Craig, this could very well be 60Hz "hum" possibly due to a poor ground on the Odyssey amp. If you have a volt-ohm meter, remove the interconnect cables and measure between the case on the amp with 1 probe and the case on the receiver with the other to see if there is any voltage potential betwee them. If there is (and it may be quite small) you'll need to double, no triple check the ground on the new amp. good luck and let us know how it turns out.
Bob