MS20-style VCF

MS20 bronze panel image


Controls for the second VCF are a mirror of the first.

Inputs and Outputs

Functions of the second filter's jacks are the same except where noted.

Important Notes

    First off, does this filter sound like the Korg MS20 VCFs? I don't know! I've never had the opportunity to play one. I have heard sound samples of other clones and have built a few other MS20 clone designs, too. They sound tame compared to these two! Though the others may sound "truer" to the original MS20 VCF sound, I find this circuit much more exciting.

    Each module consists of two identical voltage controlled filters. Each VCF is completely independent of the other (except for the RIGHT FM 1 jack, which is make-and-break connected to the LEFT VCF FM 1 jack). The filters can be operated in parallel by mixing their outputs with an external mixer. They can be run in series by patching the output of one to the input of the other. Series connection will give a steeper slope.

    The high pass input is interesting in that it can be used simultaneously with the LP input. Even more interesting is that this jack gives you direct access to one of the filter caps. If you "dummy" plug it, the cutoff frequency will change and the output signal will be boosted. If you then start turning the Res pot clockwise, the oscillations will become very distorted (and loud). Res pot full up and it's a huge, crunchy sound. Tell the guitar player to go home. :)

    One more cool thing, you can influence the cutoff frequency by dummy plugging with a patch cord and then holding the other end in your hand. If you roll your finger (squeeze your hand shut, whatever) across the tip and sleeve you become the "ground" and the cutoff frequency dips down. It doesn't span the whole Freq range, but it can be used effectively to add a little (literal) "human" touch.

I can etch an adapter board for users (tell me when ordering).

MS20 PCB, bronze panel image

Sound Samples

    These audio samples are, for the most part, unedited. Long, too! They can get a little tedious but I'm hoping you patch heads will give me a little slack. They do show off some of the many flavors this filter can produce.

    Most of the samples are simply a VCO patched into the MS20 module. Modulation is supplied by LFOs, envelopes and my hand. These samples exploit and show off the resonance characteristics of the VCF. It can also sound very smooth and transparent when the resonance pot is kept under 11 o'clock. In fact, they work well as utilitarian lowpass or highpass 2 pole filters when the RES is at minimum.

    I'll get some low resonance samples up, if needed.

MS20 bronze panel closeup image

Return to the top.