2. analog
  3. 127317-5312

Periodic noise

My system picks up noise every eight minutes. There is a kind of scratching mid-register ("ta-ra-ta-ta") sound that last for ten or fifteen seconds. It is similar to descriptions of "GSM buzz" but it happens regularly and regardless of whether our mobile phones are on or off. It happens when the analog source is selected, not other sources (or not obvious, in my system). It is very clear when the volume is mid-high, with no music playing. It is not from the cartridge and the tonearm cable, since it happens even when I disconnect them from the phono stage. When I disconnect the phono stage, however, I don't hear it. So it seems to be picked up from the phono stage itself. It happens across different phono stages. Shielding the cables with ferrite does not help much. It seems like a very strong signal.

Anyone recognizes this problem?
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Showing 3 responses by lewm

lewm
12,556 posts
 
One approach to figuring this out would be first to determine whether the noise is getting into your system via the AC line or via the air.  If you have or can borrow an AC regenerator or some sort of very good AC filter, see if that makes any difference.  (Of course, RF is often so high in frequency that it gets by any sort of commonly used filter, but it's worth a try.)

Perhaps also you can fashion some sort of Faraday cage and place it over your phono stage, in hopes of blocking airborne interference.
lewm
12,556 posts
 
Matt
What makes you think this is likely to be a grounding problem?

lewm
12,556 posts
 
My wife signed us up for Verizon Fios.  At one point, the Fios was going down with regularity, until I finally investigated our circuit breaker box, where they had installed an AC outlet to power their system, which is a simple plug-in.  It was easy to demonstrate that power to the plug was intermittent, by simply wiggling the plug, causing our problem with lost service.  When I opened the housing for the new AC outlet their tech had installed, I found that the wires were nearly floating free in the box, just barely in contact with the outlet, because of sloppy attention to detail.  At least it was easy to fix.  Then I noticed that the Verizon crew had tapped into my dedicated AC lines to power the new outlet they installed for Fios, thus assuring that my audio AC was constantly polluted with digital garbage. You've gotta keep an eye on these installers.

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