high frequency intermittent noise

I have a noise issue that is intermittent.  Here is what the noise sounds like:


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.
128x128Ag insider logo xs@2xjames1969
Hey, that's impressive use of perspective. Plenty of members on here are so OCD, they'd be miserable and only able to hear the noise.

I was that way with transformer hum, until I decided not to care
It's all about the music...once the needle drops...I'm very happy.

I was on a quest to solve the noise (which I have lived with for some time) and in the process, I resolved a ground loop issue, and inserted an isolation transformer which really did solve a lot of noise from my power mains.  So the system sound has been elevated, just not 100% dead quiet like I would prefer when sitting right up next to the speaker listening for noise.

Time to move on to the next weak link...👍🏻
if you are in NYC, you do what some sports car owners do - have a site outside the city where it is kept and subway out to it for a drive (or in your case, a listen)

a place in the Catskills could contain your most sensitive equipment and something else used in the city