AMD ALC888 possible solution to distorted sound
 

Hardware;
Biostar 790GX 128M
X2 550BE

Sound is working with Leopard using VoodooHDA. Upon successful SL install sound is distorted. Installed very single voodooHDA kext to no avail.

Today, I thought of installing a sound card to see if it will fix it until I thought of fiddling in the BIOS. I remember an "Azalia" entry somewhere. Found it and disabled it, sound went away. My BIOS has another 790GX HDA entry, I disabled it and enabled Azalia HDA again. Sound came back but still distorted.

I downloaded and installed appleazaliaaudio.kext, reboot, and voila, sound is fixed. So I suggest to check your BIOS if you are having sound issues with your AMD snow leopard.