Wadia 121 Ground Loop Hum

I have a ground loop hum in my system that seems to be caused by my Wadia 121. If I physically apply pressure to the power supply input and the usb input cables the hum will go away (it also it not present if I throw my dac magic in with this system to replace the wadia). I am assuming that I need to send the unit in for servicing. Does it sound like I am on the right track, or are there any other diagnostics that I should try before contacting Wadia?

Thanks,
Jim