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  • Writer's pictureLeonardo

More prototypes, more Freaks

Updated: Nov 2, 2023

When I started my Eurorack journey, I made a deliberate choice to design the majority of modules for my rack myself. The motivation was that, by designing the modules, I would force myself to learn more about the electronics applied to synthesizers. While purchasing ready-made modules from third-party vendors is convenient, it can be expensive. On the other hand, developing my own modules incurs higher costs than purchasing ready-made modules and the design process is complicated. Nevertheless, the satisfaction and fulfillment I derive from creating my own modules far outweigh these challenges.

Over the past few months, I have been actively engaged in research and development, which has led to the creation of several module designs. Among these designs, some have great potential to be transformed into marketable products, while others will remain in the prototyping phase or are one-off modules for me. The process of designing, building, testing, and refining these modules is time-consuming, taking away from the time I could spend on assembling other modules, such as the Freak filters.

I would like to feel that the effort I invested in R&D has been worthwhile. Therefore, I would like to share with you two modules that are nearing completion. These modules are on the brink of being finalized, and I am excited to showcase them.


I have been working on Caudal for almost three years (non-continuously). My current revision is 3.1. This is my third time creating the entire design from scratch.

Vult Caudal Prototype

The initial version of the module had a flaw, and due to over-designing, it would have ended up being too expensive. I documented this experience in a blog post.

For my second version, I opted to base the design on the Teensy 4.0 board, as it was readily available during the initial stages of the semiconductor shortage. However, by the time I completed the design, it became impossible to purchase the Teensy boards.

Caudal v2 using a Teensy 4.0 (not the final design)

In the third iteration, I decided to eliminate the Teensy altogether and instead rely on my own board design as the central processing unit.

Caudal v3 removing the Teensy.

As you can see in the picture of the module, Caudal provides 8 outputs instead of the 12 available in the VCV Rack module. By removing the "angle" outputs, I was able to add S&H functionality. In addition to the three modes available in the VCV Rack version (Pendula, Planets, and Fish) I will be adding some extra operating modes. To give you a hint, the words "Uncertainty", "Fluctuating", and "Turing" may sound familiar.

Caudal is working, but I still need to develop the firmware upgrade procedure. Once the module can be upgraded, I will be sending some modules to testers.


Another module that I developed is Vermifuge a new analog filter. Some months ago, I shipped the last assembled Vorg and I decided to discontinue it. I planned to redesign it (for the third time) using SMD components. While doing that, I thought it would be a good idea to add some extra features. The result was so different that I decided to make it a new module: Vermifuge.

Vult Vermifuge. A new multi-form analog filter.

Vermigue contains a Vorg filter in addition to a ladder and state-variable filter. Vorg and the state variable filter include three configurations: LP, BP, and HP. The ladder filter includes only an LP filter. Here is a picture of the initial prototype.

Vermifuge initial prototype using a bunch of custom modules.

Vermifuge is a nice filter, but being 100% analog, it is hard to tweak it and make it sound exactly as I want it to sound. It still needs some work. If you think you need a filter like this, please let me know so I can motivate myself to take it out of the prototyping stage.

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