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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
 
  • The noise is not affected by the volume.
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james1969 OP
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  • This noise comes and goes apparently at random.  I can go 15 to 20 minutes with out it presenting itself.  Other times during high activity, it will last for 15 to 20 minutes at a time with shorter breaks.  Early mornings it's very infrequent if not there at all.  Usually by 11am it begins.
  • I have neighbors above me, below me and to my sides.  Who knows what kind of electronics, dimmers, appliances they have.
erik_squires
15,874 posts
 
Do you have any sort of Wifi or security system? Also disconnect incoming network and cable TV cords as well if any.

If this is purely a power issue, in the audible spectrum, Furman power conditioners with LiFT and SMP are really really good for removing noise at an affordable price.

Best,

Erik
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james1969 OP
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@erik_squires I unplugged my AV system completely, cable modem included.  It was all off and unplugged.  No affect.  Thanks for the pointer to Furman, I'll check them out.
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james1969 OP
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  • PS Audio Noise Harvesters' lights do not correspond to when the noise appears, so they are not sensing it.
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