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  • Writer's pictureLeonardo

Exploring the new Chorus and SEM filter features in the Freak firmware update

It's been a while since the last update to the Freak module. Initially, I believed version 3.1 would be the final update due to space and power constraints on the microcontroller. However, over the past year, I've been developing a new version of the Vult language (version 1.0). With advancements in the new compiler, I managed to optimize the code slightly, enabling me to incorporate new filter models.

I will talk about the new Vult compiler once I have a release ready. But if you want to explore it, there is a branch in the repository where you can access to it

This new release includes the following new models:


Jorus-II builds upon the module of the same name available for VCV Rack. Originally modeled after the Juno chorus effect, Jorus underwent several changes and enhancements. Jorus (version one) introduced further modifications, potentially making it stand out as an enhanced rendition of the original.

The Jorus-II model integrated into the Freak contains additional improvements. Notably, it incorporates four delay lines per channel, compared to the original chorus which contains only one. These multiple delay lines combine to create a "swarm" effect, generating numerous copies of the input signal.

At a low "swarm" setting, Jorus-II functions like a traditional chorus effect. However, as you increase the intensity of the "swarm," the sound progressively gains density.


The original Oberheim SEM filter had a special mode that mixed its low-pass and high-pass filters to create a unique notch filter effect. Stabile, a filter like the Oberheim, couldn't include this mode in the Freak due to its limited controls.

But now, the new model in the Freak lets you adjust how much of the high-pass and low-pass sounds you want, just like the SEM. The only downside is that the resonance stays the same, and you can only choose fixed levels from 0% to 100% in steps of 10%. If you usually keep the resonance level the same, this could be a good compromise for you.

Improved Flame

The distortion models in Flame had some issues with certain input signals, leading to digital artifacts. The simulation struggled to find a solution quickly enough.

To fix this, I had to do some extra math to find a better way to solve the simulation problem. Now, the distortions in Flame are more efficient and don't create those annoying artifacts anymore.

What to expect next?

From a technical standpoint, I'm gradually shifting gears to replace all the GUI code currently written in Lua with Vult code. This change promises better graphics performance. The main improvement would be eliminating the Lua virtual machine, which consumes resources like RAM and Flash memory. This would free up space for adding new features to the Freak. While I haven't settled on specific additions yet, I do have some ideas in mind.

You can get the new firmware and the updated user manual in the following link:

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