Built the A/B box from GGG but getting hum- any fixes out there?

[jimbob]

I recently built the A/B box to switch between a high gain amp (Peavey XXX in high gain mode) and A Supro 1624(the Supro being used in the  non gain mode) The problem is I'm getting a noticeable hum from the Peavey. I can understand the nature of the problem but wondered if there was a simple fix. I can build the A/B/Y from GGG and Geo but Id have to order a few parts and all without certainty that the hum problem would be eliminated. Ideas? Fixes?

[joegagan]

have you tried a ground lifted cable on one of the amp input leads? sometimes this will break up a ground loop.

[Philippe]

here you go...
www.fulltone.com/PDfFiles/AB_switcher.pdf

[Paul Marossy]

have you tried a ground lifted cable on one of the amp input leads? sometimes this will break up a ground loop.

That's generally the approach I take when presented a situation like this.

[jimbob]

I'll give it a try
Thanks all.

[trixdropd]

I'll give it a try
Thanks all.

I second the fulltone link. This will completely isolate the amps from eachother, while keeping all grounds intact and muting the amp not in use...

[Paul Marossy]

I'll give it a try
Thanks all.

I second the fulltone link. This will completely isolate the amps from eachother, while keeping all grounds intact and muting the amp not in use...

Yeah, I've seen that A/B box before. That will probably work. If not, then one of the ground connections would either need to be broken or isolated somehow.