No sound from headphone jack...

Model: Dell Studio XPS 16 - 1647 (reported on 1645)
OS:
Linux Mint 17 - Qiana (64-bit)
Linux Mint 13 - Maya (64-bit)
Linux Mint 10 - Julia
Ubuntu 10.04 - Lucid Lynx

Symptom: no sound when plug-in headphone

Solution:
1) open alsa-base.conf file

$ sudo nano /etc/modprobe.d/alsa-base.conf

2) add the text below to the file (last line)

options snd-hda-intel model=dell-m6

3) restart your machine

Note:
Tested on Ubuntu Lucid Lynx 64-bit.

Update (19/11/2010):
Tested on Linux Mint 10 64-bit.

Update (15/11/2014):
Tested on Linux Mint 17 64-bit.