O'Kay; lets see. Can you indicate if there are any other grounding schemes you are using on the rest of your set-up? Like three into two prong plugs or say; Plugging your amp into the back of the pre-amp, those kind of things. I had a problem once with the wall out let forming a ground loop and the only way to alleviate it was to float the pre-amp by removing the third pin; the ground pin on it's plug. Next can you tell a little about the pre-amp; what it's phono stage looks like; does it have a ground screw or post dedicated to the phono?