Traktor Audio 2

The original version of the Native Instruments Traktor Audio 2 (the one with two 1/4 inch/6.35 mm jacks; the one with 1/8" inch/3.5mm jacks is the newer model) can work with Mixxx on Linux but it needs a bit of configuration. This device presents to ALSA as two subdevices, but by default PortAudio, the cross-platform library Mixxx uses to access sound hardware, only lists one of the subdevices in Mixxx so the headphone output can't be configured. To work around this, copy and paste the text below to a file at ~/.asoundrc. Select "TraktorAudio2Master" with Channels 1-2 for Mixxx's Master output and "TraktorAudio2Headphones" with channels 1-2 for Mixxx's Headphones output:

pcm.TraktorAudio2Master { type plug; slave.pcm "hw:TraktorAudio2,0,0"; }
pcm.TraktorAudio2Headphones { type plug; slave.pcm "hw:TraktorAudio2,0,1"; }