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high frequency intermittent noise

I have a noise issue that is intermittent.  Here is what the noise sounds like:

https://clyp.it/4b233bmm

Here is what I know so far:
  • The sound affects all components and is compounded if all components are turned on.  I have turned off my preamp, phono preamp, leaving just my mono blocks on, and the noise still appears.
  • I have turned off everything and unplugged everything in the house including my dimmer switch, and the noise still appears.
  • I have a pair of pro-audio monitors, self powered with class AB amps, and when I plug those into the same outlet, I hear the same noise coming through the pro-audio monitor.  So this rules out my big system.
  • The noise is primarily during the day and goes into the evenings, weekends too, early mornings it does not appear.
  • I live in a pre-war mid-rise building.  I have no ground, I'm using a Nordost QKore grounding system.  This did reduce the noise floor quite a bit, but has no affect on this intermittent noise.
  • I have a cell phone tower directly across the street from my building in Manhattan.
  • Looking at a real time analyzer, I see peak at 2kHz when the noise appears.
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james1969 OP
347 posts
 
It's 15.
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james1969 OP
347 posts
 
@jea48

Yes, this is a dedicated circuit, I have tested for this.

When I changed out the outlet, there were 2 wires connected to the old receptacle: white and red. There is another black wire not being used. I didn’t want to touch that wire, since I don’t really know what I am doing, I just copied the previous installation, using only the red and white wires previously used. The insulation seems to be fair, it’s PVC/plastic and the white looks white and did not appear brittle.

I would say the insulation is in good condition.

I will have someone come in and take a look at the circuit, maybe it can be switched out for a 20 amp circuit. So far though, I’ve never tripped the circuit breaker, and my amps are class A.  Thank you for the kind words.
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