fotosis / we like to make stuff: For Sale: Optically Controlled Synth / Theremin

John has just completed this antique cased optical theremin and it is currently up for auction on Ebay.

Here are the details:

“This is an optically controlled noise maker (Sound Synthesizer). It comprises of three LDR's that control the sounds produced and the microprocessor controlled effects.

There are three control knobs. The first is for LDR switching speed where the sound synthesis chip alternates between two LDR's, measuring their values producing two different tones depending on the level of light falling on each. This effect creates strange sixties sci-fi sounds. The second knob controls the sine wave intensity which is handy when you apply effects like distortion and fuzz to the signal before amplification. The third knob controls the output volume.

There are several toggle switches on the unit. On the left hand side, the first sets the device either for high or low pitch sounds ranging from low rumbling drones to high pitch chirps andwhines. There is a power switch in the centre to turn the synth on and off, and a switch to select the LDR switching effect. The knobs on the right engage the microprocessor which measures values on the first LDR and does one of two things. The first thing it does is only allow the device to produce sound when a certain level of light has been reached which is useful when you don't want the unit to play itself (Be silent until you interact with it). The second microprocessor controlled effect toggle again sets a threshold which keeps the device silent until a certain level of light has been reached but this time it pulses the sound on and off increasing the speed of the pulses when the level of light on the LDR increases sort of like a built in tremolo effect.

There are three LED's. The centre LED indicates power on and the other two the state of the two microprocessor controlled effects.

The unit is housed in an antique (19th century) handmade French jewelery box stamped with the mark of Pierre Dujardin Paris. I restored the box to make it as robust as possible and left the weird repairs and different layers of paint that had been applied by the many previous owners that give this device an authentic aged and vintage look, sort of like an old piece of lab equipment or a prop from a mad scientists lab.

Various other visual garnishes have been added such as the leather straps that hold the lid open and the foam that lines the inside of the lid.

(the inside is coated in a latex based plastic like preservative and pine sections have been added to the interior corners using epoxy)

This synth/noisemaker-theremin thingy runs off a 9V power supply, I'm including a brand new Boss PSA-230P (Still in box) with the unit.

The output is loud as its at about line level when the sine wave intensity is at max and the volume fully on.

Here is a youtube video of the device in operation with just a bit of reverb added by a Boss DD3.

The unit can be played with your hands or with light sources. A bike light produce the best effects, creating techno-like beats by selecting the flashing settings on the light and by placing them directly over the LDR's. I've recently discovered that by running the unit into an Electro Harmonix Guitar micro-synth, a whole range of other sonic possibilities were presented.

If you require other sound samples I will be more than happy to supply them just email me at johncavanagh(at)gmail.com just replace the (at) with @

NOTE: I will actually ship to Europe and the US if you contact me first so I can figure out postage, just email me and we can discuss postage etc...”