Comment 28 for bug 363892

I don't believe that I ever manually touched the lines in /etc/modprobe.d/lanai-sound, and have gone from the stock Hardy that my 1420 shipped with to Jaunty. I saw the same problems, and /etc/modprobe.d/lanai-sound contained model=3stack when I looked.

Quick summary of behavior I saw on my 1420:

model=3stack (what was in here when I first ran across it): no sound in Jaunty

(delete line -- based on Daniel T Chen's text above, this is equivalent to specifying dell-bios): sound is present on external speakers w/o problems, but about a quarter-second after plugging headphones into headphones jack #1, the sound on the headphones (which is fine for a quarter-second) is muted -- external speakers are also muted.

model=dell-3stack: Everything works properly

Based on this, I would guess that the proper workaround for a 1420 (unless there are multiple revisions of this model 1420 that require different settings) is:

* Go to /etc/modprobe.d/lanai-sound

* Remove any existing lines beginning with "options snd-hda-intel"

* Add a line that reads "options snd-hda-intel model=dell-3stack"

* Reboot