Aud Calc: Tiny RP2040 Powered Super Sequencer Synth!

At the latest Teardown event, we stumbled upon a remarkable project called the Aud Calc. This nifty little device merges microcontrollers and music in a way that’s sure to excite both electronics hobbyists and music enthusiasts.

The Aud Calc is the brainchild of Jonathan Brodsky, who has successfully bridged the gap between embedded electronics and portable music devices. If you’ve been following Electromaker, it is no secret that we have a soft spot for projects that combine microcontrollers with musical creativity. The Aud Calc is a perfect example, offering features that outshine many commercial pocket samplers. Watch the demo and interview below:

Aud Cal - Background and Inspiration

The idea for the Aud Calc stemmed from a passion for portable music devices like Game Boy music players and pocket operators. Jonathan Brodsky, the mind behind the Aud Calc, wanted more than just what these devices offer. He was eager to build something unique that he could program and customize himself.

Driven by this vision, Jonathan set out to create a pocket-sized sampler that could do much more than its commercial counterparts. Over four years of dedicated work, he developed the Aud Calc. This innovative device reflects his dedication and enthusiasm for blending music with cutting-edge electronics, offering a powerful tool for both communities.

Aud Calc_ Tiny RP2040 Powered Super Sequencer Synth 1

Aud Cal - Features and Capabilities

The Aud Calc is packed with features that make it a standout device for music creation. Here’s a closer look at what it can do:


The sequencer in the Aud Calc is designed to handle everything from synthesizers to samplers and even MIDI output. It supports MIDI sync and CV sync, allowing it to integrate seamlessly with other gear. This means you can create complex patterns and sync them with your existing setup, making the Aud Calc a versatile addition to your music toolkit.

Synthesizer Engines

One of the highlights of the Aud Calc is its synthesizer engines. Thanks to the inclusion of mutable instruments, this device offers a fully featured synth engine that can produce a wide range of sounds. Whether you’re looking to create lush pads or punchy bass lines, the Aud Calc has you covered.


The Aud Calc also excels in sampling capabilities. You can record and manipulate samples directly on the device, giving you the freedom to create unique sounds and rhythms. Its sampling functionality is straightforward yet powerful, making it easy to capture and edit audio on the go.

MIDI Integration

With MIDI in and out, as well as USB MIDI support, the Aud Calc can connect to a variety of external devices. This integration allows you to use the Aud Calc as part of a larger setup, controlling other instruments or being controlled by them. The flexibility of its MIDI capabilities ensures it can fit into almost any music production environment.

Aud Calc_ Tiny RP2040 Powered Super Sequencer Synth

Aud Cal - Technical Specifications

Core Components

At the heart of the Aud Calc is the RP2040 microcontroller from Raspberry Pi. This powerful yet affordable microcontroller handles all the device’s processing needs, making it a reliable choice for this compact synth and sampler. To ensure high-quality audio input and output, the Aud Calc incorporates a robust audio codec. Additionally, it features a 250F Lithium Ion Capacitor, which provides reliable backup power, ensuring your sessions aren’t interrupted unexpectedly.

Additional Features

The Aud Calc is loaded with extra features that enhance its functionality and user experience. It comes with built-in reverb and various synthesizer engines, allowing for a wide range of sound design possibilities. The sequencer includes conditional triggers, re-triggers, and customizable pattern lengths per voice, giving you granular control over your music creation.

Other practical features include a global volume control and multiple MIDI/audio jacks, as noted in the project’s GitHub repository. These additions make the Aud Calc a versatile tool that can adapt to different setups and workflows, whether you’re working in a studio or performing live.

Aud Cal - Development and Challenges

Creating the Aud Calc involved a lot of experimentation and adaptation. The initial prototypes utilized the TEC4 microcontroller, which provided a solid foundation. However, during the global chip shortage, there was a shift to the RP2040 microcontroller from Raspberry Pi. This switch was driven by the RP2040’s availability and its ability to meet the device's requirements.

The commitment to refining the Aud Calc ensured that each iteration was an improvement over the last. By enhancing the sequencer and integrating more robust MIDI and audio capabilities, the boundaries of what the Aud Calc could achieve were continuously pushed. One notable issue involved the device’s buttons. Early versions used standard buttons, which were found to be less durable and prone to breaking. To solve this, there was experimentation with ninja flex clear buttons, resulting in better durability and a more satisfying tactile response.

Aud Cal - Open Source Approach

The development of the Aud Calc embraces open hardware and software principles. This approach aligns with the ethos of the maker community, encouraging collaboration and innovation. By making the design files publicly available, the goal is to inspire others to build upon this work and contribute their own enhancements.

The Aud Calc’s design files are accessible on GitHub, where you can find everything needed to build and customize your own unit. The repository includes firmware, Kicad files for the hardware, and enclosure files, providing a comprehensive resource for anyone interested in this project. Jonathan is active on GitHub and encourages community contributions, welcoming feedback and improvements from fellow makers.

This open-source philosophy ensures that the Aud Calc can evolve through community input, fostering a collaborative environment where ideas and innovations can flourish. Whether you’re looking to tweak the firmware, modify the hardware, or simply learn from the design, the Aud Calc project offers a wealth of resources and opportunities for creative exploration.


Aud Cal - Future Prospects and Availability

The Aud Calc is still in its development stage, with continuous improvements and refinements being made. Although it’s not yet available for commercial release, the progress made so far is promising. The dedication to enhancing the Aud Calc suggests that it could become a commercially available product in the future, offering a powerful tool for musicians and hobbyists alike.

For those interested in following the development of the Aud Calc, Jonathan provides updates and shares his progress on GitHub and Instagram. His GitHub account (jonbro) hosts the project’s design files and allows you to see the latest changes and enhancements. On Instagram, you can find him under the handle jonbro5556, where he posts updates and insights into the project.

Staying connected through these platforms will give you a front-row seat to the ongoing evolution of the Aud Calc, and possibly the opportunity to contribute to its development. As Jonathan continues to refine and expand the capabilities of the Aud Calc, there’s plenty to look forward to in the coming months.

Aud Cal - Final Thoughts

The Aud Calc is a remarkable blend of microcontroller technology and musical creativity, embodying the spirit of innovation that drives the maker community. Its capabilities as a sequencer, synthesizer, and sampler, combined with robust MIDI integration, make it a versatile tool for both musicians and electronics enthusiasts. The use of the RP2040 microcontroller and the incorporation of open-source principles highlight the device's cutting-edge design and community-focused development.

The dedication to this project over the past four years has resulted in a powerful and adaptable device that stands out in the realm of portable music gadgets. The Aud Calc not only offers a unique set of features but also encourages others to explore and expand its potential through open-source collaboration.

As the Aud Calc continues to evolve, it has the potential to make a significant impact on both the music and electronics communities. Its open-source nature invites innovation and creativity, fostering a collaborative environment where new ideas can thrive. Whether you're a musician looking for a compact and powerful tool or an electronics hobbyist eager to dive into a new project, the Aud Calc represents a perfect fusion of technology and art.

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