I just moved to a new apartment, and finally managed to reconnect all those pesky cables and wires in my AV setup. When I turned it on, tho, I got a loud hum emanating from my main speakers (I haven't yet set up my surrounds, so I dunno if they would've hummed too), which was independent of the actual volume on the receiver. This hum only seems to go away when I unplug the cable connecting my subwoofer to my receiver. The subwoofer is about two feet from the left main speaker, which is about the same relative position it had in my old place, and I didn't encounter this problem at all there. What's going on??? All help is appreciated.