I have tried 4 receivers (SX-3800, 949, 880, 680) and two sets of cables, All the receivers hum when I plug the RCA cables into the back into the phono (nothing else hooked to the other side). One set is a monster 6' gold connector version, the other is a 3' cheapy. The hum goes up with the volume. I have cleaned all the connectors very well also with Deoxit. The turn table works fine with my fathers new Sony with AUX, and a phono preamp box. Now, when I plug the cables into the AUX on the vintage receivers, there is no hum, but once I hook the phono preamp box into the aux the hum comes back! I am really stumped here. All the vintage receivers can't be bad... Yes I have tried the ground wire both tests and it barely helps the hum. I'm not sure what to do next, thanks.