Jan 9, 2026 | Dominic Fox
Vulpus Labs demonstrates their Voltage Modular sound engine module that imitates the audio behavior of the 1982 Sinclair ZX Spectrum 8-bit home computer.
RKW-2 is an homage to the pioneering work of Tim Follin, who achieved extraordinary things with the beeper of the Sinclair ZX Spectrum. RKW-2, a Voltage Modular module from Vulpus Labs, emulates ZX Spectrum 1-bit polyphony to raucous effect.
The RKW-2 sound engine imitates the behaviour of the audio loop in Follin's sound engine for the "Chronos" soundtrack. Each polyphonic voice writes a short square-wave pulse to the output at a regular interval based on its pitch/frequency; when two or more pulses collide, they are ordered into a pulse train and played immediately one after another.
Also available is RKW-1, a module that emulates the iconic sound of the ZX Spectrum's piezo beeper. It accurately recreates the timing behavior, multi-channel mixing modes, and sonic character of the Spectrum's 1-bit audio output system. Unlike chip-tune synthesizers with dedicated sound hardware, the Spectrum's beeper was controlled directly by the CPU.