Running Ubuntu on my Dell D830 but had a problem with barely being able to hear the sound. After googling for a while came across:

http://fixunix.com/ubuntu/332757-barely-audible-audio.html

to summarize:
run alsamixer (sudo or as root)
move the front from 80 < > 80 to 100 < > 100 — gnome mixer does not show this.

now works great!