Eliminating Ground Loop Problem

Did you try a cheater plug or a Hum X?
I also would recommend Pm'ing member Atmasphere or calling him (Google Atma-Sphere).
He helped me track down a hum issue.
Bob

How’s that routing OP? Do you have cables laying over cables?

Cable art.. I should teach a class. It’s fun too.

Make sure nothing is touching, NOTHING. If cables cross make sure there is at least an inch between them and at 90 degrees.

Run them side by side, but NO touching, especially Power Cables (not cords) and Speaker Cables..(not wire).

You can check pretty easy by, lifting and lowering cables.. The sound will Yo Yo..

Regards

gdnrbob.

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

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?

OP a ground loop is the difference in voltage between two pieces of gear. A ground loop eliminator is BETWEEN the source and preamp/power amp. IF the noise is coming from just the Preamp, no matter the source or the power amp, that’s not a ground loop. BUT it could be a GAIN issue... from another source, don’t be fooled.

Another thing.. routers and Laptop power supplies. UNPLUG them.. Just for now... Noisy thing Especially cable company router box power supplies.. The older the box, the higher the noise level and power consumption.. My old cable box pulled 270 watts.. YUP.. I was floored, It actually required a ground loop eliminator via The Cable Company, Comcast..

Friggen ark welder... LOL

Regards

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.   

If you have the cable (tv) plugged in anywhere you need to isolate it. I have many I got for $8@.  Cable ground is NOT absolute/

FYI, the Marantz AV7702 is already lifted from ground, so you don't need any cheater plugs.  You can tell my looking at the IEC inlet on the back and seeing that there is NO ground prong.

You could try this:  disconnect all source devices from the Marantz (such as bluray player, satellite receiver, DVR, etc.).  Then see if there is ground loop humm at this point.  You can connect each source device (probably by an HDMI cable) one at a time to see if there is a source device that is creating ground loop humm. 

Another thing that can create ground loop hum is devices that are plugged into a different opposing-polarity circuit.  If you have identified a bad source device on the Marantz, try plugging it into the same outlet / power conditioner as the amplifers (same with the actual Marantz).

Sometimes ground loop can come from a cable box or a satellite receiver with improperly grounded dish/COAX wiring.  You may need to get a COAX isolation transformer - something like this:

https://www.amazon.com/Ground-Loop-Isolator-Transformer-Eliminator/dp/B08FRGH4X2

They are very easy to install inline with the coax cable that screws into the cable box or satellite receiver.  Be aware that these devices may not work on some cable boxes or satellite receivers.  Some receivers/boxes can't communicate with one of these isolation transofers on the line.  However, sometimes this can improve the image quality and the audio quality of the cable/satellite.

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.

Make sure the ATI amplifier and the stereo amplifier and preamp are plugged into the same AC circuit.  If they are plugged into opposing polarity circuits, this can cause ground loop as well.

There you go OP, Everything has to be plugged into the same circuit and after you verified that by turning on something ELSE, the noise came through the center and rears.. It sounds like they are on a different leg at the main..

One circuit
Unplug routers and PS to laptops
and do some cable art.. My system is dead quiet.. 65 year old C20 preamp point to point.. Talk about an antenna.. LOL Zero noise..

Quiet as a mouse.. Valves in all, there are a slough too.. 30 valves in my system... Quiet as a mouse.. 7 per preamp (2 C20s) and 16 in the ol Cary V12R

My oppo did the same thing with HDMI. Never could get rid of it, so I lifted the ground on the Oppo.  But beware of the grounding police.

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.

Ok I’m serious now.. I got a feeling If I routed that bunch of cables and inspected the connection including grounds between components, a LOT of the noise would go away if not all of it.
A crap cable can drive YOU nuts too. NOT ME though.. I won't stop until my system is quiet..

At least 10 times I’ve fixed system that supposed PROS didn’t fix because of routing.. You know the Stereo Only, kind of free install they get with a 20K purchase.. LOL.. They leave and you can hear arcing in the back ground.. as you tip them for their BAD work.. BUT you think it’s wonderful..

Can’t find the cat, see his tail sticking out from under one of your new 10k 200 lb speakers.. Still purring..

If the noise is that bothersome, it has to be routing at least partially..
I’m telling you you can stand by my speakers and turn the system up all the way, you have to be within 12" to hear anything.. I can hear valves hiss, ever so slightly.. My kids can’t hear it at all.. Grandson and wife can though.
A lot of valves, too.. 

Regards

Look into ground loop isolators and decide if you need them. It may not be your gear itself.

This might solve the problem: https://emfessentials.com/products/pure-power-plug-in-filter-120v

If all else fails, an electrician would be able to determine a solution for clean electricity throughout your home. This would mean installing a mains filter to  regulate electricity - keeping those sine waves linear and without high-frequency switching noises from plugged-in devices. Audio gear is especially sensitive to dips in voltage and dirty electricity.

Sometimes, radio frequencies through an outlet can manifest as hum. I'm sure you will figure it out...

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.