On Thu, Oct 29, 2009 at 2:21 PM, Damien Brossard brossard.damien@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) :
- 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.
- If all channels are unmuted, I hear no noise.
- 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 :)) :
- 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