Consider snap-on ferrite beads. Relatively cheap. Worth at least experimenting on interconnects and power cords.
http://amzn.to/2hLhLG9
Best,
E
http://amzn.to/2hLhLG9
Best,
E
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:
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.
- ...
- 157 posts total
@james1969, I missed the Big Glass Window directly behind your audio gear when looking at your system pictures before. Just a test you can try, if you are up to it. Cover the entire window with at least two layers of aluminum foil. Tape the foil in place. Overlap all splices by at least a couple of inches. Overlap the second layer by 1/2 the width of the aluminum foil. If possible wrap the foil over the window inside trim to the adjacent wall, window sill, and above window trim. Ground the aluminum shield to the mains equipment ground with a piece of wire. For the ground connection of the wire to the aluminum foil you could try removing the insulation from the wire several inches and then tape the bare ground wire to the foil the entire bared length. If by chance it works, fingers crossed, you might then try copper window screening to cover the glass window. EDIT: If you do try the experiment, experiment with the foil shield grounded and un-grounded to the mains equipment ground. Example of copper screening. https://www.dkhardware.com/bronze-copper-zinc-60-screen-wire-50-BRZW60-product-49932.html?gclid=EAIa... almarg and or kosst_amojan, or others, Would the copper screening work well as a shield and reject RFI from entering through the glass window? |
@jea48 I'm with you man. Check this out: https://www.select-fabricators.com/rf-emi-shielding/rf-emi-test-shielding/curtains/ I need to get more aluminum foil... |
almarg and or kosst_amojan, or others,Yes, Jim, I would think that a grounded copper screen would be effective against 700 - 800 MHz, since the openings in the mesh are far smaller than the wavelengths of those frequencies (which are about 17 and 15 inches respectively). Although as noted at the FCC link I provided earlier those frequencies can "penetrate buildings and walls easily," so keeping them from getting in via the window might not be all that helpful. Good suggestions, though, in your previous post. Best regards, -- Al |
This RF/EM signal must be picked up by the voice coil in the tweeter and it is likely a powerful megaHz signal and would be inaudible if it didnt cause problems for the amplifier(which tries to surpress distortion with negative feedback so as to match input) and the problem manifests itself in the audible range somehow due to signal saturation in the amp section making it a broadband signal. Try adding a choke across the speaker wires to short out the HF signal. http://audiosystemsgroup.com/RFI-Ham.pdf See Fig 4 for an example... |
- 157 posts total