A modular hardware design combines RP2040 microcontrollers with the AS3397 analog voice chip to deliver an affordable, expandable polyphonic synthesiser.
A team of researchers has developed a new analog synthesiser named PolyUAnalog, which is an open-source module-based polyphonic analog synthesiser based on the AS3397 analogue voice chip and RP2040 microcontrollers to build an affordable, expandable synthesiser. The design is aimed at researchers, students, and hobbyists who are interested in building or modifying analog synthesisers.
Each voice of the synthesiser is independently driven by a dedicated RP2040 microcontroller while a conductor board handles the MIDI interface, system management, and I2C communication. The circuit avoids using expensive digital-to-analog converters (DACs) through filtered PWM signals. Moreover, a PI control loop in real-time is used to regulate DCOs to ensure accurate pitch for all voices.
This modular system supports digital effects, wireless browser-based controls, multiple MIDI interfaces, and expandable voice cards.
A number of input options can be used on the synthesiser, such as traditional MIDI inputs, USB and wireless connections, while digital effects and web-based configuration capabilities increase its potential. The modular design of the synthesiser makes it possible to include extra voice modules, thus allowing the user to change the synthesiser’s configuration from monophonic to polyphonic by adding additional voice modules without redesigning the base synthesiser.
According to the authors, the electronics for an eight-voice synthesiser will cost less than €200.
