Eurorack | VocLog

It is mostly sufficient to mix only two or three audio or control voltages together to enhance your sound or the sound animation. So this small mixer comes in handy for mixing CV sources and audio sources as well. This version is DC coupled, so you can use it for AC and DC mixing. There is an inverted output added. You can reverse the DC-CV mix with it or experiment with feedback loops in the audio domain.

Specs and features

Three inputs
Inverted and non- inverted output
Runs on +/-12V and +/-15V
Power consumption below 20mA each rail

The documentation and the Gerber files for download (link) can be found in my website.

**Mixer small: Schematic control board**

This is the Eurorack version of my Sims VCA. This VCA is AC coupled. I made my own implementation of the Sims-VCA introduced by Mike Sims in the EDN Magazine January 1995. With this architecture it is possible to achieve THD of 0,02%. Unfortunately I can not confirm the statement from Mike Sims that trimming the circuit for minimum THD achieves minimum control voltage feedthrough. Trimming for minimum THD causes an constant DC bias at the output. I have had to add a output capacitor to avoid the bias at the output. And you need test equipment to measure the THD for correct trimming. If you can not measure THD better build my DC-VCA. You can achieve 0,2 % THD there. Still good. Or, for Eurorack, my Quad VCA.