Ground loops on guitar with multiple outputs

Hi, I have friend with a guitar the uses a number of different pickups in unusual places (a piezo under the nut for instance), there a re 5 outputs all up. Up till now he has run the outputs from the guitar (using a 6 pin xlr connector to box with jack sockets) into a little mixer and then into a guitar amp which works fine. What he now wants to do is experiment feeding the different outputs to different amps which of course creates earth loops. The 2 solutions I can think of would be to transformer isolate each output or to run seperate grounds for each of the outputs. The transformer idea is a bit more expensive the he would like and the seperate grounds sounds difficult in terms of finding a nice connector and cable to run from the guitar. Are there any easier/cheaper ways to fix this problem?

Any help would be much appreciated

Cheers
Dave Cooper

Using separate cords from each pickup and keeping them electrically isolated from each other should prevent ground loops.

JR