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?
o_holter
erik_squires
16,892 posts
 
Power off any othere dvices in the room you can. Routers, switches, thermostats (if WiFi enabled), cable TV, satellite receivers, etc as well as light switches, wall-wart chargers, anything at all that draws electricity.

See if this helps any.

Next, disconnect the phono stage from the AC outlet.

Fluorescent / high efficiency light bulbs, etc. can also contribute. Let us know.

Erik
o_holter OP
980 posts
 
Thanks! The noise is periodic and regular, every 8 minutes 30 seconds or so. Therefore, light bulbs, chargers, dimmers, thermostats etc are unlikely suspects. Turning off our wifi router, TVs and mobile phones etc is no help, the noise comes anyway. The noise sounds like wireless interference, it comes and goes a bit (but is not a radio station signal, more like a data packet burst).
lewm
13,765 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.
gdnrbob
4,508 posts
 
I recall a post where someone realized that a neon sign downstairs was causing the periodic noise. YMMV.
Bob
totem395
390 posts
 
The time interval between occurrence being every 8 or so minuets 
has me scratching my head.

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