I am basically in the exact same boat right now. My sub hums only when the LFE cable is connected, and the hum is actually louder when my receiver is turned off. This suggests that the LFE cable I have is picking up some noise on his own, and when the receiver is on the buffers and impedance help reduce it, but its still there. I am going to get a shorter/better LFE cable and see if that fixes the problem.
So far I havent found any cable isolaters that work wit HD satellite directTV, so not sure if I should try that, though I have read a lot about cheater plugs. They seem to fix the hum most of the time, but people say they are dangerous. Would be interested to hear updated info on the idea of permanently installing cheater plugs into a system. I cant turn my sub up higher than 1/4 gain without a bad hum....
So far I havent found any cable isolaters that work wit HD satellite directTV, so not sure if I should try that, though I have read a lot about cheater plugs. They seem to fix the hum most of the time, but people say they are dangerous. Would be interested to hear updated info on the idea of permanently installing cheater plugs into a system. I cant turn my sub up higher than 1/4 gain without a bad hum....