GSM-noise "buzz" issue

Florian Zeitz florian.zeitz at
Fri Sep 19 22:23:32 CEST 2008

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Werner Almesberger wrote:
> Andrew Bruno wrote:
>> So I ask OM... what's the average user to do? One that's not too steady
>> with the soldering iron :)
> I just wonder ... has anyone tried to make an audio plug that just
> shorts MIC to GND ? Or, for simplicity, that just shorts all four
> contacts to each other ? I think such a "headset suppressor" could
> be made fairly flat, maybe protruding one millimeter.
> The switch between the internal and the external audio paths is
> controlled by software, so this shouldn't affect the internal paths
> very much (only MICBIAS is shared, but it's protected by R4408,
> 2k2).
> Some of the test results from Taipei suggest that this won't help,
> but given that not everyone seems to experience quite the same
> symptoms, it might be worth a try.
> - Werner

FWIW I have tried something similar. I put a small (100 Ohm IIRC)
resistor between MIC and GND, that doesn't help at all though. It just
makes things worth. If you think it's more likely to work I can try a
short everything or a completely different approach (still have two
2.5mm jacks lying around) if you want.
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