Hi SUBnet,
As Hansang notes, the ground isolator WILL fix everything. But you might get lucky and not require it. Do try the ground screw if there is one on your EP350. We have made some upgrades and the manuals have not kept up.
With my own EP500, I solved the ground loop hum by connecting the EP500 to a different AC electrical circuit on the other side of my living room. I didn't have to use the ground isolator.
And to answer a previous question, yes, the cable-TV box can deliver ground loop hum even if it's turned off and disconnected from the AC power source. It's the ground (shield) side of the cable that is at a different electrical potential than the rest of your system and that causes the hum. Disconnecting the cable-TV feed from your wall outlet or at the cable box input is the only way to confirm if that's the source of the ground loop.
Regards,
Alan
