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I'm running Ubuntu 9.04. Worked fine for months, then I rebooted yesterday after weeks of continuous operation. Now audio won't play through the speakers. The USB headset works fine, but the Conexant audio (CX20549) does not. Weirdly, it thinks it's playing. pavumeter shows appropriate levels, volume looks OK in alsamixer, but no sound.

I did find this page:

Unfortunately the advice there doesn't help me. For one thing, the syntax for the alsa-base.conf file is apparently not actually documented anywhere. For another, my chipset isn't listed in the docs he links to!

EDIT: would upgrading to 9.10 help? Is there a major change in the audio subsystem between 9.04 and 9.10? Any suggestions?

EDIT 2: This is stranger than I thought. Sound works normally in Xine, but is silent in Audacity, VLC and mplayer. What the?

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the link you're talking about is using modprobe-style options (like the ones found in /etc/modprobe.d/* ..). you may also look into tweaks in a .asoundrc: – quack quixote Nov 9 '09 at 0:30
up vote 1 down vote accepted

Audio using PulseAudio is very buggy by default in 9.04. It is improved in 9.10, but there are still issues.

You can try to solve it following this recommendations:

Also, it is worth considering Kubuntu, which doesn't use PulseAudio by default (this is true for the latest versions of Kubuntu).

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I ended up upgrading to 9.10 (which I would have done soon anyway) and sound is working now. I will keep your suggestions and Quack's in mind should the problem return. – CarlF Nov 9 '09 at 1:14

Check the mixer settings.

For some reason it sometimes it goes to zero after a reboot (on some Ubuntu installations).

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First thing I tried. Those settings are fine. – CarlF Nov 7 '09 at 18:38

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