I've got a R. Pi 1 model B+. Tried to attach my USB audio device to it. It's the Behringer 404 (class compliant). Went well of course: I use it w/ my desktop and laptop too. However, as soon as I start Jack and try to do something with it (DAW or something) I loose connection w/ the audio device. I'm convinced that this is a power issue. Because cheap little USB "audio devices" that are as small as a USB memory stick do work w/ Jack and the Pi (link Aliexpress
). A better power adapter for the Pi might work but I think I've already got a reasonable power adapter. Also, the Behringer 404 audio device has got it's own power inlet & adapter and if I use that still no luck w/ Jack and the Pi...
So I wouldn't buy an audio device especially for the Pi if I were you. But if you've got one lying around it's pretty straight forward for us Linuxers to install Raspbian on a Pi and install Rakarrack on it.
Let us know it it worked. Good luck!