I was looking for a DIY project to work on during lockdown and thought a little passive mixer for my eurorack could be cool. I needed a way to mix the 3 voices from my STO module and maybe split the result into 2 outputs so I can send a copy of the signal off for further processing. I had a search online but couldn’t find a simple plan for what i was wanting to do. So I created this based on a few different schematics.

I built mine from spare parts that I had lying around so 2 of the potentiometers are B10K. I would recommend using A10K as the audio comes through a little louder. I managed to desolder the three 1K resistors from other unused and broken projects.

I also thought it would be a good opportunity to learn Autodesk Fusion 360 some more so decided to design my own panel that could be 3D printed. You can download an STL and 3MF file here if you would like to 3D print your own. Just ensure the height is 128mm before you print.

It was a little bit tricky to solder in some parts as I was trying to keep the back as clean as possible, the result works well and the fact it is passive means no power issues! A great simple DIY project to cut your teeth with.

Posted in DIY
Posted by:Scott

Audio/visual artist based in New Zealand.

6 thoughts on “ DIY Passive Audio Mixer ”

  1. I’m looking to do the same, but I only have a bunge of B1K pots laying around. It seems to work but I don’t know what kind of resistors I need to put behind them, I’ve a large set of values I bought for an other project. Any tips?

    1. Hey, I would experiment and see what works the best. I found my circuit worked great with an audio signal from my phone but it doesn’t work so well with the very hot signal from my modular synthesizer, so I will probably try some different resistors to see what works too.

  2. Thank you so much for sharing this schematic. I used B10K pots for this – they’ll work in a pinch – and will definitely order some A10K for future builds. I amended the above diagram by tacking on a momentary button (one between the tip & pot) for added cutup capability. It’s a blast!! Cheers!!

  3. I have the Problem that if i send a Signal to CHl 1 the Potentiometers of CH 2 & 3 affect te Signal of CH1. If i close CH2 and/or CH3 the Signal of CH1 also get muted.

    1. Exactly , this is because when you put to zero an input all the active signal inputs Will be grounded by 1K resistor of the zero level input.

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