Like many people I had a hum coming from my sub. I'm connected to the low level input and I'd tried everything suggested, different cables, different power source etc. Then the other night I decided to have another play to try to sort it out. The problem in the end was that the high level in volume was set to max, when I turned this down to min all humming disappeared. Quite obvious really! Also I don't get the initial thud when I switch on now. Was this documented in the manual? Has it been in this forum before? Ash.