My stripboard KS-20 filter clone
My modular synth has been in need of a filter for a long time now and a MS-20 VCF clone is an obvious choice loved by many, which is no suprise as it does sound absolutely amazing. However I didn’t find a good stripboard layout online that would fit on the 24-row boards I use so I decided to design my own.
I started out by building René Schmitz’s popular MS-20 clone on a breadboard just to get a better understanding of the circuit and to see that it works. Then I stumbled upon the KS-20 by Kassutronics, which has an added circuit to blend between the low- and highpass modes as well as a drive knob for the input. I added Kassu’s additions to my breadboard circuit, tested them and started working on a stripboard layout in DIYLC.
You can find Kassu’s schematics here.
|R8, R9, R10, R11||220|
|R1, R2, R5, R6, R7, R17||10k|
|R4, R12, R15, R16, R18, R19||100k|
|C5, C6, C8||100n|
|RV1, RV2, RV3, RV4||100k lin|
The changes I made to Kassu’s design:
- Used 2N3906 transistors instead of BC557Cs
- Replaced the 2 TL072s with a single TL074
- Replaced the NE5532 (
U2) with a TL072
- The TL072 can get locked up when driven too hard but I haven’t had any issues with it yet. If you build one and have issues try replacing it with another dual opamp like NE5532 or LM358.
R13with a 2K to get more resonance
- Used purple LEDs instead of green ones
- The purple ones have a bigger forward voltage than green ones so they do alter the sound a bit. I tested a bunch of different LEDs and the difference in sound between them was noticeable but very small.
Here’s the template I used to make the panel: ks20-panel.pdf (0.0 MiB)
Timelapse video of building the module
I took a bunch of pictures with my phone while soldering the module, lined them up in GIMP and converted them to a video with FFmpeg. I think it looks pretty cool.
The finished module
The 14hp panel I made is pretty chonky and the module could have probably fit into 10hp but it looks nice and it’s good to have a bit of space for my fingers.
Here are some clips of me sweeping the frequency knob with increasing amounts of resonance.
Bandpass (LP/HP pot at 50%)
You can find more info on the MS-20 filter and various DIY versions of it at wiki.synthdiy.com.