Hi Eugkim; unhook your amp from everything and plug it into the wall, if it hums it maybe a mechanical hum-- check to see if transformer is well secured. If it still hums it is probably DC "leakage" into your power lines-- nothing you can do about this except complain to power co. Next, plug amp back into your receiver-- you'll know if this is the source of the hum-- it's probably a feedback loop between amp and pre-amp. Try "floating the ground" between amp and receiver by using a two prong cheater plug-- not really recommended, but often used to reduce ground loop hum. Also try same with your receiver. If when all this is hooked up and your speakers hum, there is something wrong with the amp (if the receiver is not connected), and something wrong with the receiver if it's in the chain. Just use a logical process of elimination to isolate the problem. Most likely it's a ground loop problem. Good Luck. Craig
