S/PDIF Input won't play(Fender Mustang Micro plugged in via USB)?

Trying to get a fender mustang micro(head phone amp for a guitar) to plug into my Ubuntu 20.04.2 LTS laptop. So the setup is the mustang micro is plugged into my guitar, the mustang micro has a USB cable connecting to my laptop, and my laptop is plugged into a stereo amplifier via a standard 1/8" audio cable(head phone jack).

If I open the settings and go to sound, the output device is set to "Headphones - Built-In Audio" and if I use the test button both left and right speakers connected to my amplifier play the sound correctly. So audio out is working.

For the input device I have selected "Digital Input (S/PDIF) - Fender Mustang Micros". If I strum the guitar the little red bars directly below it light up indicating that sound is coming through, but no sound is played through the speakers. PC volume, Amp volume, mustang micro volume, and guitar volume are all turned up, but 0 sound is played. The sound app in setting's is getting the audio, so something appears to be amuck with getting the signal from S/PDIF to the audio output device. I've also tried turning up the volume on everything in alsamixer and it still doesn't work.

Here's a screenshot of the sound settings while I'm strumming the guitar, the red bars under the inpute device drop down move when I'm playing and stop when I mute the strings. Test button for headphones works too.

Any idea why the sound isn't making it out to the speakers?

1 Answer

Usually there is an application of some type used between the input signals and the output signals of the audio subsystems of the computer. This can be something as simple as

arecord -t wav | aplay -t wav

which should pull a wav type stream from the standard input to the standard output.

More complex solutions provide possibilities to do many other things. Using Audacity one could get the input signal, record it, apply effects to the sound, and play it back. More complex applications might involve jack to route the sound signal through the computer, and a DAW sign as Ardour or LMMS to process the sound signal.