I've decided to post a schematic for an optical theremin / synth that is a simplified version of our first creation, Fotosis No. 001. Its based around the XR2206 function generator which produces the sound (Sine Wave) and the 40106 chip that I use to trigger the LDR switching function on the XR2206. The controls are simple, three pots and three toggle switches. The pots control volume, sine wave intensity and LDR switching speed and the toggles turn LDR switching on / off (S1), (S2) for high and low pitch setting and (S3) which gives you the capability of redirecting the timing resistor pins on the XR2206 chip to some other form of resistance.
You could build a hybrid sequencer / optical theremin using a micro-controller like the Arduino board with a few opto-couplers switching the timing pins through resistors (4N37's work well) or make a noise maker using the spare Hex Schmitt Triggers on the 40106. There are many possibilities. All of the Capacitors are 1uf ceramic (Farnell part number 110-0420) except C4 which is 0.33uf polyester (Farnell part number 116-6040) all resistors are 1/4 Watt. The LDRs are 1M Ohm in total darkness and the whole circuit runs on 9V dc.
Just posted "Fotosis 002" for sale onebay.co.uk, you can view the listing here.(This item is now available for purchase at our Etsy Shop) Starting bid is £175 sterling. I so wish I could sell these for less so more people could be in possession of very their own noise machine (because everybody needs a noise machine) but alas components are not free and it took me like four days to build it from scratch so I felt the starting price was as little as I could charge. Anyway still messing around with it trying to get as much playing (Testing) time with it as I can before I have to give it away and I still think its amazing. The picture on above is the development process of Fotosis 002 where I carefully connected various other home made circuits to the half finished device so I could assess nice values for the components that influence the sound before soldering them into place. I like to use different value components in every device even if the devices look the same on the outside in order to give every instrument a unique voice.
Here is a new sound clip I recorded yesterday. Its the voice of Winston Churchill doing the we will fight them on the beaches speech being played from my laptops headphone jack via the ring modulator with oscillator two (The square wave one) being used as the carrier frequency.
We have been very busy the last two weeks deciding on a final design for this instrument which will be our main product from this point forth. The challenge was to create something that was not so complicated it would be really difficult to build or play and not so simple that the person playing it would get bored after an hour or so thinking that they had discovered all the instruments potential. In the end we built "Fotosis No. 002" which is comprised of three sections, optical theremin (Sine wave), noise maker (Square wave) and a passive ring modulator.
The first section is an updated version of our premier instrument "Fotosis No. 001", which was an optically controlled sine wave generator. This section no longer has built in microprocessor controlled effects, I did this to reduce complexity but I have added the ability to bring the sound synthesis chip under the control of two pots instead of the LDR's with the flick of a toggle and I've also added a kill switch and momentary kill bypass button to the output (Thanks Ian for the pointers). This section can be used on its own as an optical theremin or as a drone machine, there are one or two other functions but they would take a while to explain so ill leave them a mystery for now:-)
The second section is a simple enough square wave noise maker that produces nice high and low pitched tones, squeals and fuzz sounds. On its own it can generate quite a few interesting sounds, some scary, some annoying. This section will keep you occupied for a while as a noise maker but its real purpose is to provide the ring modulator with a carrier. Like the first optical section there is a volume pot a kill switch and kill bypass before the output.
In the top of the unit there are five standard audio jacks the one on the far left belongs to the optical section, the jack on the far right is dedicated to the square wave noise maker and the three in the middle concern the ring modulator.
These three jacks (In the middle) from left to right are ring mod. input, carrier input and ring mod output but actually they are interchangeable. Either oscillator optical or noise maker can be used as the carrier that will modulate whatever signal is on the input which can even be from another instrument such as a keyboard, guitar, laptop head phone output, AM radio etc. anything that is at line level can be fed into the ring mod and distorted and made all weird. Passive instruments need to be amplified by some kind of line driver as would be the case for a guitar or bass where an overdrive pedal would be needed to drive the input transformer.
The ring mod. is a passive system as in it uses no power and contains no active components. It is made from two 1:1 ratio CT transformers and four matched germanium diodes. The sound produced is often bell like, sometimes lightly distorted and generally way out weird. You can also bypass the ring mod. section with the flick of a toggle switch so your input signal is untreated. You can have hours of fun modulating oscillator one with oscillator two or vice versa and looking for interesting tracks in your music library to play through it.
