[alsa-devel] alsamixer - Mute AC97 "PCM Playback Switch" also mute "Master Playback Switch" and "Surround Playback Switch"

Tested on Ubuntu 12.04 and Fedora 17 Live CD

When PA server is running , using alsamixer -c0 to mute AC97 's "PCM Playback Switch" also mute "Master Playback Switch" and "Surround Playback Switch"

but unmute "PCM Playback Switch" does not unmute "Master Playback Switch" and "Surround Playback Switch" of stac9708

alsamixer behave normally when shutdown PA server by

echo "autospwan=off" > .pulse/client.conf and pulseaudio -k

Why pulseaudio server behave in this way ?