After installing Ubuntu and its derivatives on a Dell XPS Studio, the headphone jacks are both unusable. Plugging in earphone to the jack produces no sound, and the system still output the sound on the laptop's speaker.
This problem is confirmed to affect Ubuntu 10.04 (Lucid Lynx), up to the latest version (currently 12.10, Quantal Quetzal)
The problem is related to
alsa. To fix it, follow these steps.
Using your favorite text editor, edit the
/etc/modprobe.d/alsa-base.conf using the root privilege. To edit it with
Gedit, issue the following command
sudo gedit /etc/modprobe.d/alsa-base.conf
Go to the end of the file, and add the following line
options snd-hda-intel model=dell-m6
Save the file and exit your text editor.
Before changes can take effect, the machine need to be restarted.