A classic MS-20 VCF Clone for Eurorack, in 4HP.
This design is a classic, and many variations can be found across the internet and in many synthesizers and modules. It is based on the late Korg MS-20 VCF schematics which is a variation of the Sallen-Key 2nd-order filter.
(This variation adds a first buffer compared to the original Sallen-Key structure).
The filter can be switched from “Low Pass” to “High Pass” mode.
Documentation
Attention! This project is rather old and needs some adjustments!
External links
Other VCF based on the MS-20 filter:
- http://www.schmitzbits.de/ms20.html
- synthdiy.com wiki
- http://www.analog-synth.de/synths/mod2/ms20filter/ms20filter.htm
- http://www.ericarcher.net/wp-content/uploads/2014/07/9v-analog-diy-lpf.pdf (archived)
- http://www.timstinchcombe.co.uk/synth/MS20_study.pdf
- https://aisynthesis.com/how-to-build-ai004-diy-eurorack-ota-filter-vcf/
Hi David
Could you clarify the schematic for me – I want to make sure I’m reading it correctly. There’s three points within the circuit labelled ‘exp_out’, together with a test point; I’m assuming that these are all common (based off the similarity to René Schmitz’s design).
Hello Steve,
You’re absolutely right, ‘exp_out’ is a *label*, a way to tell KiCad things are connected, but without the need to draw a line.
It’s just a convenient way to not overcharge too much the drawings, particularly here, where the Iabc pins of the OTA are oriented toward the bottom… 🙂
Yep yep! I’m just so used to seeing and using global labels in KiCad that anything that isn’t in a ☖ or ⛉ sort of shape doesn’t register the same to me 🙂