Available as an assembled Module and as a DIY project.
This Module is discontinued.
Dual Mixer/Averager
Dual mixer is a dual Averager.
Each on of the 3 inputs have a gain of 1/3 of the output.
Unlike Unity gain mixer, Averager avoid clipping, so it's particularly suitable for rapidly mixing audio sources such as oscillators.
It can also be use as a precision attenuator/mixer.
https://blacknoisemodular.com/products/black-noise-dual-mixer-eurorack-module