Paste your alsaconf maybe someone can see if something is off.
Are you getting no sound at all from everything; no system, no application, and no internet sound?
You have the drivers installed?
You have alsa enabled as the audio device in the sound system settings?
Is it a new sound card? Maybe you have to uninstall your drivers and reinstall them. It was like that in windows when switching anytype of card with another.
I'm still new to linux and I don't know much but I will help where I can. Just google and you should also find a solution. I've had some big help with my problems googling it just take some time. You can also read up at http://alsa.opensrc.org/index.php?page=asym
for some more help.