PCB for Eurorack 4x4 active matrix mixer

PCB for a 4x4 active matrix mixer

This is a companion module to the passive matrix mixer  but is rather more versatile on account of it being active _and_ having a gain control on each of the four channels. If you're a full-on noisemonger then this gives you the chance to get some juicy feedback going if that's your idea of a good time.

The board has four sets of pads which allow you to either resistively or capacitively couple the inputs - if you're after mixer feedback then I recommend using 100nF capacitors since removal of the DC offset will minimise the risk of the op-amp latching up.

If you're not clear on how a matrix mixer works then Wikipedia actually has a decent article on the subject - basically you can route multiple sources to multiple destinations and each can have it's own mix, hence all the pots. Signal routing can be immensely confusing to begin with, and the best way to understand it is to refer to the schematic.

100% through-hole components and an ideal beginners project - the BOM and schematic can be found here: https://bitbucket.org/yorkmodular/matrix-mixers/src/master/ - I recommend the use of Alpha 9mm pots, since these will afford a greater degree of support to the panel.