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.