Here is a short note on the steps I had to take to make Ubuntustudio (You can either do a fresh install from the Ubuntustudio-DVD or by installing the relevant additional packages in a running Ubuntu installation)
First important thing was to add the following lines to /etc/security/limits.conf:
@audio - rtprio 90
@audio - nice -10
@audio - memlock unlimited
For that to work the local user has to be added to the group audio (if he/she isn’t already a member):
$sudo adduser [username] audio
Next thing was to get the external soundcard to work. I was lucky: I have a Maya 44 USB which runs out of the box (though I would not recommend this soundcard for other reasons). For other soundcards the ALSA compatibilty matrix or the FFADO device support list should be checked.
Then the automatic configuration script asoundconf has to be run. There is also a little GUI for System->Preferences for this task which can be installed with the package asoundconf-gtk.
Afterwards, in System->Preferences->Audio I switched everything to ALSA.
The volumes of the input and output channels of the soundcard can either be controlled with the tool alsamixer or by double-clicking on the loudspeaker-symbol (at least in Gnome).
There were also some problems with ALSA and Pulseaudio which resulted in no sound when using ALSA. I “solved” this by deinstalling every package that had to do with pulseaudio. Afterwards everything worked fine.
In the Jack Control tool you just have to make sure that you choose the right interface. At first, I didn’t get that it is also possible to click on the “>” to get some more information which device “hw:0″ actually is. The settings for Frames/Period and the Periods/Buffer have to be experimented with a bit to find a stable configuration with an acceptable latency.
