John:
... I am now back to using the supply without the regulator... because it's an extra level of UN-needed complications.
So I just put back the 120 ohm resistor and a 470uf - 250v cap.
Works.. nice enough.

The 13FD7s take 40 V - 45 V negative bias. Not going to happen with a 25.2 V transformer unless you double it. But then I don't have a 25.2 V trannie and it would take 3 x with the 12.6 V transformer, but then I wouldn't have -200 for the long tail on the phase inverter.

Taking it off the 182 VAC (reverse 240) trannie gets me the -200 V and lets the 12.6 V center tap be tied to ground for balanced heaters.

Right with you Peter. Thanks for the very detailed CCS theory. It's an ingenious circuit.

Earlier today, actually Saturday late, I turned on the 5902. Hooked up the ipod to listen to some of Peters sweet classical music.
I sat back and kinda dozed off. I woke to an unusual sound in the speakers. The bass sounded like a ping instead of a boom.
So I moved over to listen more closely, and the sound was just weird. I was thinking, wow, something is wrong. I heard a low rumble
in both speakers. I turned down the volume on the ipod, and still the rumble. I was just about to start talking my second language,
Sailor talk, when my wife noticed that the plug into the ipod was not fully seated. She pushed it in and, all back to normal.
Just plain and simple sweet sounds. Thanks again Peter.
This new amp build wont weigh 45 ------ pounds, and wont cost thousands, and will probably sound just as good.

Tonight I modified my breadboard to add some octal sockets so that I could also test this amp with 6V6GT tubes.

It worked out alright. I can either plug in the 6AQ5 or the 6V6 ... one set at a time.

I don't know if it's psychological or what... but I get the immediate feeling that the 6V6 "seem" to offer more bass.

Anyway... I thought I'd post an image of this beauty ... just as it looks now on the bench in ALL its glory:

Nice work Peter. Looks like a labor of love. My wife was looking at your bread boarding for the kitchen sink. I appreciate your work.
Let me know about your chassy layout. I can do both.
I am just getting a parts list for this amp, for Mouser. I think the dropper cap is a good deal on ebay.
Thinking about the box or chassis. It must have some bling.

Looking more at your test setup Peter.
Learning so much by seeing your technique.
Thanks again....

Hi peter.
Just going over the power supply schematic. I noticed you left out the surge resistor in the filament circuit.
Should I use it or not?
I am excited to get the whole amp schematic using the 6v6. I need to get the parts ordered.
I am just finishing the test speakers. Thinking about ordering the best Edcors you suggested.
Thanks Peter. I really like the spread out bench circuit you presented.

I have decided on this OPT.
https://www.edcorusa.com/cxpp25-ms-8k
Seems like a good deal. I like the multi taps for speakers. Also the 20-20K FR. And the 25 amp rating.
Not that I have compatible speakers, or a capable amp.

For the 14K in the PS, use four 56K's at 2 watts each.
Must be more solutions, Peter?

Or, three 40 K's for 13.3 ohms.

Perhaps that's watts not amps?
25 amps will power your dishwasher, toaster and the microwave plus more.

Each Op-275 draws 5ma... (10ma) ..and the 40v Zener requires a couple milliamps to keep it in conduction:
So...
Anything from 13k to 15k will work.
We have to drop the B+ (235) down to 40v. So we need a resistor to drop 195v.
(195v/ 13,000 = 15ma)
13k allows 15ma through to feed the two Op-275 @ 5ma each (10ma) and the other 5ma will be taken up by the 40v Zener.
(195v/ 15,000 = 13ma)
and 15k allows 13ma through which is 10ma for the the two Op275 and 3-ma left for the 40v Zener.

Either way works.

Great.
Found these on ebay. Could use three of them for 13K at 6 watts.


http://www.ebay.com/itm/39000-ohm-39K-2 ... 41841997e1

John:
Here's the box I'm going to use... but I bought it 2009 at Michaels and the one they now carry may be a bit smaller:


So ..here's a link to a box similar to the one I'm going to use.
It's a little larger .. but you will be using larger OTs... right?
http://www.amazon.com/Wooden-Blank-Box- ... d+book+box

Here's the sockets I bought:
http://www.ebay.com/itm/4X-8pin-Bakelit ... 7675.l2557

I don't think it's psychological, I noticed the same thing back in the 60's. Even though they claim the 6AQ5 is "equivalent" to the 6V6 within it's maximum ratings, 6V6's often do sound better in the same circuit. They may be just different enough to make it worthwhile using them.

Thanks Mr D:
I haven't had a chance yet to really do a decent comparison... but it was just an instant reaction.

But I am building this new amp with octal sockets for 6v6gt as well as 7-pin sockets to accept the 6AQ5 as well.

And ... for max flexibility:
...esp since power for these filaments is so easy using a 10uf NP dropper cap (in series 25.2v@ 450ma).... I will also add a 5uf NP dropper on an A/B switch so I can easily opt to use the much less costly 12v6gts as well (50v@.225a)

There are also a bunch of other 6V6 "equivalents" if you want to get into 9 pin or Loktal sockets. The 12AB5, 6CM6, 12CM6, 7C5, 14C5 are just a few. There is also a 19AQ5, but you'll probably never see one.

Thank you...

I have this box. Was going to use it for the 5902 amp, but changed my mind.
Still thinking about a metal chassis with some wood end plates.
I like the opt's on top with the tubes. I don't know....