MESS Modular Electronic Sound System, for peanuts
background | pizzatronics | download plans
*audio/video to be added*
Analog modular synthesis systems allow the musician to make their own bespoke synthesiser by wiring together a number of more basic units or modules, analogous to how Max/MSP patches are wired together digitally. They have a long history and continue to be popular, although expensive. I had the opportunity to teach a class on building analog electronic music circuits. By having each student build and keep at least one module, groups of students can then construct modular systems by connecting their modules. This also has the advantage that concepts of electronics and systems can be introduced before going into the detail of the module circuits.
The first module I designed, MESS-1, is a voltage controlled oscillator (VCO) with some twists to give it more flexibility:
It actually consists of 4 independent sub-modules that can be linked with external wires, an oscillator, a pulse gen, and two amplifiers with scale and shift presets to create different control or audio waveforms. Default links configure the module as an 'Atari Punk Console' with voltage control, capable of pulse width modulation (PWM), frequency stepping and other effects.
The ICs used are inexpensive 556 and LM358, which run off a single 9V supply. The 556 is far from ideal as a VCO but its cost, easy of use, and general quirkiness make up for this. The amplifiers are important for getting the most out of the 556 voltage inputs. PCBs were produced to make it as easy as possible for students to make progress initially. Connections are made using a mains header block, which allow several wires to be attached securely at each point, again very cheaply. The presets are not designed for performance control - additional potentiometers can be wired in externally. To make a low frequency oscillator (LFO) just connect an extra capacitor in the block. The downloads provide construction and useage details.
The second module designed, MESS-2, is a step sequencer, including a few bells and whistles such as cycle length control, direction control, binary count output, freeze, keyboard.
Students that build this are encouraged to make the core part on breadboard first, which is relatively quick to do. Stripboard plans are also provided. I am using cheap press-to-make switches and header clips for permanent throw switches.
MESS-3 is a simple analog gate which can also effectively be used as a voltage controlled amplifer (VCA) for pulse wave signals. A simple attack and decay envelope generator is included for the voltage control input. Only rough schematic plans are given, the idea is that the student fills in the details themselves.
Possibly in the future I will add plans for a voltage controlled filter (VCF) and more generators.
And here is what it looks like when you connect up several modules, using a pizza box to maintain the low cost ethos:
Schematics and printed circuit board (PCB) designs can be downloaded here:
Eagle PCB deisgn files and generated Gerber files are included, as well as guides showing default sub-module connections and suggested module configurations.
Note: Because these circuits are driven from a single power supply, the audio outputs have DC offset and should be decoupled when connecting to an external amp or headphones. A simple example is included.