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?
Ag insider logo xs@2xo_holter

Showing 7 responses by o_holter

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o_holter OP
956 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).
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o_holter OP
956 posts
 
Thanks for help! No neon signs nearby, no special equipment on, in our house. The noise is regular with 8 m 30 s intervals. It comes and goes a bit, and sounds like a wireless interference, much like standard mobile phone interference, except it is regular - rather than AC interference. We do have a security system in our house - I will check, could this be the cause.
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o_holter OP
956 posts
 
almarg - you were right. I unplugged the main alarm system control box and disconnected the battery. Now, the noise was gone. I will get service on the system tomorrow. It is both wired and wireless.
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o_holter OP
956 posts
 
The solution so far - the installer moved the box out of the room with the stereo system, and up to the second floor of the house. Now the noise was gone. It comes from the GSM chip in the controller box (made by Honeywell) he told me.
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o_holter OP
956 posts
 
I no longer hear the 8-minute bursts of noise, since the alarm control box is further away from the system. Now it is close to our bedrooms. And I wonder, how healthy is this, with such strong bursts? The installer did know about the problem, but they did not announce it (of course). When I asked for a better shielded control box he just looked at me. Then I asked, well, since the noise is produced by the wireless part of the box, can we have the alarm system wired, then? He answered: we don't do wired installations anymore.
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o_holter OP
956 posts
 
Thanks, Al. The transmitter was close to 8 METERS from the system, and yet the speakers made noise like mad. I am not in the "very worried about exposure" camp, but it was quite special. It is the pulse that matters (15-20 seconds per 8:20 minutes). If the specs only give the average radiation, they won't tell the full story. Thank you for your input, I will investigate some more. 
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o_holter OP
956 posts
 
Yes, Al, your diagnosis was spot on. It illustrates the importance of describing the symptom precisely. It was only when I timed it, after just having been irritated by the burst of noise coming and going, that I started to make progress. I found that it was regularly periodic, like I described in the start of this thread. I got a lot of suggestions, and one of them hit the mark. Grateful to you all, and a happy new year.
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