The whole unit is housed in a wooden box with a pine frame on the interior, everything is first glued together and then fixed to the pine frame with many many stainless steel screws. The box is coated in a Tolex like material that I found in my local art store to make it look nice. There are also steel corners to protect it from knocks and rubber feet on the bottom so it wont scratch the hell out of you table.
The whole thing runs off a standard nine volt negative tip positive shell PSU, I generally supply a Boss PSA 230 wall wart with each unit sold because I find they are pretty robust and reasonably priced.
It took me about a four day to build this not working full time of course and I've been testing it continuously since I finished and I have yet to find all possible permutations of knob settings.
Ill be putting it up on Ebay pretty soon so if anyone is interested in buying it just let me know before I auction it.
Here are some sound samples. To download, the download button is at the bottom of the page that the download button brings you to if that makes any sense? You'll see:-/
If you have any more questions regarding this device feel free to contact me ill be more than happy to send you extra sound clips of the unit in action or answer any questions you have relating to it.
Back in March, we decided to build our first simple theremin. The process took an on/off time period of a few months, not rushed because it was a hobby project.
The excerpts below are from previous blog posts I have made about the process, the fun of making it and the final outcome.
"As some of you already know, I like to create things from recycled materials with John. We laboured over an awkward website to get our parts last week and John finally had the time to assemble a test this evening. The sample we used for this make is from the 'Minimum Theremin' by Harrison Instruments.
First off is the construction and testing on the breadboard. After all is working right, the time is for the physical testing. We used several metal objects including a lid, coat hanger and bread knife. The approximate cost of this project is 15 Euros. So How Does It Sound? See for yourself and download the video here and let me know what you think.
It all seems to function and now we have to decide on a design for the casing and look. We look around and choose an empty metal case from a Smallstone Phaser with very cool Russian trademark and an old rusty saw I’ve had dying on my balcony for 5 years."
The first part of finding a suitable schematic, parts and materials was invaluable. The second proved to be even more rewarding because of the hands on nature of the work.
"We selected a rusty saw as the aerial and recycled the casing from an old Russian Smallstone phaser box. This is the work involved to finish it (though for anyone who makes things will know, you’re never really finished)."
"We started off getting rid of the rust and the hardened paint on both objects by soaking, scrubbing (and suffering major inhalation problems) with a load of white spirits. The ‘guts’ of the theremin was completed in about 3 hours prior so this proved to be the hardest part.
24 hours later we started sanding. We took out J.’s Dremel and worked on softening the saw’s edges for safety. We continued sanding the phaser case.
By early evening, we managed to clean the two objects and with an extra 13-14 Euro purchased an anti-rust varnish. We coated and waited…
By night, we polished the saw and selected the knob controls and other remaining aesthetic needs. The theremin was finally put together as J. used some foam to attach the prototyping board, guts and all!"
The theremin wasn't the most sophisticated but we lost no opportunity to enjoy the conception of it or discover the many nuances and improvements we could alter with common distortion. Mostly, we just had a great time playing with it and showing it to friends.
I am planning to complete a matching optical theremin sometime soon.
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...”
We are still setting up this site so make sure to check back for updates. Our soon-to-be developed blog will include our sales information, other traditional and electronic instruments, recycled art projects and various other DIY happenings.
Feel free to contact us by email, info is on your left.
We create handmade analog electronic andelectro-acoustic instruments. Each unique build is designed and built by us. Our blog includes the building process, in combination with our other DIY projects, music and interests.
I've decided to post a schematic for an optical theremin / synth that is a simplified version of our first creation, Fotosis No. 001. Its based around the XR2206 function generator which produces the sound (Sine Wave) and the 40106 chip that I use to trigger the LDR switching function on the XR2206. The controls are simple, three pots and three toggle switches. The pots control volume, sine wave intensity and LDR switching speed and the toggles turn LDR switching on / off (S1), (S2) for high and low pitch setting and (S3) which gives you the capability of redirecting the timing resistor pins on the XR2206 chip to some other form of resistance.
