Transistor Ladder VCF

Classic Minimoog-style lowpass filter

This is a PCB for a classic Minimoog-style transistor ladder low pass filter in Eurorack format. The main design goal was to make a compact filter (8hp) that is easy and affordable to build. For this reason, front panel controls and main circuitry are integrated on a single PCB, and all components are through-hole (but see build choices in the documentation).

Internally there are a Minimoog-style core and an op-amp output stage. Many thanks to Yves Uson (yusynth.net) for sharing his version of the filter, the core is based on his implementation and was the starting point for me to learn synthesizer DIY. Apart from the obvious frequency and resonance pots, there is a V/Oct CV input (which can track over a few octaves but has rather limited temperature compensation), a CV input with attenuverter, and a Drive control.

Current usage (typical): +12V 20mA, −12V 10mA.

Copyright Caspar Ockeloen-Korppi 2018

https://kassu2000.blogspot.com/2018/07/transistor-ladder-filter.html