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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
erik_squires
15,673 posts
 

The ground and neutral should only come into contact at 1 place in your home, at the service entrance.

If this is anywhere else then this is bad.  Check the N to G voltages on your circuit with everything disconnected.  Should be zero.

erik_squires
15,673 posts
 

Also, check the usual suspects.  Did you also introduce or mess with a coax cable to a set top box or modem?

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.

 

ozzy's avatar
ozzy
7,211 posts
 

As Erik expressed, somewhere within your system you are picking up the ground noise. Try a plug cheater adapter to lift the ground just to see if hum goes away.

If that does not help, try disconnecting cabling that comes from other sources outside your new dedicated line.

ozzy

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