Spectral DMA 360 hum

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

Wim, I hope you are using Mit wires from your Elger to the Spectrals. If you are not you run the risk of the Spectral going into oscillation. This will fry the output
devices. A high pitched hum is an indication of oscillation. Spectral was designed to use Mit cables and nothing else...period!