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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
 
@georgehifi He wanted to have the best possible sound off the grid, so he went with a battery power supply.

@erik_squires Good idea, I just did what you suggested, but it did not work.  I even turned off all but the mono blocks, so it was just the left channel and right channel amps on, nothing else in the household.  The intermittent noise appeared.
randy-11
1,913 posts
 
if you turned off all wifi routers, then try turning off the cell phone tower

or last chance, try a different circuit - wall outlet
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james1969 OP
347 posts
 
@randy-11 The cell tower..next time I see them working on the tower, I’ll wave them down...hey can ya turn it off for a few?

Another circuit, yes I’ve tried that as well. Good idea though. I wish I knew how to use an oscilloscope and had one handy. This was very interesting:

https://www.youtube.com/watch?v=BFLZm4LbzQU

I would like to measure the Furman product with an oscilloscope to see the difference.  Has anyone tried to measure Common Mode Noise from a Furman?
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almarg
9,670 posts
 
If you have a portable battery powered AM radio, try tuning it to an unused frequency toward the low end of the band (e.g. 540 kHz), and see if it picks up the noise.  That might help to determine if the noise is getting into your audio system via the air or via the power line.  And if it turns out that the radio picks up the noise, you might be able to determine the direction it is coming from by trying various orientations of the radio's antenna.

Good luck.  Regards,
-- Al
 
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falconquest
1,108 posts
 
I did lots of research into balanced power a while back and although I went with a different unit for monetary reasons this is the unit I would have purchased. Yes, it's professional grade but so what? If it takes care of your problem then it’s worth it.

http://www.furmanpower.com/product/20a-prestige-symmetrically-balanced-power-conditioner-P-2400%20IT
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