The Lumiphone

Basic Sawtooth Oscillator BreadboardedI’m at the refining stages of a design for a light sensitive classic analog synthesizer that can be played with hand shadows. It may also be the world’s most inexpensive and easy to build analog synthesizer, as it does not contain any specialized components or special calibration circuitry. The result is a fun to play musical instrument with lots of timbral possibilities – pretty much identical to a Moog style synthesizer. The synthesizer, which I will call here a “Lumiphone,” bears its parameters to the player for instant connection, unobstructed by buttons and wheels or programming. It’s all raw at your fingertips, like a violin. This enables the player to make more expressive music, compared to that produced by your average keyboard synthesizer. It’s also a lot more work to play. You can’t just push a few buttons and hit play to get an acid baseline like the famous Roland TB-303. For this reason, even though structurally they are equivalent synthesizer designs, the lumiphone sounds different from the TB-303 and the like. I think the lumiphone will be most adored for its vast timbral pallet – which are all accessible at the flick of a wrist. It will of course also be adored for its accessibility in price and ease of construction.

Forgo tonality, gain simplicity and affordability

basic sawtooth osc schematicI found that the greatest barrier to entry in making a home brew synthesizer was the expensive and rare parts. It turns out that those special parts aren’t essential to the actual sound producing circuitry. I had to do a lot of research to figure out how to redesign the circuits without temperature and linearity compensation. The key was eliminating the voltage control paradigm and replacing it with light as the common control signal. In turn, the circuits reduce to a simple set of designs that any beginner hobbyist could put together in an afternoon. The trade off is of course that the pitch of the synthesizer may vary slightly given changes in temperature. This is irrelevant if you play the circuit by ear, rather than with a keyboard with fixed notes. It is also irrelevant to noise artists and experimental musicians who actively step away from tonality.

Light control

Resonant FilterLight turns out to be a convenient and interesting control signal. You can play the lumiphone with hand shadows. You can also play it with a microcontroller like an Arduino by varying the brightness of an LED. You can even play the lumiphone with the brightness of a computer screen – which can be controlled by a custom program written, for example, in Pure Data or even Javascript. CDS cells take the light cast on them to produce a resistance. This variable resistance is used in the synthesizer to control different things, namely the Frequency of the Oscillator, and Cutoff of the Filter.


Given the surprising versatility of this lumiphone, paired with it’s thrifty and accessible design I think this thing could be the beginning of something great. I hope it will be a useful design also for noise artists, circuit benders, and electronic musicians who will no doubt want to adapt it and borrow different elements to repurpose them for their own designs – like the Atari Punk Console. It also could be the beginning of a different kind of electronic music – a fresh start for the theremen. There’s still a lot of minor details to work out – like power supply design and deciding on the most accessible parts to call for – but soon I will be preparing some schematics and documentation for the project so that anyone with basic electronics skills can build one at home or in a classroom. In the mean time, if you click around on my blog enough you’ll be able to piece together most of what you need to build one.


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