Thanks for your responses. I am in the USA and it is not ambient, amplified thru the speakers. I have tried weighting the top of the unit and surrounding the case with metal, nothing stops the hum but my bare hand grasp. As I recall, the (4) transformer bolts, attaching the it to the case have rubber washers to isolate it from the case. I'll pop the top and look for loose connections ....
Jolida JD-9A Phono Stage Hum Problem
I have tried all the settings on the rear and both outputs, put cheater plugs on all the gear in all possible combinations, tried different interconnects. This a 2 channel stereo, no video connected. There is a low level hum (sounds like a 50 or 60 cycle hum) that none of the above has any effect, however if I grab, with my hand, the case where the transformer is located (left middle), the hum is reduced by 90%, when I let go, the hum returns. Short of holding the preamp when listening, does anyone have any ideas?