THis is a dusie and I read the thread below about hum. I got my 7700 yesterday and simply swapped it for the 755. So I removed the 755 and hooked up the 7700 with same exact connections and NOW I HAVE HUM. No hum with 755. Hum with 7700.

I called Steve at outlaw. He suggested the usual things, those that are described in the manual and have been talked about here. Got started late last nite and gave up (tired). I don't understand why I should have a ground loop hum now when I didn't before, and everything is connected identically. Audio and speaker wires not running parallel or near the AC. Two dedicated 20 AMP new circuits wired in for my 755 setup worked well. Also a third that was already there in the living room.

And yes: I tested the circuits with on of those yellow testers, indicating proper connections, neutral, hot, ground etc. And yes I disconnected the dishnetwork power plug and coax feeds. Even disconnected the phone line from the dish receiver.

Very frustrating. I think I need to start from scratch and "re-build" the system.

Oh yes: Steve said that "differential amps" (of which the 7700 is one) are different from 755.
What does that mean? Thanks guys.