I had the same problem with my video side causing hum.
I put a passive filter between the video side, going into my main AV processor, then into the main amp.
The passive filter takes RCA's in and out, and it's called a "buzz off", by ROLLS. You can find them in Guitar Center or other music stores, guitarists use them to cut down hum.
It works well in stabilizing my system, as I run my video side into the audio side, through my Quad amp, for surround sound.