Neon Bulb Synthesiser
It's an audio synthesiser made entirely out of neon bulbs.
produced by: Ewa Justka
It is an audio synthesiser, which is using pre-transistor, optoelectronic technology from early twentieth century – glowing neon lamps- as logic gates, which are the fundamental binary operators in computing. It is a fourteen steps sequencer (ring counter) with fourteen oscillators (each step triggers a sawtooth oscillator, of which pitch can be modulated) built entirely using bulbs. The more steps, the more random the sequence becomes, this applies also to the voltage (it runs on 180VDC).
The operation behind the neon bulbs logic lies in the gas that is being charged and discharged, depending on the current. Due to hysteresis (which is basically dependence of the systems output on the past input) neon bulbs can be used as on/off switch, which is what binary logic is (1 vs. 0). That gives a possibility of creating not only oscillators, but also more complex sequential logic.
There are three outputs of the synth: firstly, the sound, then the mini CRT oscilloscope, where the audio signal is displayed, and the nixie numerical tubes, of which cathodes (negative plates) are triggered with each sequential pulse.
The design was based on schematics found in Glow Lamp Manual written in the 60s. I experimented with components and values a little bit.