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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
jea48
2,944 posts
 
james1969 OP
296 posts                                                                          11-17-2017 3:58pm

Playing with the Hf35c Rf Analyzer I pointed it to the cell towers across the street, and the noises it makes is higher up in in the frequency range of 1600 - 1900MHz. Where as the frequency my stereo is picking up is in the 700 - 800MHz range. So I guess it’s not the cell tower.
@james1969 ,

By chance does the Analyzer have the ability to indicate signal strength as well? If so walk around your apartment and see where the signal is the strongest.


Next go out the entrance door of your apartment to the central House hallway, corridor, of the floor you are on. Walk the hall in both directions and check for a hot spot in signal strength. Point the device at both walls on each side as well as the ceiling as you walk down the hallway.


james1969's avatar
james1969 OP
345 posts
 
@jea48 

The signal strength is an audible on the Analyzer, not a visual indicator, the speaker emits the raw signal noise.  I walked around on my floor and the Analyzer was pretty quiet.  I circled the entire floor...nothing.
james1969's avatar
james1969 OP
345 posts
 
Here is some interesting shielding:

https://hollandshielding.com/content/Filemanager/PDF_Catalog%20cable%20shielding%20[English]_November-18-2010-219pm.pdf


erik_squires
5,268 posts
 
I'm afraid it turned into a long thread. Very sorry the Furman didn't work out for you. :(

I'm not clear on something. Does this problem occur with just the bare amps / powered speakers, or does it require a preamp / interconnect to be present?

Best,

E
james1969's avatar
james1969 OP
345 posts
 
@erik_squires 

No problem, I have 30 days to return the Furman.  But I think it's a keeper.  The issue presents itself with only the bare amps turned on.  I was using only 1 amp only for some testing.  Even the powered speakers have this issue.
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