KA-303 (dev here): a 303 built around a fast acid composing editor

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Hey everyone,

Dev here, so the usual disclaimer applies. Saying it up front so this isn't a stealth plug.

Yes, it's another 303, and I know this forum has a whole thread full of them. So the honest reason I built it: I didn't want another clone. I wanted the real squelch as a base and then a proper writing workflow on top, because that's the part every 303 I owned made painful.

The core is a real 303. Component-level diode-ladder filter with zero-delay feedback, and a square modeled off the way the hardware clips a saw through a single transistor, per-voice drift included. So it reacts like the real thing. I'll let the demo handle that claim.

The composing editor is the part I care about most. The whole point is getting from nothing to a finished acid line in seconds instead of drawing notes one at a time. Scale-locked grid, so wrong notes aren't possible. Drop a few steps or drag in a MIDI file, then let a handful of knobs do the work: Scramble, Mutate, Density, Octave Jumps and a Groove control that shifts the feel from tight to laid back. Slides and accents go straight into the roll. Pattern lengths run 1 to 32 steps, and odd lengths like 3, 5 or 7 drifting against the DAW's 4/4 grid give you that Hardfloor pull that builds and resolves over bars. When you like it, drag the MIDI back into your DAW. Sound presets and pattern presets are separate banks too, so you can leave a line running and click through completely different sounds under it.

There's more under the hood (a Flavor Palette of character engines, four acid distortions with a clean-sub crossover, unison, the usual FX), but it's all on the page and I'd rather you just heard it. Pure sound, no talking:


It's paid, but there's a full demo with no time limit, so the honest move is to just try it in your own DAW. It fades in a bit of noise every 30 seconds and mutes after 30 launches, that's the only catch:
https://kreuzberg-audio.com/en/download ... nthesizer/

If you do run it, I'd like to hear where it falls short, the sound and the filter behaviour especially. And if it's not for you, no hard feelings, there are some solid free 303s around here already.

Cheers,
Frank

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sounds good, can you modulate the settings ?

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Paul_Pulsonix wrote: Wed Jul 01, 2026 8:57 pm sounds good, can you modulate the settings ?
Hey,

thanks a lot for the feedback, really appreciate it!

Just to make sure I get you right: what exactly do you mean by modulating the settings? Are you talking about modulating specific parameters, or something else? A quick example would help me a lot, then I can give you a proper answer.

Cheers,
Frank

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Und det knarrzt, zwitschat und schnattert nur so vor sich hin.
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