[alsa-devel] Strange findings about the microphone in SigmaTel STAC9221 A1

My hda-intel card is with the following codec:

Codec: SigmaTel STAC9221 A1 Address: 0 Vendor Id: 0x83847680 Subsystem Id: 0x106b1700 Revision Id: 0x103401

I am using alsa 1.0.14rc4. I have a built-in microphone, which doesn't work, but today I found out something interesting. If I set the capture to minimum and place Mux at specific positions (Works with middle-ish and top, not bottom-ish) suddenly the mic started recording, but the quality is extremly bad. I have attached amixer and co. Does anyone have a clue what the issue is and how could possibly this little bit of random foundings to be used to possibly fix the mic?

Regards.