A list of audio interfaces that have been tested with Linux. Hopefully this will help some people answer the question of "does it work on Linux" before spending some money.
USB, 0 inputs, 4 outputs.
USB, 2 inputs, 2 outputs.
USB, 2 inputs, 2 outputs.
USB, 0 inputs, 6 outputs.
http://www.esi-audio.com/products/udj6/
The headphone output is incredibly loud. Turning down the volume with the ALSA mixer lowers the volume but not the noise floor, so you get a very noisy signal not really suited for use with headphones. Would work well for 6 hot signals going into an external mixer or such.
USB, 0 inputs, 4 outputs.
USB, 4 inputs, 4 outputs. Toggleable phono preamps on all inputs.
Set inputs to Phono: $ amixer -c [cardnumber] cset numid=1 0
Set inputs to Line: $ amixer -c [cardnumber] cset numid=1 1
USB, 6 inputs, 6 outputs. Toggleable phono preamps on 4 inputs. Togglable pass-thru on 4 inputs.
PASSTHRU on channel A: $ amixer -c T6 cset numid=1 on/(off)
PASSTHRU on channel B: $ amixer -c T6 cset numid=2 on/(off)
Switch PHONO/LINE on channel A: $ amixer -c T6 cset numid=3 on/(off)
Switch PHONO/LINE on channel B: $ amixer -c T6 cset numid=4 on/(off)
An .asoundrc file making this device present stereo pairs can be found here:
http://www.pogo.org.uk/~mark/linuxdj/t6.asoundrc
USB, 8 inputs, 8 outputs. Toggleable phono preamps on 4 inputs.
Set inputs to Phono: $ amixer -c [cardnumber] cset numid=1 1
Set inputs to Line: $ amixer -c [cardnumber] cset numid=1 0
USB, 4 inputs, 4 outputs. Toggable phono preamps on all 4 inputs.
USB, 10 inputs, 10 output (?). Toggleable phono preamps on 4 inputs.