NVIDIA ION + Ubuntu 10.04 Lucid Lynx + 5.1 sound analog output

1. Edit alsa-base.conf:
sudo gedit /etc/modprobe.d/alsa-base.conf
2. Add the following line to it:
options snd-hda-intel model=3stack-6ch enable=1 index=0
3. Reboot. The 5.1 channels would be enabled so that alsamixer could be used to unmute them. Enjoy! Credit: Pascal's blog