Elby Designs Chaotica

ed120_front_2Ian Fritz is known as developer of electronic circuits which utilise the Chaos Theory. One of these circuits that is called Chaotica, can be purchased from Elby Designs as assembled Eurorack module Panther ED120 or as DIY kit. The Chaotica is a third-order chaotic system with extensive voltage control.

The Elby Designs, an Australian company named after thirst letters of its owner, engineer and musician Laurie Biddulph, supplies kits and accessories for the synthesizer do-it-yourself (SDIY) market. The company is mainly known for ASM Synthesizer and also known as supplier of the modules developed by another engineers such as Ian Fritz and Ken Stone. I will write about Ken Stone and his Cat Girl Synth project later. Now I would like to return back to Chaotica.

How it works

It’s hard to understand the way it works without oscilloscope, but mainly, Chaotica imitates the process that can be imagined as some kind of particle moving in a 3-dimensional space. Three variables, x, y and z keep the coordinates of this particle. oscilloscopeThere is also vectorized time variable that can be reset and can flow at various speed. After reset, this “particle” always appears at the same point and starts to move in complex elliptic trajectories. The full path is completely determined by system parameters and can by repeated, but if some of the parameters changes even slightly, the path can change almost unpredictable. This is the typical behavior of the chaotic system.

The parameters of the module are CV-controlled and manually controlled. The manually controlled:

  • NL (Non-Linear) Drive knob: controls the level of non-linearity of the function. Practically it is the control of unpredictability.
  • Tame-Wild switch. Toggles character and complexity of the generated path.
  • Eyes switch (1/2): Toggles the number of the Eyes (see the illustration).

ed120_singles ed120_doubles
The voltage controlled parameters can be set manually with knobs or set by applied external voltage attenuated by the same knobs. Here they are:

  • Rate: Exponential control for speed of the operation. The range is from LFO-alike rate to kHz rate.
  • Damping: As named, the damping of the curves.
  • Offset: Common offset.
  • Gain: The level of the signal. In fact, this is built-in VCA.
  • Reset-Inhibit input: A trigger sent to this input will reset the time parameter.


I recommend to watch this video because it explains the function of the module very well. Also it is the actual operation manual for the Chaotica!

Price and delivery

Well, the price is fair enough for rare and complex module, but delivery of two modules was really expensive (60$) and even tracking number was not provided. In some circumstances it will be cheaper to buy second-hand assembled module in Europe/North America then buy kit from Australia. Of course, delivery rate may vary, but for Russia it was high.



The kit consists of 8 PCBs: 1 main, 3 interface boards and 4 tiny adapter boards for single jacks/switches. ed120_PCBThe boards are well-made: two-sided, metalized, solder masked and silk-screened. The boards are connected by several bus wires and tiny adapter boards are soldered to the main board with a long IDC pins. The multi-coloured jacks looks very nice.

ed120_jacksElby Designs are good with packaging: every value is packed into separate packet marked with sticker. The faceplate in my kit was funny: two 1mm plates are glued together to form 2mm plate. I think it was some misunderstanding between Laurie and one of his suppliers. There was no some common scratch-protection on the faceplate but it went through delivery in a perfect condition.

The potentiometers used in the kit is made by Alpha. It is honored manufacturer, making long-living pots. But there was few pots with tabs already stripped off. That’s strange but pots seemed to be new. It is not a real flaw. I want to tell about the real ones.

The main flaw is lack of detailed assembly documentation. The links are given in a uncomfortable way (try to click on the product information link at the product page, you will understand what I mean) and the mark-up messes up in FIrefox. Existing documentation is limited to very brief assembly instructions, Bill Of Material and the silkscreen drawing. All of the components on the overlay are presented as designators instead of values. It makes the assembly process very slow because you always need to find the designator in the BOM and then unpack corresponding component. By the way, it has one 100K resistor missing (R225).

Nevertheless, the assembly process took just 4 hours of time that is not so long for this level of complexity. Due to initial design, the board didn’t need to be adjusted and is ready to work once being assembled.

An impression on use

The module is very interesting thing that can be used for a variety of tasks. At high rate it may be used as some noise/drone oscillator. At slow rate it may be used with a system of VCAs/panners to control two or three-dimensional positioning of the sound or it can be used in the same way with any other system of parameters. It also can act as non-linear, non-static quadrature generator due to frequency-locked signals at the outputs. It is pleasant to watch Chaotica’s output at the scope, so it also may be used in analogue video-systems as shape generator.

The one more little flaw of the Chaotica is its depth: 94mm that makes it unable to be installed into cheap Doepfer mini-case.


The Chaotica module is connected to the Oscilloscope in XY mode. The X output goes right to X channel, and both Y and Z outputs go to VC-panner modulated by triangle LFO. The result goes into scope’s Y channel. This gives some pseudo-3D effect that gives better understanding of waveforms generated by Chaotica.


ed120_moduleThe Chaotica is original module full of complex math. Elby Designs made a strong product with beautiful and informative faceplate and high-quality components but doesn’t complete the assembly documentation. After all, there is no serious flaws and for it’s incredibly functionality, the Chaotica is high-rated and highly recommended, especially as the fully-assembled module.

The Modularsynth rating: 9/10

3 thoughts on “Elby Designs Chaotica

  1. Pingback: AVR Synth 16 | Модульные синтезаторы

  2. Aleksandr Plotnikov

    У меня в наборе не было 2х конденсаторов, правда положили лишний шлейф )) Лицевая панель склеена (!) из 2х миллиметровых. И главное, что взбесило, диаметр отверстия под светодиод больше диода примерно на 1.5 мм.

    1. rpocc Post author

      Лишний шлейф ко мне тоже клали, кстати. Про склеенные панели я писал, а вот история с дыркой меня удивляет. Пихни туда 5-миллиметровый, будет винтажнее смотреться.

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