Plugging in an USB sound card to a linux machine can be quite frustrating because it does not become the default device automatically. Today I read about such an option in alsa that I didn’t know about before.

All you have to do is to open the /etc/modprobe.d/alsa-base.conf as root and toggle out a line.

Looks for this section…

# Keep snd-usb-audio from beeing loaded as first soundcard
options snd-usb-audio index=-2

…and make it look like this:

# Keep snd-usb-audio from beeing loaded as first soundcard
# options snd-usb-audio index=-2

After a reboot your USB sound card is the default card for alsa when plugged in.