https://bugs.launchpad.net/ubuntu/+source/alsa-driver/+bug/581650

...

Master ranges from -46.5dB to 0dB but PCM ranges from -34.5dB to +12dB,

Daniel T Chen https://launchpad.net/%7Ecrimsun wrote on 2010-05-18: #1https://bugs.launchpad.net/ubuntu/+source/alsa-driver/+bug/581650/comments/1 This is not a pulse bug but a hardware one

I wonder why you said this is a hardware bug since this is ac97 specification

maximum the total gain will be +12dB, not 0dB as indicated.

Did you read those ac97 2.x specification ?