Jbherrin is right on with reference to the difference of potential. It's something that should be checked.
Help!! Low level hum from FM cable sgnl
I'm using my cable as an the signal input to my FM tuner(MD FT-11), but there is a terrible hum now in the system. It makes no difference if I select the tuner or not(on the preamp) or if the tuner is on or not. I'm curious if a Monster Cable power conditioner (1200 I think-the one with the cable input) would filter this out or if there is another solution. Thanks