Audio Amplifier Distortion Tracing
 

Hi all,

I'm using an old (1960 I guess) Advance AF generator (15hz-50khz) in
an attempt to discover what kind of distortion my Technics hifi
amplifier is producing so I can fix it. However, for some reason I'm
getting terrible self-oscillation from the otherwise stable (though
not-very-nice-sounding) amp that can't be stopped once it starts. I'm
just wondering if I should be using some sort of buffer between the
generator and the amp input? At the moment I'm just feeing it direct.
It's the only cause I can think of. I've checked the generator by
itself on a suitable scope and it's absolutely rock solid right across
the range and the attenuators are fine so it can't be the gennie
itself; must be something I'm doing wrong. What doesn't help much is
the gennie doesn't state what its output impedance is. Not sure if
that's relevant or not, though.
Any suggestions?
cheers, cd