KORG: MS-20 Filter - Rene Schmitz Version

This is the Rene Schmitz version of the MS-20 Filter, which is used in the later models.  I didn't include the CV control inputs, as I have no plans on using CV.

KORG MS-20 FILTER - VERO LAYOUT

KORG MS-20 FILTER - BUILD REPORT

This is a very particular sound, and while it doesn't have a lot of uses, it does do a screaming filter sound really well, and can go into oscillation.  It would be more useful with the frequency control running off an expression pedal - or in a synthesiser where it belongs...   

I would firmly recommend adding a volume control at the end, as this can really pump out some level, and/or do not place it in front of anything that is going to die if you feed it high input signal. 

Adding a single germanium diode to the pair of green LEDs or replacing a LED with germanium made a massive difference - I recommend trying this, as it tamed the beast somewhat.  Could pop it on a switch easily enough.  

I also added a 1uf on the input, as the original doesn't have a coupling cap, and I increased the output cap from 470n to 1uf, just because that's what I had on the input.  I have large 1uf caps on the layout, but I decided to use multi-layer ceramics to keep the size down.   The layout is quite flat, basically nothing is higher than the ICs.

Voltages are running at around +/- 17v instead of +/- 15v as that's the best I could do with the MAX1044.  I didn't exactly put in a lot of time trying either.

Note:  diodes and a 10k resistor are on the breadboard