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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.
james1969
james1969's avatar
james1969 OP
345 posts
 
@jea48 Thank you for all your expertise.  I will pick up that receptacle tester and check it out.
jea48
2,944 posts
 
@james1969

If the tester indicates the equipment ground is present then you will know it is not doing anything to help with your noise problem.
kosst_amojan
2,095 posts
 
I'm virtually 100% certain that's cell phone signal interference. That is exactly what an LTE signal sounds like when it's being picked up by an unshielded/under-shielded wire in the signal path. I doubt it's being picked up through the power lines, but I can't be curtain. If it was, you'd hear it through your TV and computer. I'd be looking at interconnects. 
james1969's avatar
james1969 OP
345 posts
 
@kosst_amojan  

My interconnects are all shielded, but they could be under-shielded.  If I turn everything off in my system except for my amps, I can still hear the noise.  So in that case we would look at the speaker cables, they are shielded too.  When I turn on my pro-audio monitors plugged into the same circuit or a different circuit, they exhibit the noise too (that rules out my system).  Keep in mind, these pro-audio monitors are self powered with class AB amps built into the speaker enclosure, so it's a self contained amp/speaker.

I do not have the noise on my TV or computer.

I did think about the tubes picking up the noise because on my amps, all the tubes are out in the open?  But then I had a solid state phono preamp in my system just recently, and that picked up the noise as well, so that rules out the tube theory.
jea48
2,944 posts
 
@james1969

How long have you had the noise problem? Did you have the noise before you changed out the wall 2 wire duplex receptacle outlet to a new grounding type outlet?

When do you think you will be able to pick up a plug-in circuit checker?
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