Well, the positive feedback input could add to instability, and I don't quite see the need of a tip42c gain booster ahead of triple tip42c outputs, when you've got mje340/350 as drivers.
Still building an amp out of 2n5401/5551 + Mje340/350 + TIP42c should be doable. These are things I can actually buy instead of all these exotic 2sc/2sa stuff which would mostly be counterfeit in the US market.
SOA on real mje340/350 looks like 300 ma @ 50v and 250 ma @70v. SOA on TIP41c looks about .7 A @ 50v with a gain minimum of 30 at .3 amp. So each output pair draws .02 A at maximum output soa current, so you might be able to drive 10 parallel pairs output just with a MJE340/350 driver. That would give you 7 amps out @ +-50 v which would be some useful wattage. More wattage short term ("music power") but not more than 7 amps for house music or low peak music.
Look at this thread
http://www.diyaudio.com/forums/soli...across-emitter-quasi-complimentary-stage.html
which is a **** simple amp worked out in both single supply and split supply versions . I'd say just parallel the outputs, and forget all those exotic BC*** transistors which Europeans are so fond of.
I've got a schematic on a 200W amp from the 80's which is just sort of this arrangment, with 2 pairs output 2n3772 instead of one.
Note to jumpers in, mrclock lives in South Africa where he can buy counterfeit transistors of any marking he wants, but hardly anything real. I'm familiar with trying to push things into Mexico, a lot of stock gets changed at the border unless both parties are somebody important to the customs guys.
BTW I have a single 80 v supply in the amp I'm upgrading, and no room for the circuitry in post 15. Thanks anyway. I used up the regulator board space to put in 5 parallel TIP142's to regulate down to 72 v at 7 amps continuous.