Connect OP-Z

Connect OP-Z as an audio device on norns.

This norns program has a single purpose, namely to connect monone norns to teenage engineering OP-Z audio over USB for both input and output.

I hope to improve my setup in the following regards:

1. Audio signal from OP-Z headphones to norns input is weak and loses in quality when driving OP-Z at full volume. USB audio has more umph
2. OP-Z reserves the audio in jack of norns shield.
3. Less is more.

WARNING: Do not disconnect or turn off the OP-Z when it has been connected as an audio device with this program. This will leave processes running wild on the norns, and will produce loud digital noise.

https://llllllll.co/t/using-usb-audio-with-norns-case-op-z/

Requirements

• norns
• teenage engineering OP-Z

Purpose

The following storyline illustrates the ambition, and success of this program.

Original setup in which I have monome norns shield running on a Raspberry Pi 3+ powered by a battery pack. Etymōtic ER2XR headphones are connected to norns output, and OP-Z is connected both with a USB cable for MIDI and with an audio cable for audio from OP-Z to norns.

In a simplified setup the USB cable which I'll use anyway also transport audio both ways, removing the audio cable from the setup and also adding sound from norns to OP-Z.

An extended setup, now that the norns audio input is free for using with a PO-28 Robot, PO-16 Factory or smartphone running YouTube, SoundCloud, browser, Spotify, software synths like nanoloop and Caustic, messaging apps etc. fun sound sources.

Function

The way this program works is that is runs alsa_in and alsa_out for the connected OP-Z, and routes them softcut and crone in jack. This manipulates the audio stack under norns, which remains ignorant of these changes.

Enabling input from OP-Z to norns and output from norns to OP-Z are controlled separately.

Further ideas

It would make sense to do this at system level rather than a norns program. This would be done by adding udev rule in /etc/udev/rules.d plus writing a program which starts alsa_in and alsa_out when the OP-Z is plugged in and adds the jack routes, and tears this setup down when the OP-Z is disconnected from USB.

Another idea would be to amend the norns systemd service norns-jackd which is defined in file /etc/systemd/system/norns-jack.service.

It might be worth looking at alternatives to alsa_in and alsa_out, Jack 2 might have something for this.

Last idea would be to get a hardware mixer, rather then user norns as my mixer.