When slaving to a second amp and cab I am getting the dreaded mains hum. Tried links from send to return, DI out, tuner out and sub out, both to the return and pre-amp inputs of 2nd amp. Also get it with my Ric o Sound kit direct into the two amps. (with no amp to amp loop connection) The only way I have found a way around this is to disconnect the earth wire from the second amp, although Im not sure how safe this is. BTW this is UK 220-240 volts AC, and may not be a problem in the U.S. Does anyone know if disconnecting one of the earth (ground) wires is ok providing the main amp is earthed, or how I can solve this problem?