REL subwoofer with old McIntosh tube gear?

Thanks Wolf...what does 'lifting' the ground mean?

Thanks, tried grounding to chassis to no avail. I'll try the two prong idea...thanks much.

Two prong adapter made the hum much louder...:/

Thanks. The Amps are Mc-60s and I've got the REL T-7 wired to the speaker outputs..8ohm/com. I tried jumpering to ground..no change.

The hum is pretty slight but definitely there only when the amps are on..

Thanks Al. Are you sating I should jumper both amps from common to ground even though the black wire from the REL is only connected to one?

Thanks very much. I'm assuming there should never be a hum...even a slight one?

Got it...I'll try it. Thanks!