A quick question?

A little hum is normal on a lot of tube gear from my experience.

Did you try the cheater plug on the pre-amp? Also try a shielded interconnect.

Thanks guys. All of my interconnects are shielded and I tried a cheater plug on the whole system via my power conditioner. I only hear the hum when I put my ear to the speaker, not at all from my listening position. With every other component turned off the hum was still there with my amp, making me think it's transformer hum.

Yup, 60Hz floating thru the transformers & into the speakers... I have it from ONE of the two amps, go figure. As it's barely perceptible with my ear glued to a woofer I don't worry.
Or should I? (Sean?)

I'd try to isolate the problem by connecting components in reverse. Ie start with just the speakers connected to the amp with everthing else disconnected. If no hum then add one item at a time. Ie a pre-amp to amp cable, then the other one then the pre-amp, and continue until you get the hum.

May also need to use ac cheater adapters on each component.

Tranformer hum is usually a 60 cycle vibration. If it were the source, the amp will vibrate and the speaker woofer should be quiet.

Other sources of noise can be anything with a motor, flourescent lights, electronic dimmers, items with high/low switches and computers. Try temporarily disconnecting suspect items to see if hum disappears.

Hope this helps. Hum problems can be aggrevating.