Unplug all the input from your amplifier,if the buzz or loud hum still there,you might have a problem with its power supply..look for deformed high valued (usually valued at 1000 uF or more)capacitors their top is flat not rounded.If you find one or two replace them,it should correct the problem,good luck ! P.S. Also toggle the top of the capacitors they should not turn loose or else their wire terminal is corroded .

If the space permits use Engineer PZ-58 Screw Pliers its great at unscrewing ruined screws