[Sander deWaal]

Eeyore said:


Right now, I'm obsessed with getting good sound that lasts out of an
amplifier that intends on blowing its fuses every few hours.
All semis are OK, genuine types, no Chinese fakes.

Very frustrating, apparently it suddenly bursts out into oscillation
after some "trigger" frequency comes along.
Without input signal, it stays OK for days.

I now have a memory scope and a sweep generator attached to it,
trying to initiate the effect. No luck so far.


You have a marginal stability problem. Try tweaking the output Zobel.
The only other way is to fix the feedback loop.



Zobel was OK, I found out someone forgot to put in the cap between
base and collector of the predriver.
As you probably know, this C sets the dominant HF pole of the voltage
amplifier.

Thanks, you Chinese *******s for letting me search for 2 hours ;-)

--
"Due knot trussed yore spell chequer two fined awl miss steaks."