not sure what changed, but when I upgraded to ubuntu 11.10 my laptop (acer aspire 3050) started to get problems with my headphones.
now when I put headphones in is that the sound comes out of both the headphones and the laptop speakers, and that sound levels reset to maximum when I restart the laptop.
I can turn off the speakers using alsamixer.
I have also tried changing the settings in /etc/modprobe.d/alsa-base.conf but no joy so far.
Best Answer
I had no sound coming through my headphones until I switched the output to Analog Speakers. Now it's fine.