Sorry, you wrote the question correctly, I misunderstood.
No amplifier should produce an audible buzz through the speakers.
If you have no input signal and the volume is set to max you may hear a very faint hiss (and I do mean very faint) right next to the speaker, never a buzz or anything else audible at 10 feet.
Since this particular one physically vibrated and had a problem you heard out of the speakers it was a dud.
What other gear do you have?
Oddly enough if you have an AVR that is high enough up the food chain to have pre-outs 99.9% of the time external amps are not needed.