Proximity Hum And How To Eliminate It

I own a phono stage with separate power supply, whenever I put the power supply near the phono stage unit I get 60hz hum caused by the proximity of the 2 units being close to each other. 

Previously I could avoid this because I was able to locate them far enough apart. Because of circumstances I now have to place the units close to each other.

Does anyone know how I can eliminate this proximity hum, either by shielding them from each other with something or????