A diagram of the Korg-35 IC, the source of the original MS-10 and MS-20 filter's iconic overdriven sound. It's essentially a VCA that causes the Sallen-Key filters to overdrive at the cost of a drastic bass cut. It was produced in an 8 pin SIP but was eventually replaced with an LM13700 OTA based VCA due (as far as I'm aware) to the cost of producing proprietary ICs. The LM13700 version has its own charm (and frankly more stability), but it cannot recreate the angry hiss that defines the original MS-20 filter.
Pinout:
1 connects to 47K
2 connects to 680R
3 connects to hanging NPN collector
4 connects to emitter/collector pair
5 connects to JFET gate/NPN emitter
6 connects to 10K by JFET drain
7 connects to 820R
8 connects to 10K and PNP emitter
All NPNs are 2SC1623
PNP is 2SA812
The MOSFET is actually a 2SK94 JFET, but this program does not currently support JFETs
The circuit on the right is supposed to be the test circuit for the Korg-35, see the original notes for more details. They can be found on Tim Stinchcombe's excellent website, but note (as Tim himself states) that this should be used for educational purposes only, as it remains proprietary Korg technology.
