Trytone.....I suggested the cheater to find where the ground loupe is. Try it on the turntable first (I doubt it will help there)..... also try it on your other black boxes until you find the culprit. In my system (Ayre amp, preamp, Universal silver disc player, Vandersteen speakers (which plug into the wall), and dedicated headphone amp)...if the headphone amp is not plugged in, I get a hum (with the 2nd preamp output connected).... You just have to wade through the system ....the joys of audiophiledom. Plug the 3 way plug you are testing into the "cheater" which allows you to reverse the plug (turn it 180 degrees) and/or eliminate the 3rd ground wire (the rounded metal spade on the plug...as opposed to the 2 flat ones (one wider than the other).