How are you grounding your stuff? In my experience with chipamps, star grounding is the best solution. I had a ton of hum in my LM3886 before I grounded that way, it was going through the chassis for input and output signal causing a ton of hum. Then I re-did it again because I had run wires near all the AC->DC power board and tranny causing hum lol, but just keep your signal wires away from power wires as much as possible, then ground everything at one point. I actually soldered mine together at one point.