Help with inverted phase Newbie Question

I have heard about somehow inverting power prongs might possibly resolve the ground loop/hum problem. Even though it doesn't work for me that way, it gives me the idea to try inverting the phase from my preamp. This works for me, but I am still trying to figure out why...

Alrau1: If both my preamp and CDP have phase inverted, do I need to swap the speakers leads? The reason to invert the phase from my preamp is that it could reduce the hum from my system quite a bit. Thanks.