How To Use Multiple Audio Interfaces With Linux Using Jack and Qjackctl

This is a very valuable technique for using multiple audio interfaces in Linux for expanding your audio inputs for multitrack recording. For example, say you only have a 4 channel usb interface but need 6 mics to record drums. Or what if you want to run to multiple audio device outputs for a DJ setup? This technique will allow you to achieve both of those!

The first thing you’ll want to do is have all of the interfaces connected you plan on using, then start up Qjackctl using one of the interfaces (usually your main interface). After that is up and running, open up terminal and type the following command:

cat /proc/asound/cards

This will list all of your currently attached audio devices according to Alsa.

Take note of the numbers on the left (outlined in red in the image) and their corresponding audio devices.

Now that you know which number corresponds to the secondary card you want to use, you can use to to create additional inputs or outputs or both by using the alsa_in command. To add an audio input using card 1, enter the following command:

alsa_in -d hw:1

Then you’ll magically see a new input in Qjackctl called alsa_in!

To add an output is nearly the same, just do:

alsa_out -d hw:1

To see a video example of this, watch below!

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