EDP and ground loop hum

["Tom Rex" <tomrex1@cox.net>]

Is it common for the EDP to cause a hum in the audio system?  I've tried
moving it away from the speakers, but that didn't seem to help.

The salesperson at the Guitar Center recommended a Morley Hum Eliminator. I
routed the cables from the mixer, into the Morley, and then out to the
speakers, and that helped a little, but there is still some hum there.

I'm going to try redoing it, and putting the Morley in between the EDP and
the mixer.

Am I doing something wrong, wasting my time?  I'm using the EDP in a
electronic music environment, and none of the other pieces of hardware 
cause
any discernible hum.

Perplexed,
Tom