Comment 7 for bug 992644

Re #3: I encounter the same exact behaviour on a freshly acquired Samsung Chronos 7 700Z5C, on a freshly burnt 12.04 amd64 iso install. Aumix seems to be the only way out of this for me as well, and I do see, as you, the speaker volume being muted.

However, I'd like to add that plugging the headphones again does not cure the problem. While it restores the headphones' volume to their previous level, speaker volume will remain muted, and then only aumix can help -- which needs snx-mixer-oss to be modprobed, BTW.