I hve this problem with my subwoofer humming whe reciever is turned off. After changing recievers, but same subwoofer and cables, i get this humming from my sub when i turn my reciever off, humming also stops when disconnect LFE cable. could i have a bad reciever? I also have a wireless blu-ray player put in at time i replaced reciever. Sub has two prong power cord so it caint be ground loop. original sub cable, so i know thats not bad. any ideas?