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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
mastering92
870 posts
 

Great, it works! 

jea48
4,258 posts
 

EDIT:

Jea48 said:

I assume the sub panel was install because the main panel was full. Three 120V circuits were moved from the main panel to the new sub panel. I assume, hopefully, to free up two breaker spaces in the main panel for a 2 pole breaker to feed the sub panel.

Add.  Evidence would be a two pole breaker in the main panel that feeds the sub panel. Might even be marked on the panel schedule.

erik_squires
15,632 posts
 

 

One equipment grounding conductor. (Note: If a steel conduit is used between the main panel and sub panel that meets NEC for use as an equipment grounding conductor.)

That's a surprise! We can't do this for junction boxes or outlets.

ieales's avatar
ieales
1,201 posts
 

I haven’t checked the code in a while, but I think it’s because a panel is more or less permanent.

With an outlet, if it’s out of the box, no earth. Gotta protect the unskilled from themselves.

jea48
4,258 posts
 

 

jea48 said:

One equipment grounding conductor. (Note: If a steel conduit is used between the main panel and sub panel that meets NEC for use as an equipment grounding conductor.)

erik_squires said:

That's a surprise! We can't do this for junction boxes or outlets.

 

Yes you can. NEC 250.118 (2) (3) (4)

 

250.118 Types of Equipment Grounding Conductors
 

The equipment grounding conductor run with or enclosing the circuit conductors shall be one or more or a combination of the following:

  1. A copper, aluminum, or copper-clad aluminum conductor. This conductor shall be solid or stranded; insulated, covered, or bare; and in the form of a wire or a busbar of any shape.
  2. Rigid metal conduit.
  3. Intermediate metal conduit.
  4. Electrical metallic tubing.
  5. Listed flexible metal conduit meeting all the following conditions:
 

 

 

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