Guys - I'm having this problem too, but it happens regardless of input source. For the folks having the problem above, did it only happen when you were watching cable, or the ground problems with the cable affected all sources?
In my case, there is a hum from the sub (Earthquake 12") even when the rest of the system is off if I turn the sub on. I've tried fiddling with the power/sub cable and occasionally it seems to improve, but I can't isolate what I'm doing when it gets better. I figured maybe they just couldn't be crossed, but separating them totally doesn't seem to be the trick.
FYI, the sub wire goes from the AV rack, up a wall through the attic into a wall plate. That part of the run does NOT seem to be the problem as with a certain amount of fiddling with the wires between the wall plate and the sub, the hum does seem to disappear.
Is this something the ground isolator will fix, or are there other solutions I can try first?
