my new harmon kardon avr is making a humming noise all the time. it isnt coming from the speakers and seems to be localised to the amp, this is a new avr 630. do most peoples amps hum ? Any ideas how to solve the problem or am i just being too sensitive to my new system. i have never had a seperates amp before . would i be better getting a less powerful amp - would i get less hum from a less powerful amp ? could it be a problem with the transformer ? also the amp keeps turning its self off after varying levels of time. i have tried unplugging all the speakers this hasnt helped.