Wednesday, 31 October 2012

Rainsbury.Net: Micro Modular

I have spent the past few months resurrecting a project I first started back in 1973(ish), my Micro modular synthesizer. I plan to release the plans as an e-Book next year, but wanted to get some feedback about what people would expect to see from the project.

Design spec

  • Every module must cost less than £10, including all components, connectors and the front panel, but not the knobs.
  • Every module will be the same size, around 6"x3", more about that later.
  • No specialist parts, indeed many can be recycled from old projects.
  • All connections will be via 4mm banana plugs
  • A 10 Unit rack will cost less than £20 including power supply.
  • No direct connection to the mains
  • All external connections through 1/4" jacks.


  • The VCOs will not be stable, or linear enough to play tunes, this is an effects and treatment device only. However this doesn't mean it isn't musical a later extension will allow you to use a cheap home keyboard as a sound source.
  • Power supply will be external, +/- 9Volts
  • All modules will be built on veroboard, there will not be a pre-made PCB. But then that's how the Synthi-100 was made.
  • There will be printable front panels which you will have to cut out and stick yourself, so it will be as good looking as you want to make it.
  • You will need to be able to solder, cut 3mm plastic sheet or thin plywood accurately and have a bit of patience.

Basic design

The basic design will be for a frame that can take up to 10 of the modules listed below. Plans for this, the power supply and output module will be listed here before the book is published.
I am planning to publish designs for all of the modules listed below, but so I don't delay publication they won't all make the first edition, however once you have purchased a copy the updates will be free.

Complete or partially complete

  • Power supply module (mandatory)
  • Output module (mandatory)
  • VCO, exponential, almost 1V/Oct but unstable, 1 V/C input with attenuator,  one without, ramp only out. (Might include sync if I can do it for under £10)
  • LFO, manual frequency, square, ramp or saw output. 3 ranges.
  • Joystick, provides +/- 9V on each axis. Might include trigger button if I can fit it on the panel under budget, this one is going to be hard to do.
  • Ramp to square + PWM module
  • Voltage controlled filter (Moog ladder) approx 1V/Oct
  • Voltage Controlled Amplifier. No idea yet
  • AR generator, with repeat so can be used as second LFO.

Planned but work not started 

  • 7 stage sub octave module
  • Noise generator
  • Input amplifier
  • Envelope follower
  • Ring modulator
  • Sample and hold
  • 8 stage trigger sequencer
  • Tap pad and trigger
  • Speaker/headphone amp
  • MIDI interface for control voltages. This one is quite complex, and will probably need a PCB to be made so it can't be done for under £10.
Yo can include any number of modules, in any configuration so long as the rack is large enough and the power supply can provide enough current.
I will publish photographs and the initial designs here early 2013.

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