MagicQuartz is a microcontroller firmware for the accurate speed control of HiFi record players with AC motor. The highly configurable software can be used for control and signal generation in true sine wave inverters, enabling the implementation of precision turntable speedboxes or motor power supplies.

MagicQuartz aims to perfect the playback speed of vinyl records. It not only offers complete decoupling of a turntable from mains frequency fluctuations, but also electronic switching and adjustment of the turntable’s speed. It is even possible to have the speed continuously monitored and automatically readjusted. MagicQuartz is also a valuable tool for digitizing and archiving shellac records, since non-standard RPM speeds can be set easily.

MagicQuartz has been developed for the 8-bit AVR microcontroller family from Microchip (formerly Atmel). In the context of rapid prototyping, the firmware can also be run directly on Arduino hardware, such as the Arduino Mega 2560 Rev3. To interact with the firmware, an LCD keypad shield or a serial connection via the Arduino’s USB interface can be used.

For a complete list of all features please refer to the documentation.

MagicQuartz is aimed at professional hardware developers from the absolute high-end audio sector, as well as private audio enthusiasts with appropriate knowledge in electronics. An easy to reproduce technology demonstration, the so-called “MagicQuartz TechDemo”, consisting of a fully 3D printable enclosure and an electronic circuit, is available for these target groups under an open source hardware license.

MagicQuartz is a proprietary software that has to be registered and activated. However, thanks to a demo mode it can also be used without registration with minor restrictions (see documentation) for evaluation and hardware development purposes. Since the project is still in a test phase, activations for personal use are currently free of charge. Feel free to send me an e-mail if needed.

Downloads and Ressources

Image above: Rendering of the MagicQuartz TechDemo, created with OpenSCAD.


What initially started as a crazy idea soon developed into the ambitious goal of developing the world’s best speed control for turntables. The project now looks back on over 12 years of passionate research and development (admittedly with major breaks in between):

  • January 2011: First working square wave inverter successfully driving a Dual 1219 at 220V/50Hz (see picture below left).
  • January 2015: Demonstration of a first functional turntable speedbox based on the ATmega328P (see picture below right). A specially developed digital sine wave inverter was used as the inverter.
  • 2021-2022: Further development and porting of the firmware to the ATmega2560 and development of the “MagicQuartz TechDemo” (see above).