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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

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.
kosst_amojan
2,095 posts
 
LTE is an evolution of GSM. It uses a combination of TDMA and FDMA. The various high speed pulses are the individual data packets broadcast in the data windows. Their intensity is the product of the frequency their transmitted on and how well tuned the antenna is to them. 
To be honest I'm surprised an antenna across a street can do this. Another possibility is that somebody very near by has a picocell or a femtocell installation in their unit. That's common in larger cities. I wouldn't be surprised if unshielded tubes picked this up. Something somewhere needs more shielding and I'd be focusing on that as much as possible. I'd be tempted to build a Faraday cage and put gear inside it to see what happens. 
jea48
2,944 posts
 
Thanks kosst_amojan for the info.

@james1969
Got any of these things around or one of your close neighbors?
http://hetnet.com/what-are-small-cells-a-basic-guide-to-femtocells-picocells-and-microcells/


james1969's avatar
james1969 OP
345 posts
 
@kosst_amojan

Faraday cage is the next logical step, if the power is clean and the Furman has no affect on the noise.  I've found some copper mesh curtains I can put up behind my system, which would create a barrier.
james1969's avatar
james1969 OP
345 posts
 
I'm not aware of any picocells or femtocells in the building.  With a cell tower right across the street, I get good reception in my apartment/building, so no need for devices like those.  All though, I cannot be certain about my neighbors, anything is possible. 

It's 4:45 and rush hour is upon us, I can hear the trains below, and the noise through my system. 👍🏻
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