1) Does the subwoofer amp hum with no input? yes ) Does the receiver hum when the sub amp isn't connected? no 3) When everything is connected, does the hum come from the sub, the receiver or both? both 4) Why do you run a signal back from the sub to the receiver instead of just going one way? I don't have ony splitting cables. Should I get some to see if it will cure the problem? 5) Are you using an effects output like for an equalizer, that splits the preamp from the amp section of the receiver? yes--I was thinking about changing it to running the speaker output to the high level input on the sub amp, but I was afraid that it would color the sound. ) If so, have you tried leaving the straps in place, and using another preamp output instead, like perhaps a tape monitor output? Then you can't adjust the volume of the sub though--I want to set it at the right level so they sound even at any volume. Thanks a lot again.