Emu XL-7 & MP-7 User's Group

I tried to load OS 1.32 via E-Loader into my MP-7 and I couldn't 
figure out how to do it with USB, but that's really not the issue.  
I gave up and went to go back to working with it and there was a hum 
that can be heard with the volume up or down, both in the headphones 
and through the outputs.
Does anyone have a clue as to what this is or how it happened?
Many thanks!
Joseph