Fotosis No. 002 Optically Controlled Synth / Ring Mod. / Noise Maker...

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 Youtube clips...



Part 1...
Part 2...

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:-/





Download audio directly.
Clip 1...
Clip 2...

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.