Did you try the cheater plug on the pre-amp? Also try a shielded interconnect.
A quick question?
I know this has been addressed ad nauseum so bear with me. Just got new speakers (Sonus Faber Grand Pianos) and I'm hearing hum when I put my ear up to the speaker. It is definitely from the amp because I turned things off one by one to isolate. I tried a cheater plug but it didn't work. Is this level of hum, very low, normal? My amp is c-j 11A.