FAST AND BULBOUS VCF

VCF / Phaser

this module uses the SSI2140, which is based on the SSM2040 VCF chip, tho with a few updates.
My first thought when I read the datasheets was that it would be great to design a module that could switch between a phaser and a VCF. Looking back at old SSM2040 designs, it seems most of the usual suspects (T. Henry, J. Blacet, C. Anderton et al) had much the same idea.
This module is based on Anderton’s design in Device 1-6 (yes, I spotted the error) with modifications to suit the SSI2140 and Eurorack.
There are 4 switches, one for each OTA stage, to select between (all pass (phaser) and low pass filter mode. You can have quite a lot of fun with 2-3 switches in one mode and 1-2 in the other.
There is a dry mix pot to mix the incoming signals into the OUT signal, which is taken from the 4th OTA stage. This is probably more commonly used in Phaser mode, but there are no rules, so do whatever you like.
POLES is a weighted mix of the outputs of each pole, it is a bit shy when all switches are turned to Low Pass but perks up very nicely when one or more switches turned to Phaser.

https://www.nonlinearcircuits.com/modules/p/fastbulbous