Eliminating Ground Loop Problem

gdnrbob.

Thanks so much for the information. I will certainly reach out to him.

Everything is plugged into a Torus RM20. I don't use a laptop. My 2-channel is quiet as a mouse. The noise only occurs when I'm using HT.

When I'm listening to music through 2-channel there's absolutely zero noise. When I watch a movie I turn my Marantz 7702 mkII, OPPO 203, and ATI  AT523NC 3-channel on to drive my center and rear speakers. The noise comes through my center channel speaker and rears. ATI told me to disconnect the interconnect cables from the amplifier and see if I hear a hum or any noise from the amplifier. I disconnected the interconnect cables and the amplifier was quiet. I have a wire going from the Marantz's ground to the ATI's ground. The wire reduced the noise, but didn't eliminate it. The noise can only be heard during quiet passages, but it drives me crazy.   

oldhvymec,
Yes, I'm embarrassed to admit my cables are all over the place. It's a complete mess behind my equipment rack. I will try to organize the wires the way you recommend. 

My question is why when listening to 2-channel is everything dead silent?

Thanks to everyone for their input, I really do appreciate it. 

A special thanks to Fuzztone for mentioning cable TV. I removed my cable box and connected a ROKU stick to my OPPO. Removing the cable box eliminate 99% of the noise to the point that I can only hear noise if I put my ear to the speakers. In addition, I changed from using RCA to XLR cables.