It seems to me that the original concern was someone else thinking that an amplifier was bad. Do we all agree that it is usually very easy to cause a very loud hum at the speakers of a working amp, without a whole lot of effort at a mic input? Just thinking it's easier to show that an amp is working than that a mic is not. Joe
Quite true Joe, how about just making up a simple oscillator (tone source) to prove that the amp is in fact working?.
