Grove Audio News : Project "BusyBox"

Monday, May 28, 2012

Project "BusyBox"

This 6MU module contains a complete synthesizer voice and an internal MIDI to CV converter. Internal routing is roughly based on the Moog Minimoog Model D. An analog routing system controlled by a processor offers alternative routing schemes to extend the usefulness of the unit as a standalone synthesizer. A couple of extra features not found on the Minimoog have been added such as ring modulator, linear FM modulation of the VCOs, and voltage controlled amplifiers on each VCO and external audio sources. The MIDI to CV converter can produce up to four CV/gate pairs and internal control voltages based on channel control messages from an external sequencer or keyboard controller can extend or replace internal modulation sources for the VCOs, the audio mixer or the filter. The filter core is a 4 pole low pass filter which feeds a signal matrix and analog switch that allows one of sixteen possible filter modes to be selected. Two envelope generators can be used to modulate parameters of the filter and apply a contour to the main audio output VCA. The depth of modulation can be controlled by the modulation wheel of a connected MIDI keyboard controller.

The front panel of the prototype modules. The prototype is constructed of existing module boards. The final production version will contain all circuitry on three printed circuit boards which will be mounted in parallel with the front panel for an extremely thin module depth. This will permit mounting the unit in a standalone desktop enclosure with built-in power supply.

This view shows the unit from the left rear. The envelope generator boards are on the left. On the right is one of two VCO boards containing the full-function 1V/Octave VCOs.

This view, from the right rear shows the MIDI to CV converter on the right. The center panel will receive the filter board, mixer board and the routing matrix board.

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