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Hum in Speakers with New Dedicated 20 amp Circuit

I just ran some 12-2 from a new 20 amp breaker and installed a dedicated outlet for my system. Now I get a very audible hum in both channels. If I switch back to the shared 15 amp outlet, no hum. I checked the new outlet with a tester and it checks out as wired correctly. At the electrical box, the black wire is connected to the breaker and the white and ground are attached to the same ground strip. I’m using a 20 amp receptacle.

Anyone with thoughts on how to resolve?

mjjw

Showing 5 responses by mjjw

mjjw OP
8 posts
 

Winner Winner Chicken Dinner!  Ground loop…duh!  I had the stereo rack plugged into the new, dedicated circuit, but I had the subwoofer plugged into a separate outlet that was not on the same circuit. Moved the subwoofer over to the dedicated circuit and…viola… no hmmm. Thanks all!  

mjjw OP
8 posts
 

No coax in the house. I turned off any fluorescent lights. I checked the buzz with my piano tuner. 60hz. Have tried two different amps, same result.

Here is a pic of the electrical panel. I color coded it. Yellow is the coming wire. Black hot. White is neutral. Green is ground.

 

mjjw OP
8 posts
 

Should the ground wire go to the block with the green screws instead of the neutral strip?

mjjw OP
8 posts
 

NB: I didn’t install the sub panel; I just added an additional breaker.  The sub panel has been in for almost a decade.  I have an electrician look it all over and correct as necessary.  Thanks all.

mjjw OP
8 posts
 

 

Just returned from a long trip.  Want to thank everyone for the useful info.  I'm sorry I was not able to post more detailed pictures sooner.

Here are detailed pictures of both panels.  The conduit between the panels is indeed PVC.

Let me know if your thoughts.

 

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