I made this in KiCad, based on the standard op-amp audio mixer circuit detailed by Ray Wilson, Doepfer et al.
Very simple but very useful. All through hole, no SMD.
Can be turned into a CV mixer by bypassing the coupling caps – although swapping the TL op amps for something more precision would probably be a good idea.
Not much else to say about this one – it does what it says on the tin.
I’ve uploaded the KiCad files and the gerbers, so you can make your own if so inclined by sending them to JLCPCB and the like. Feel free to adapt, change, modify or whatever, I don’t mind what you do with it if it’s useful. (creative commons CC BY-SA 3.0).
Click here for the files.