Available as an assembled Module and as a DIY project.
This Module is currently available.
Three Channel Mixer, w/ Output Attenuator
Three-channel audio mixer
MIX is designed primarily for clean, high-quality audio mixing. It is fully DC-coupled, though, and so retains the ability to be used as a CV mixer when necessary. Under the hood it's a basic unity-gain op amp mixer, with three unipolar inputs and an output which can be switched between uni- and bi-polar operation using a jumper on the PCB. The inputs use audio-tapered controls while the output is linear to facilitate both modes of operation.
A great deal of testing went into the selection of the components used to ensure the lowest possible noise, absolutely minimal cross-channel bleed, and as little added "color" as possible.
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These merchants probably sell this module. Huh?