I also have a D600 and whats also strange there is that when I change from ALSA to OSS mixer in the GNOME volume applet, I have a PCM-2 slider which controls the volume of only the headset, not the integrated speakers.
-- [Regression] Master volume does not work when headphones are connected. https://launchpad.net/bugs/26150 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs