[alsa-devel] Sound distortion with Realtek ALC889A

[Damien Brossard]

2009/10/30 Simos Xenitellis <simos.lists at googlemail.com>

> On Thu, Oct 29, 2009 at 2:21 PM, Damien Brossard
> <brossard.damien at gmail.com> wrote:
> >
> > Hi.
> >
> > I recently bought a Gigabyte GA-MA78GM-S2H motherboard. This board uses
> the
> > (in)famous (from what i've read for now) alc889a chip. While playing 5.1
> > content, I can hear noise or distortion coming from the center channel. I
> > can not test my configuration with another OS, so I can't fully dismiss a
> HW
> > problem. However, i made several tests with 5.1 and 2.0 speakers which
> > points me to soundcard problem.
> >
> > I've made some tests with speaker-test (speaker-test -D surround51 -c 6)
> :
> > 1) Each time a sound is played either on front left channel or rear left
> > channel, a noise can be heared on the center channel (and subwoofer, this
> is
> > confirmed pluging a stereo headphone on the center/lfe jack). No noise
> when
> > a sound is played on right channels (front or rear).
> > 2) In alsamixer, if I set the volume to 0 for the front or rear left
> > channels, i can hear the noise on center/lfe when a sound is "played" on
> > this channels
> > 3) In alsamixer, if I mute the front or rear left channels, i can hear no
> > more noise on center/lfe
> >
> > Complementary tests have been made with alsaplayer and using a simple mp3
> > file. In this configuration (stereo output), center and rear channels
> play
> > the same sound as front channel.
> > 1) If all channels are unmuted, I hear no noise.
> > 2) If either the front channel or the rear channel are muted, I can hear
> the
> > noise on center channel.
> >
> > I tried this with alsa-driver 1.0.20 and 1.0.21 with the same result, I
> > recently went back to 1.0.20 due to kernel upgrade.
> >
> > Things that seem strange to me (maybe not so strange to alsa dev :)) :
> > 1) alsamixer shows volumes in percentage, however when I set a channel
> > volume to 50% and the master volume to 50%, I hope to find a resulting
> > volume of 25%, not 0.
> > 2) lspci reports my soundcard subsystem id as 1458:a022, but in
> > /proc/asound/card0/codec#0 the subsystem id is 1458:a002
> >
> > Googling around made me find few references (in alsa-devel list) to a
> > similar problem :
> >
> >
> http://mailman.alsa-project.org/pipermail/alsa-devel/2008-July/008942.html
> >
> http://mailman.alsa-project.org/pipermail/alsa-devel/2008-August/009754.html
> >
> > The distortion / noise described here is exactly what i can hear with my
> > system. Apparently the user solved the issue buying another soundcard.
> I'd
> > like to be sure it is the only way to go.
> >
> > Attached is the file produced by alsa-info.sh
>
> A user had the same issue (Gigabyte P35-DS4), with alsa-info
> http://www.alsa-project.org/db/?f=eb49c36810be2543bcb913d80390f6cba13ec766
> and he just reported back that setting the model line to
>
> options snd-hda-intel model=6stack-dig


> he was able to fix the problem.
>

He tried this on Ubuntu 9.10 (Alsa 1.0.20).
> Assuming that it has not been fixed yet, what change would I make to
> the Alsa source code so that newer versions would be able to
> autodetect the chipset?
> I would appreciate such an answer, as I tend to get a few feedback
> reports on audio cards.
>
> Simos
>

Hi,

I tried the "model" solution, but it did not solve the problem for me.

Playing a bit with "PCM Volume" in alsamixer allows me to give a better
description of what can be heared (very clear when you use "-t sine" option
with speaker-test) :
* the distortion played on center channel looks like the same tone but in
higher octave (that's remind me of harmonics - if the term have any sense in
english), I don't know how to clearly explain the phenomenon, but the center
channel plays a higher frequency than the one played on left channels (front
or rear), few octaves higher (original frequency multiplied by an unknown
factor)

Damien.