Ubuntu – How to set a default audio output device in Ubuntu 18.04

In order to change the default audio output device from the command line, you can use the pacmd Pulse Audio command-line utility.

I found the need to do similarly today, wanting to switch between headphones and speakers, both plugged into separate audio cards. Here's the shell script I wrote to do so:

#!/usr/bin/env bash

sinks=($(pacmd list-sinks | grep index | \
    awk '{ if ($1 == "*") print "1",$3; else print "0",$2 }'))
inputs=($(pacmd list-sink-inputs | grep index | awk '{print $2}'))

[[ ${sinks[0]} = 0 ]] && swap=${sinks[1]} || swap=${sinks[3]}

pacmd set-default-sink $swap &> /dev/null
for i in ${inputs[*]}; do pacmd move-sink-input $i $swap &> /dev/null; done

Notes:

• This swaps between the first two audio output devices that the pacmd utility lists. If you have more than two audio devices and want to swap to a different one, you'll need to replace the logic on line 7 with some conditionals.
• Just swapping the default sink device does not do anything for the applications currently running — they will continue to output to the previous device. This script also moves the sink destination for all existing inputs. I.e., if you run this script with music playing on one device, it will instantly swap to the other. If you'd like the existing applications to continue on the previous device, comment out the last line (and line 5, if you'd like).

pavucontrol

For a much better fine-tuning of our default audio setup we may install and run pavucontrol which also has an option to set a fallback device (below shown for a bluetooth headset):

If this does not work as expected you may have an issue with the module-switch-on-port-available loaded from the default.pa settings. You may try to disable this module.