From MakerVan Labs

Revision as of 19:04, 19 March 2021 by Severin (talk | contribs) (missed the amounts on the pots)
MatrixMix 4x4

Release status: beta [box doku]

Description A simple yet extendable matrix mixer
Last Version  0.2 (2021-02-17)
Download  GitHub Repo

A simple passive 4x4 matrix mixer. Extendable, and with sync passthrough.


  • 4 Inputs
  • 4 Outputs
  • Extension ports so extend the mixer to many more inputs, or add buffers/amplifiers to the outputs
  • Sync passthrough, to support sync signals on the audio jack, like in Teenage Engineering Pocket Operator synths. Selectable on each input/output

Note: This is a passive mixer. So when you change one knob, there might be changes of loudness for the other channels as well. There’s no buffering between the channels, so it’s completely normal like that.



Part of Circuit Part Number Distributor Amount Notes
Potentiometer (50kΩ lin) Bourns PTV09A-4020S-B503 DigiKey
16 Suggested for v0.1
Potentiometer (50kΩ log) Bourns PTV09A-4020S-A503 DigiKey
16 Suggested for v0.2
3.5mm jacks EBSF 35
Resistors 10kΩ reichelt

You can populate P1-P8 with 3-pin 2.54mm headers, and mix the two channels of a stereo plug together, or pipe the second channel through to other devices, in a mode compatible with the Pocket Operator synths or similar modules.

Connectors P9 and P10 can be used to connect multiple MatrixMix 4x4 boards together to create a matrix mixer with 8, 12 or even more inputs.



This is an early prototype version of the MatrixMix 4x4 PCB. As such, it has one fun error in it: All potentiometers are backwards. So you have to turn each knob counterclockwise to make things louder. It’s a little unusual, but also kind of fun. Note though, that normally you would use logarithmic pots for audio signal. When soldering the PCB as is, this does not make much sense. So use linear pots instead (There are reverse logarithmic pots, but they are hard to come by).

One alternative is to flip the board upside down and solder the pots from the back side. That works quite well, just your inputs are now on the bottom (or your outputs on the left, depending on your flip). Make sure to solder the 3.5mm jacks in as originally intended, otherwise the sync-passthrough does not work anymore.

  • Potentiometers are wired the wrong way, they all turn the wrong way
  • 10k Pots and 10k mixing resistors don't turn things all the way down


Potentiometer orientation is fixed, and with proper values (50kΩ pots + 10kΩ mixing resistors) this thing is lots of fun.