I’ve written posts before on how to get audacity to work on Ubuntu.  I went through a lot of trouble with getting it to record audio streaming from the internet a long time ago.  I had to get alsa running, and then make sure that the browser was running first, etc.  It was way too much of a hasle to go through, but luckily I found a way to easily do this.  I’m on Ubuntu 8.04, but there is also a way to do this with KDE.  You can find more info about that here.

When you try to record the output from your soundcard, audacity will probably give you some sort of error.  That is what it did with me.  I tried changing the recording properties to alsa, but I had no luck with that.  What you need to do is right click on the volume icon on your panel and select “Open Volume Control.”  Then, under the Edit menu, select Preferences.  Then check Mix and Mix Mono.  Take a look at the screenshot above.  Now close out of that window and go to the switches tab in the volume control window.  Make sure that you check Mix or Mix Mono under there (screenshot below).  Now when you try to record output from your soundcard in Audacity, it will work.

This is a much better way to record soundcard output with Audacity than the way I had been using.  Let me know if this works or doesn’t work in the comments.