Listen IO

Stereo input/output interface for use with external equipment

The Listen IO is a simple module to convert signals to and from normal Eurorack modular levels.

The top section converts any external signal to Eurorack signals by providing up to 30x gain (+30dB). Table-top synths, keyboards, phones/tablets, computers, toys, microphones, etc.. You can even patch quiet modular signals into the top section to provide additional boost.
A stereo signal, or two mono signals (such as two microphones) can be plugged into the Line In jacks.
Turn the Gain knob and watch the LED lights. The top light indicates clipping, and the other three indicate signal strength. Now you can patch the Mod Out jacks to any Eurorack module.

The bottom section is the opposite of the top: it converts modular signals to Line-level and/or headphone level signals. Simply patch your modular signal (stereo or two mono signals) into the Mod In jack, and adjust the Level knob as desired.
The bottom two jacks can be used as headphone jacks, so you and a friend can listen at the same time! The left jack is L/R and the right jack is R/L (the left and right channels are swapped).
You can use the bottom jacks for Line out. Either a stereo or a mono cable will work. You can even use one jack for headphones and the other jack to run a stereo or mono signal to another piece of equipment!

https://4mscompany.com/listenio.php