[alsa-devel] Bug#701498: hda: Internal mic does not work on Thinkpad T420s (CX20590 codec)
david.henningsson at canonical.com
Mon Feb 25 07:16:28 CET 2013
On 02/24/2013 08:59 PM, Ben Hutchings wrote:
> On Sat, 2013-02-23 at 20:42 +0100, Adrian Lang wrote:
>> Package: src:linux
>> Version: 3.2.35-2
>> Severity: normal
>> There are two microphones in alsamixer and Gnome 3 audio settings (i. e.,
>> pulseaudio), but I can't get any sound using either of them. I think that's the
>> same problem as reported to [openSUSE] and [Ubuntu].
>> The problem persists with 3.7 (3.7.8-1~experimental.1) from
These are different bugs as they concern different hardware.
> I happen to have a Thinkpad T420 with the same audio codec, and the
> internal mic works fine. (There does seem to be a problem with external
> mics, now that I check, but let's ignore that for now.) So this is more
> board-specific, not chip-specific, behaviour.
Ok. For the internal mic, this could be the cancelling out problem; see
the "Inverted Internal Mic" section of this blog post  for more
...as these bugs can sometimes be very specific - when the factory
finally assembles the laptop, they might select a different component
just for the DMIC, that has this problem.
David Henningsson, Canonical Ltd.
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