I installed a sound card which is not detected by my Linux installation, but it is detected and working when I boot off the Live CD. I have tried to do all kinds of things with Alsa to get it to work and haven't been successful. I'm wondering if Alsa can even help with this problem since I'm not sure if it is responsible for detecting sound card hardware.
I've had a similar problem on my laptop. In my case the kernel module for my sound card (Intel, it's the built in one) wasn't correctly identifying my soundcard. I had to supply a hint. That was done in /etc/modprobe.d/
That provided enough hints that the module was able to configure itself correctly for my sound chip.
In your case you need to see what, if any, sound modules are loaded. Cagliostro shows how to do that. Once you've found the card (if there is one), you can then hunt up ways to provide the right hint to your sound module. Finding that 'model' will take some hunting though, and will depend on what sound module is loaded.
No, soundcard (and other) hardware is managed by kernel, and correct modules must be loaded. Maybe livecd loads modules which now are not installed yet.
If you are sure that sound is not muted and alsa is running (
You'll find how to know if your card is recognized and if you have the proper modules loaded.
If they are not loaded you will find how to install the correct linux ubuntu modules package.
For more help you can paste here the output of the following commands: