This module has now been discontinued
The new revision issue 2.2 tbDAC board.
The tbDAC-2 is a top specification single channel midi to analogue convertor especially designed for the TB3030 and the 3031. The module may also be mounted into many other synths so long as certain conditions are met. This project is a joint development between myself and Trevor Page of Introspectiv.
It can run directly off the TB's own power supply of +/-12V, and requires only a few wires to connect it to the TB3030 or 3031 PCB.
The tbDAC-2 is also designed to drive any 1V/octave synthesiser if it can be powered off +/-15V.
Let us first have a look at the different outputs available.
Gate: +12V on, 0V off
Pitch CV: 128 steps of 12 bit accurate pitch voltage at 0.8V/octave for +/-12V supplies, or 1V/octave for +/-15V supplies. Pitch bend is added to this signal and can be trimmed to give the maximum bend interval. It can be trimmed to zero if required.
Velocity: 0 to 8V proportional to midi note on velocity. The velocity CV is then used by the the 3031 to control slide and accent.
Modulation wheel: 0 to 8V proportional to mod wheel position. This may be used to control filter cut-off within the 3030/1.
Slide: This output goes high when two notes are held down together. This operates similar to the auto-glide feature on the Oakley midiDAC and Roland SH101. By simply overlapping the gates of two consecutive notes, the slide output goes high. This is designed to enable the 3031's slide circuitry automatically.
The outputs are available on a set of solder pads along the side of the PCB. The design also features a midi thru.
Power Requirements
The module is normally powered by the 3031's internal +/-12V power rails. Alternatively, it may be powered by a separate +/-15V power supply for use with any 1V/octave synthesiser. It uses a optional MOTM style 0.156" MTA or Molex power connector.
Please note that if you require the midi-CV convertor to drive the 3031 AND another 1V/octave synthesiser at the same time you must have a +/-15V supply available.
When being used with the tbDAC, the 3031 is set to run at 0.8V/octave. This is the only way you can accurately get the full 128 midi notes from your convertor running at +/-12V supplies. If you are controlling your 3030/1 over midi this will not affect you whatsoever, since this operation is invisible to you as an operator.
Other Features
There is a note stack within the firmware to allow the tbDAC to remember notes pressed. Thus if two or more notes are pressed at the same time, the oldest notes will be remembered so that if the more recent notes are removed the pitch will return to the still pressed older notes.
Note retriggering is an switchable option to allow fast keyboard runs to be easily achieved.
Two optional LEDs, shown on the photos as directly fitted to the board, show MIDI status. They do not have to be fitted for normal operation.
Project Downloads
tbDAC issue 2.2 User Guide and Schematic
The older tbDAC-2.0 board fitted into a rack mounted Moog Rogue with internal mains supply. The Rogue was re-configured to run from 0.8V/octave to allow the tbDAC to control the Rogue over the full 128 note range of the midi specification.
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