[Wayne A. Pflughaupt]

If I unplug the INPUT RCA going into the BFD (from the receiver) then the hum stops. However if I take this same plug and go directly into my sub, I do NOT get any hum (even with the BFD still plugged into the same AC wall outlet as the sub).

There ya go – that means the problem is a ground loop between the BFD and other components in your system. This is probably because you have it plugged into a different circuit on a different service leg as the rest of the system. Your best bet would be to move the BFD to where the rest of the electronics are.

If that doesn’t get it, look to your cable TV service or sat dish. The CATV service and the dish should be grounded outside to the ground stake at your electrical service.

Regards,
Wayne