Could be a noisy tube......
If you think it is ground loop problem (you have to be sure) fine a dealer and ask for loan of a Ground Zero made by Granite Audio. (if you are in tri-state area - let me know). I had a similar headache just a while ago. Turn out to be a "noisy" tube in one of my amps.
Cheers
If you think it is ground loop problem (you have to be sure) fine a dealer and ask for loan of a Ground Zero made by Granite Audio. (if you are in tri-state area - let me know). I had a similar headache just a while ago. Turn out to be a "noisy" tube in one of my amps.
Cheers