OK, is it just one guitar? If so, why would it hum through certain circuits and not others? Doesn't make any sense.

Wait!: difference being, your amps have 3 prong power plugs, and HD500 and probably Lunchbox have 2 prong, right? Maybe the power strip they plug in to is not grounded?

Edited 2 times by gckelloch Oct 28 13 11:30 PM.