I have used them before but never experienced this problem that really rains on my parade. I use a Focusrite 2i4, Garageband and a Fender Mustang III V2 amp, and of course my SG! I monitor through headphones but when setting it up to the monitors the hum is loud and of course increases with the volume. It is not useable. I did not find any difference with Amplitude or GB amp presets. The hum comes on as soon as the speakers turn on. The only thing that i can think of is that this is now set up in a new house. Could the poor electrics be the cause? Ideas? Thanks folks.
By process of elimination i got rid of it. It only did it when i plugged the RCA adaptor i to the headphone jack of my macbook. I switched the configuration of output audio in Logic and the Mac. It eventually shut up. Who knows?