Enable 5.1 Sound in Backtrack 5 r3 and Ubuntu 10.04

Open Terminal and Enter the following line

sudo gedit /etc/modprobe.d/alsa-base.conf

Add the following line to the file

options snd-hda-intel model=3stack-6ch enable=1 index=0

Now Reboot your computer and open "alsamixer" by entering it into the terminal and unmute the Center & Surround Speakers.

That's it! Enjoy your 5.1 Surround Sound :)