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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.
128x128james1969
whart's avatar
whart
2,720 posts
 
@james1969 - no, I was not. I was thinking of that braided stuff that is sold by electronic parts wholesalers or specialty suppliers, like the guy that sells the Duelund? cable that in certain cases needs shielding.

I reserve tin foil for hat lining, but make sure it covers the back of my neck. :)
almarg's avatar
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almarg
9,670 posts
 
Jea48 11-17-2017
...how about when james1969 used the pro-audio monitors for the test. When he hooked them up he heard the same RFI noise. Just a guess the amps are SS.
Yes, I had thought of that, and the fact that the same noise occurred with both amps does make it seem less likely that the possible absence of stopper resistors is a factor. But note that Ralph’s comment referred to the use of such resistors in solid state as well as tube designs. (Of course, in the case of a solid state design they wouldn’t be referred to as "grid stopper resistors," that being the term I used in connection with James’ tube-based Lamm amplifiers).

Best regards,
-- Al


james1969's avatar
james1969 OP
345 posts
 
Tin foil had no affect on the power cord.
james1969's avatar
james1969 OP
345 posts
 
For those who thought the noise is GSM, I did correlate the noise with the Hf35c Rf Analyzer, but the device only correlated the noise, did not show me the frequency.  I think it was a defective unit in that the display did not work properly.
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