Since 2016, our laboratory has researched three-dimensional sound-field synthesis using a 256-channel loudspeaker array with a high-speed 1 bit signal. We avoid digital-to-analog converters (DACs) by treating a high-speed 1 bit signal as an analog signal. The original system was based on FPGA, which requires advanced and complex hardware design and lack reproducibility. Therefore, in this study, we rebuild the system around a Raspberry Pi Pico2 W microcontroller, shifting functionality into software and improving reproducibility. Because few commercial devices can play back 1 bit audio, we release open-source design files to provide an environment where anyone can handle 1 bit audio. As an intermediate step toward a multichannel array, we developed a stereo playback device. 1 bit data stored on an SD card are output by the Raspberry Pi Pico2 W, amplified through CMOS buffers, and fed to loudspeakers. When the signal was played back at a sampling frequency of 3 MHz, the measured power spectral density was nearly identical to the original and there was no observable noise. Future work will support higher sampling rates, increase the channel count, and investigate wireless transmission of audio data from a PC to the Raspberry Pi Pico2 W.
Hayashida et al. (2025) studied this question.