is your cable tv near the system? if yes, it may be that you have a ground loop. try disconnecting the coax cable from the cable box and then turn on your system to see if the hum is gone.
houstonreef, while I do not have the JC1, I did own the A21 and also had issues with the humm/buzzz. I found that the amp was very sensitive to how well the interconnect was seated. Only a slight mis-seat would cause a buzzz. Try wiggling the interconnect around and make sure it is pushed all the way in. I hope this helps.
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