Originally Posted by Michael Koster
Funny you bring this up. I'm building a hybrid consisting of a SET stage with a true current boosting push-pull output stage.
The main ideas are:
Current is shared between the output stage and the SET stage by a ratio of 20:1 by virtue of the 20:1 ratio between R6 and R4,R5. This reflects the 250R OPT primary impedance back to the triode node at R1,R17 as 5K ohms.
The triode actually sees 10K plate load due to the 50/50 current sharing of the anti-triode Q5.
The output stage operates in class AB.
The idea is that the amp behaves just like a 20W SET into the real loudspeaker load, based on reflecting a constant % of the load current back to the triode plate while the output voltage nearly exactly follows the triode plate voltage.
Well, I was asking for a much more elementary reason. I'm building my first pp power amplifier - a transformer input differential circuit using video pentodes (cuz I got 'em) direct coupled to 2A3s . The drivers are loaded with Wavebourn's SVCS (The strange looking icons with ccs discs and the sine wave between) and the cathode circuit is like the cap coupled one that Shoog used on his EL84 amp.
I don't really understand them yet but I've always been interested in what you guys have been doing with the anti-triode and when I saw your schematic and realized I was assembling most of the parts anyway I thought it might be easy enough to get the op-amps and try it out somewhere along the way.
The idea of getting a single ended signature with one tube @ twice the power is appealing when thinking of tubes like the 45 or 10, but I haven't seen much in the way of subjective comments from people who have actually built and listened to them.