Using mains transformer as output transformer

[kenpeter]

I run the description through my head backwards and sideways,
the lightbulb inside must be missing the pullchain or something.
I know I'm going to regret this, but could you draw it?

[smoking-amp]

"could you draw it?"

No problemo. Seems an obvious solution to me, someone may have already mentioned something similar. I think Anatloyi (Wavebourn) mentioned such a self regulating CCS for something.

The two drive signals are scaled so that the tail voltage AC variation is nulled to a minimum.

[smoking-amp]

CFB version. The drive signals can be adjusted for a minimum AC null on the tail again. Or maybe just leave Q1 with a steady bias on its gate, could be good enough. Just trying to keep audio out of the CCS tail's slow regulation (no resonance then). The slow regulation is for compensating non-linearity in the tube, causing growth of current on large signal bursts.

Since the audio doesn't go thru the cap, the RC low pass can be set to be lower than the L (OT primary) and C resonance, avoiding resonant activation by enveloping, I think.

[kenpeter]

And now for something completely different:

Anyone remember what engineer this this crossed
bias balance was named for? I've seen it mentioned
here before, recently too, I'm sure of it... But I draw
a blank what name to search for...

Maybe those bypass caps at the bottom should have
been moved up and used as coupling caps from grid
stoppers to the driver(s) instead... My bad.

[Michael Koster]

Ding!

It's Alan Dowter Blumlein, Ken

[smoking-amp]

Alan Blumlein

how many bonus points do I get?

edit:
Darn, Michael beat me to it!


Looks like the AC signal will be going thru that cross coupling cap though. Resonance?

[kenpeter]

Serious bypass goofup fixed...

As for a resonance? I suppose it probably has one...
I don't see any reason it would be within the audio
passband. Does it cause DC balance to oscillate?
Would that mode ever have a gain approaching 1?
Are you suggesting its a motorboat of some sort?

[smoking-amp]

How about just getting rid of the transformer altogether. More problems than its worth. Now we get a SET emulation without triode or transformer. Probably works better than SET. Q2 would be a constant Beta part. Uses complementary current outputs. Maybe needs some extra resistance in the Q1 source lead.

[smoking-amp]

Fixed


On the Blumlein scheme, I wouldn't think it would be any more problem than parafeed. Just have to be careful where the resonance falls so it doesn't get excited. Can probably make it a damped resonance as well. But if it can be gotten rid of ..... one less artifact.

[kenpeter]

Yeah, that works. The screen sees RL, and damn what the plate sees.
Within a pentode, plate don't much affect audio processing decisions.

Its kind of odd the screen can pull both up and down, is there some
screwball variant of the anti-triode at work in the output totem?