Systral is a 12hp stereo filter with shared frequency control (but separate resonance
controls) for both channels. It also includes gain pots for adjusting the incoming
signals strength on each channel and this is not to be underestimated since the
incoming signals strength dictates pretty much how this circuit behaves, check out
the Lesja demo on YT for more info.
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It is based on the Korg MS-20 filter but the vision here was to break it down to make
it as dirty as possible. Unstable resonance through red LEDs and a analog noise
source normaled to the CV input was an effort to achieve this. The CV noise is also
audible by turning up the resonance which is by design (and the noise is not (like in
mörser) normaled to the audio path since this sounded so great on its own.
There is a dedicated noise output for making this part available to the rest of your
system and other modules. Making Systral an awesome sound source on its own
being capable or making windy sounds, lasers, and sci-fi landscapes without any
input signals at all (as long as you crank the reconance).
There is a shared blend pot, the dual one, letting the user blend between low and
high pass (rather than having outputs for thes functions it lets just explore the
places between these fitlers).
The left input is also normaled to the right input so you can create a stereo filtered
signal with just one sound source.
It''s a second release out of (more) filthy filters named after 90's Bremen hardcore
bands, the first one was Mörser (also released in 2025).