it's probably a ground loop. You can either use cheater plugs or you need a ground loop isolator. Is the cable tv near by the system?
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Removing the ground pins is the exact same thing as using cheater plugs, you've broken the ground. No hum but it's fairly unsafe. It likely is in fact the cable, but having an eletrician out isn't a bad idea if you can afford it, he should be able to offer a safer more permanent solution. Good luck and happy listening!
01-21-07: WeiserbThe cable may very well be the problem. A difference of potential, voltage, between the signal ground of the cable coax and that of the equipment/signal ground of your audio system. Disconnect the cable TV coax from the HT receiver, if the hum goes away it is the cable that is causing the problem, not the grounding system of your home. Post back your results....
I did already disconnect the link to the cable by removing the connection between my receiver and my preamp. that did not change anything . Only removing the ground pins solved the problem. I can disconnect the cable line and see if that changes anything. I think it has something to do with the way the outlets are wired to the electrical panel. FYI I looked up ground loop on Wikipedia and got a ton of really cool stuff to read on ground loops, detection devices, and more. probably 50 pages of information. But my # 1 trusted source is Audiogon. I have never had an unresolved problem once posted here.
Update. I spoke to Ryan at PS Audio and he said that there is a different grounding potential on the circuits powering the front end and the power amplifiers , and an electrician should correct the above and add an isolated grounding rod for all circuits for the stereo. In addition as mentioned above connecting the cable line may reintroduce the problem and require an Isolation Transformer from the Jensen company.
I am having the same problem with my McIntosh C-2200.
I had a dedicated AC outlet installed. I still have the hum. I used cheater plugs and it reduced the level of hum. I notice that with my Velodyne DD-15 hooked to the aux pre-outs, the hum is present with the pre-outs switched on, but not present with them off. I have used different patch cables on the DD-15, but still have the hum.
The hum only happens on tube warm-up. When the C-2200 is "warmed up", the hum goes away...
I'm going to Radio Shack 1st thing today to get the ground isolation transformer. In any event, it can't hurt, right (?)...