Okay, here's the deal: I have a rack setup with two Trace Elliot amps, a power conditioner and another rack effect. I am finding that, if i plug a 1/4" into the line out on the front of one of the amps (so i can send signal to the other), I immediately get a horrendous buzz coming through the speakers. In fact, if I simply wave the 1/4" end over the metal sides of the rack, I get the buzz. This has happened with two completely different amps in the same rack and this obviously sounds like a grounding issue with respect to the rack because I don't have the same problem when i plug the two units into one another outside of the rack. What do I need to do to solve this grounding problem? Is there a specific type of shielded cable that I should use?