Comment 2 for bug 637066

Unfortunately, USB audio devices under Linux are often a pain, because manufacturers don't follow specs properly, so volume information is incorrectly reported. You could try updating your alsa drivers, as outlined here: https://wiki.ubuntu.com/Audio/InstallingLinuxAlsaDriverModules. Note that there may not be a version of this package available for your kernel version just yet, but give it a day, and it will hopefully be available. (I am not responsible for those packages, but I have asked the person who is to get them fixed up.)

If updating drivers doesn't help, then we need to take steps to try and fix the driver in Linux to allow correct volume adjustment.

Please report back as to whether the update helped.

 affects ubuntu/pulseaudio
 status incomplete