's no other wire in the circuit, period, except for the lead to the OPT which was paralleled with silver wire. BTW we both know Dennis uses the stock red and yellow leads out of the stock Hammond power transformer to his 5U4GB. That sure isn't TCSS. So, the ONLY real wire "flaw" is the 6" ground, that actually only counts from C2 to the input, which is less than 3".
So the 3" ground wire of heavy copper, was "bad". OK
The difference in the op points is NOT large, as stated, still UNDER max dissipation for the 2A3, and the 7B4 was "close". I don't see how this could dramatically change anything. I don't think the small voltage differences could be "heard", in fact, they could easily blur between "perfect" and what you would call "way off" just with the line voltage changing. So I veto that.
The missing multiple by-pass caps is the largest "flaw" and I admitted that from the word go (see original post)
I also got tired of the hum and installed a Bourns pot, which fixed that.
I'm not really trying to defend or prove anything, just state the what is.
I do believe that the paralleled caps (if done whatever right is) could be an area of improvement for ANY CIRCUIT, which is why I brought it up in my other recent post. I give Dennis direct credit for having pursued this, although I don't have any direct experience with "what exactly" he has done, other than note that he said "it's expensive, and will cost more than the sum of the rest of the parts". With that, it's hard to get moving, expensively, into darkness, to maybe achieve light.
Furthermore, I think a direct coupled SE amp is a good sounding thing.
Perfecting it, is just an interesting set of possibilities.
I and many others may not prefer the 7B4-2A3 to what I or those others are preferring now, but overall improvements in PS, wire and caps are still valid for other circuits, so whatever real findings Dennis can show,
can likely "help" other designs in these areas. I wish this "tone" could be upheld in this discussion.
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