[alsa-devel] Sound distortion with Realtek ALC889A

[Damien Brossard]

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

Thanks in advance.

Best regards
Damien Brossard
-------------- next part --------------
A non-text attachment was scrubbed...
Name: alsa-info-output
Type: application/octet-stream
Size: 14258 bytes
Desc: not available
Url : http://mailman.alsa-project.org/pipermail/alsa-devel/attachments/20091029/cfe3e2f6/attachment-0001.dll