Ground Loop in HT system???...HELP


I have a reoccuring hum coming thru my amp and cd player about every 5 to 7 seconds.
My equipment is McIntosh mc205 and mx136,Naim Audio CDX,Oppo 93,Furman Elite 20PFi,time warner cable box and Pioneer Elite Pro 110fd plasma tv. All on a dedicated 20 amp line.
I've narrowed it down to the tv. When the picture's on the hum is there, when tv is off...no hum. It's not the cable box either.
I had luck with an extension cord for the tv-plugged it in across the room...hum is gone. Also used a smaller LCD tv set up with in the HT and no hum. Is it my HDMI inputs on the tv? I'm lost and no one seems to the any answers. Any help would be very much appreciated. Thanks guys
mlopardi
I may be wrong here, but I suspect it's your cable tv box. How do you know it's not the tv box? Even when it's not turned on, your tv is still hooked to it, continuing the grounding pattern. The only ground loop problem I've ever had involved this box. I had to open up the box, and put a suitable ground lug on it, and then run it to ground.

This completely cured the problem. I would try it, and eliminate your tv box as a source of the problem.

Best of luck, regards,
Dan
I've narrowed it down to the tv. When the picture's on the hum is there, when tv is off...no hum.
OK...

I had luck with an extension cord for the tv-plugged it in across the room...hum is gone.
OK...

Existing for HT audio system.
Dedicated 20 amp branch circuit.
One duplex receptacle connected to the branch circuit?
What is the TV usually plugged into? Surge suppressor outlet trip plugged into one of the recepts of the duplex receptacle?

What is the audio equipment plugged into? Another outlet power strip?

Buy one of these and check the polarity at the duplex receptacle and every receptacle in the power outlet strip/s.

Check the polarity of the duplex recept you temporarily fed the TV from with the extension cord.

Check the polarity of the recept on the end of the extension cord.

Also used a smaller LCD tv set up with in the HT and no hum.
Connected by the same HDMI cable?

Is it my HDMI inputs on the tv?
Try a different HDMI cable....

Even though you say it is not the cable box.... Disconnect the CATV cable provider's RG6 coax cable from the box and check for hum. That will rule out the CATV cable.
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Thanks for your response guys. I tried disconnecting the tv/cablebox from the wall and with the picture frozen on the tv I still have an audible hum from the amp and cd player. I'm going to try all of your suggestions. Also thinking about another dedicated line for the tv(crazy???)
Called Furman and the Elite 20PFi is more than enough to handle all the gear. The drama of HT...I will stay in touch
Mlopardi,

Do you have all your audio equipment, CATV box, and TV plugged int the Furman Elite 20PFi?

I had luck with an extension cord for the tv-plugged it in across the room...hum is gone.

For a test try plugging the TV directly into one of the recepts of the dedicated 20 amp line. Check for hum.
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I tried plugging the tv directly into one of the recepts of the quad dedicated 20 amp line and still have the hum...It's got to be something simple but I still have no clue. I'll continue to try...keep the suggestions coming. Thanks guys
I have a separate receiver for HT. When that receiver is turned on, I have a similar issue, regardless of whether the TV or cable box is. When it's not, I don't, regardless of whether the TV or cable box is. If you don't have a separate receiver, you probably have to ground your TV, cable box, or both.