This is the only quadraphonic mixer in Eurorack format. You can have an external mixer that outputs in quad, but then the panning will be done in this external mixer and will not be CV controlled. This modules allows you to keep all the quad functions within your Eurorack. It feels to me this is the first building block of a quadraphonic modular synthesizer, but to use it fully, you will need another quadraphonic module like the Aeolus seeds. However with 2 stereo inputs, you can use it with a standard stereo mixer before adding other quadraphonic modules.
With many inputs and outputs close to each others, cable management may be a bit tight, so place this module carefully within your system.
I have 2 of them, so I can have up to 5 quadraphonic voices. This module is really a corner stone of my rack.
Good build, easy to understand, highly recommended.
I have a page listing all the quadraphonic modules on my site.