I have been working on quieting the background noise in my room and noticed a slight hum from the speakers. After some investigation, the noise is not there until the rcas are connected to the 975. Rotel and Parasound amps both amplify the hum the same. I tried grounding the 975 case to the amps case and the hum increased.
Any ideas on things I can try?

Standard ground loop troubleshooting. If you have a cable service coax feed to the system, start by disconnecting that.

will do thanks!

Had a problem with my 975 HDMI connected to my Plasma fixed by "Hum-X". $50 online.

Also had Blue Jean cable make a set of shorter unbalanced cables to work with my 7500 amp. Previously had a 990 in use.

Realized there was one more hum that was bleeding thru and there was no logic to its origin. I added a Harmony Ulitimate remote which has a control hub/Blaster. When I installed that and was moving it around weird things started to happen.

I summoned Amazon to send me another Hum-X and used it for the 7500 Amp. It seemed to do the trick and removed it.

The hum is back!!!!!!

It comes and goes. When it comes its bad. Any quiet passage in programing and its noticeable. Its not volume sensitive. Never had this with balanced input/output from 990 or

I have internet cluster of routers and cable box (fed not by coax but cat5) on top of the 975 on the rack/console and there is likey interference.
No matter how much I try its just a damn mess of cables. I was hoping moving form the 990 would help me simplify and maybe even obtain a cleaner environment but I have made more of a mess. Looks like another Saturday on my hands and knees moving about. Too many black boxes and power supplies back there.

So many items nowadays are powered by those nasty little wall warts, which in most cases are switch mode power supplies designed to a (low) price point and have almost no filtering. They are a noise source. Do some research - there may be a simple way to quiet them down - maybe a ferrite bead around their output wire.
Peter: any advice from your tech folks?

The Hum-X is good for low current draw devices, like your TV and source devices, but is not meant for high current devices like a power amplifier. Essentially, you are throttling the amp; as such, you do not want to plug the amplifier into the Hum-X. When you are experiencing the hum, start by powering off devices that are likely to cause interference and see if it has any effect. If there is no change, each piece of equipment will need to be isolated and connected to the system one at a time, starting with an isolated amp with no inputs directly to the speakers.

Also, volume control not effecting it hints that the problem is after the volume control. If the hum comes and goes, I would suspect either interference or DC on your AC mains.

I had a wall wart supply for an external hdd get leaky for some reason and create a hum just as you describe. No idea why it would suddenly create an issue as the drive had resided in the same spot for over a year.

Start unplugging devices one at a time until it stops. Have you had any extreme weather recently? Good luck and hope it is something simple.

The saga seems to have a good ending!

The last of the hum seems to be gone after moving the routers and cable box away from the 975 and adding some ferrite to the Harmony remote hub and moving the demonic little blasters! I even added Ferrite to them just to let them know who was boss.

To sum up, the above along with a Hum-x on the plasma and going from 9 foot unbalanced cable to 24inch also contributed.

Last nite I was putting everything back and making sure the transmitters with the remote were doing everything right and was turning the TV on and off a few times when all of a sudden it stopped working and would not turn back on. I unplugged it but that did not work. The panasonic power indicated red LED was blinking, its way of telling you something is wrong. When I googled my model number and this LED sequence I found "Red codes of Death" and to my horror and joy thought I might be shopping for a TV this weekend. Its a 7 year old 58in Plasma and other than having a bit of a wide frame and a fan to cool itself from the heat it throws off its an amazing picture and Im not ready to replace yet. Wife looked at me and said "Your not doing this on purpose, right?" I replied, "truth be told, I'd rather blow up the Sub's and replace those!" I unplugged the Plasma one more time and let it sit for a minute and it seemed to reset itself.

In the process of calibration I did discover one of my M&K Subs was not turning itself on and when it did, it was not putting out. After some cable swaps I took it apart and replaced the plate amp with one I had bought years ago as a spare. once done and repaired I was able to notice what had been missing and the system now is all back together and I'm having fun listening to music with the new 975 doing a great job on 2.1 stereo way above what the 990 did! with my woofers now working and calibrated via the velodyne SMS-1 I am one happy Outlaw!!!!

Thanks for all the help and suggestions!