Andrei Holingher has built a Nixie tube spectrum analyzer with an S/PDIF input. Inspired by Will Yager’s Rust-based Nixie Tube Audio Meter, the project ports that functionality to Arduino-compatible code, incorporating necessary hardware changes along the way.

Four SAMD21-based QT Py clones drive four tubes each, while a VN7140 Power Management IC distributes power. LM1117 voltage regulators power the 5V and 3V3 microcontrollers, with NCH8200HVs boosting power to the Nixies. The digital optical audio signal is processed by the Teensy Audio Library, then band-filtered into bins, represented by the tubes, with a potentiometer on each for further calibration. Schematics, BOM, firmware, and more can be found on GitHub, and a mesmerizing demonstration can be seen below.