The Pi comes configured to use the on-board sound system by default. This a problem for those that want to use the higher quality or stereo in and out available from an external USB soundcard.

The solution is to change the configuration so that a USB soundcard becomes the default sound system, when present.

Here’s a step-by-step guide to make the change:

1. Open a command line terminal
2. Type: ‘sudo nano /etc/modprobe.d/alsa-base.conf’ This will open the sound system config file in the nano editor
3. Find this line: ‘options snd-usb-audio index=-2’
4. Change it so the last part reads: ‘index=0’
5. Add the following on the next line:  ‘options snd_bcm2835 index=1’
6.  Press ctl x followed by Y then Return to save the changes and close the editor.
7. Type ‘sudo reboot’ to reboot the Pi

With a bit of luck you should find that your USB audio card is now the default sound device for applications such as SonicPi, etc.