Bob, assuming it's not a compatibility issue, or 'common to the players', the process of elimination says it's the pre-pro. For a temporary substitution, most receivers have preamp outputs, so you can try the existing player with a different decoder.

Plus, since both players produce the noise, take the loaner to anywhere you can connect it to another pre-pro or receiver and see if you can reproduce the noise. I'm willing to bet it won't happen.

The Parasound looks like the culprit.

Larry
www.fineelectricco.com