Thursday, 17 August 2017

My first DIY module

Start small they say.

My first DIY Eurorack module is a simple DC mixer.

I made that choice because I reckon it's easy to build and I found tons of examples on the Net.  It can serve the purpose to mix any type of signals, CV and audio.

Schematic was inspired by Yusynth's with some tips from Ken Stone's and Dintree websites.  It's not much, but you have to start somewhere.

Schematic capture on DIYLC

You'll notice that the first stage is at unity gain and I chose to have the second stage with a 2x gain so that I can use the circuit to boost the signal if need be.

I used DIY Layout Creator (DIYLC for short) to capture the schematic and to trace the layout for a perf board.    Layout is OK, but capturing the schema was a pain.

Layout of the simple mixer : power at the bottom, inputs on the left, outputs on the right..
Warning : the schematic and layout are given for illustration purpose only.  Use them wisely and at your own risk.  Don't forget that I don't really know what I'm doing.

I used a lot of space.  It's a luxury I won't have anymore for the next modules.

I did a mistake though in placing the power connector parallel to the bottom side of the module.  It seemed a good idea at first to have the power lines aligned with the IC.  But once placed into the rack, the flat cable will be crooked.  I didn't respect the de-facto standard to have the -12V at the bottom.  My bad.

Before finalising the cabling, I assembled the mechanical parts to check if all fit.



I  then started with the cabling that did not concern the board : herebelow the input attenuators. 

Cabling pots

I chose to have PCB connectors on the board to ease with the mounting and un-mounting.  I did it on the next module as well.  It takes a lot of space and does not bring so many advantages I think.  My third module will be different.  I'm still undecided on this.

Fully assembled

Here is my first DIY Eurorack module, alongside the A-110-1 VCO and the next one : the Sample & Hold and Random module from the inspiring project from Yves Usson.   The two DIY modules have a temporary annotated paper facade.

The first three


  1. I just built this thing and it works perfectly! Nice clean boost too. But there is an error in the vero layout, VEE isn't connected to pin 4 on the IC so it won't work like that :)
    Thanks for the schematics!

    1. My pleasure. Thanks for the comment. You're 100% right, of course.
      After having used the module for a while, I have to say I'm satisfied, but the chain gain is such that it is very easy to saturate.