Loud hum in one channel

when you say it moves when you "switch leads", do you mean when you swap interconnects from the table to pre, or when you swap cartridge/headshell leads? I assume you mean the former, and in that case I would suspect a poor connection at the headshell (ie as the easiest to fix issue), if it's not that, then it could be something in the tonearm wiring. I would start by double checking a good fit of your cart/headshell connects.

Do you get the same hum when operating another piece of equipment like a transport? If so, it may be your processor. I had the same problem and it turned out to be a grounding issue. I had to plug the left channel mono amp into a three to two plug converter, then into the dedicated PS Audio receptacle. Problem solved. Just food for thought. If I switched IC cables the hum came through the other channel so it became obvious that the problem was with the processor, not the transport or mono amp. At least that was my experience. Maybe it is helpful.

The hum switches when I swap interconnects from the table to the preamp, and the noise only happens when I am using the preamp setting for the turntable; in other words, it does not happen with the CD players. BTW, the noise is present even when the TT is off, and with JUST the ground wire attached and not the interconnects; is that weird???

Hurricane: You indicated that the noise is present even when the TT is off with just the ground wire attached (not the ICs). When you hear that hum is the preamp set to TT? What if the preamp is set on "CD" for example. With the TT off and the CD off - do you still hear the hum? What if you disconnect the ground wire as well when the TT is off - still got the hum? I'm still a bit suspicious of a grounding issue in your pre amp.

Puerto, yes the hum is present when the preamp is set to TT but not on CD or AUX. I will disconnect the ground wire as soon as I get home and report back. Thanks for your help!