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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.
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erik_squires
15,620 posts
 
Um, do NOT "short" your speaker wires!

The example in fig. 4 is fine, but it is most certainly NOT a short, it is the opposite, a choke.

Given however that you even have powered speakers having this issue, the problem is probably too late by the time it gets to your speakers. You need to think further upstream.

I did by the way recommend cheap RF chokes above.

Best,

E
shadorne's avatar
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shadorne
7,467 posts
 
A choke is an inductor that chokes off high frequencies.

The reason I think it is coming from the speakers and back into the Amp is because you have tried other steps.

An very strong HF signal hitting the tweeter coil might also cause core saturation (hystersis) in the tweeter and this converts HF to broadband noise.


toddverrone's avatar
toddverrone
840 posts
 
chokes are ferrites, what a bunch of us have suggested trying..

man, i hope you're single at the moment! all that foil
james1969's avatar
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james1969 OP
347 posts
 
Ferrites are on order.  I still need more aluminum foil. 👍🏻
dlcockrum's avatar
dlcockrum
2,190 posts
 
Have you thought of wrapping cords and cables with this:

https://www.ebay.com/itm/EMF-RFID-RF-Shielding-Copper-Fabric-Roll-44-x-1-of-Material/131893330384?ss...

Using this conductive tape to seal the seams and to ground the fabric to electrical ground:

https://www.ebay.com/itm/Copper-Foil-Tape-1-5-X-10ft-EMI-Conductive-Adhesive-Ship-from-USA/162095634...

Dave
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