I have the same problem except all my speakers have a slight hum to them and its been that way since day one I just assumed it had something to do with my wire management. Apparently it hasn't bothered me that much because I still haven't taken the time to narrow it down, havn't had the time. When I was just running a Denon receiver to the speakers I never had any noise in my speakers. When I ordered the 990/7700 combo I even made sure to purchase balanced cables so I didn't have any noise and low and behold, I do. The hum is way more noticable when using analog interconnects. I read somewhere on this forum that there was a slight chance the 990 could have a bad chip in it which was really rare but I just don't want to go any length of time without my 990. Maybe this weekend I'll be able to narrow down the problem. Oh yeah, I'm also using dedicated 20 amp receptables.