Spectral DMA 360 hum

Sounds like a groud loop problem. Trying removing your cable TV connection from your receiver or pre. once the cable has been removed if the hum stops then that would suggest a ground loop problem. A jensen transformer ($50 bucks on Ebay did it for me)Model # VRF *** good luck

What preamp and cables are you using?

Spectrals are VERY sensitive and Spectral pre's and MIT cables are almost mandatory.

Try floating the ground on the amps using a cheater plug. I had to do this on my stereo Spectral amp to eliminate hum.