This module has now been discontinued but replacement PICs are still available from us.
The midiDAC is a top specification single channel midi to analogue convertor. This project is a joint development between myself and Trevor Page.
The recommended panel layout for the new issue midiDAC-3 module
The midiDAC is designed to drive any 1V/octave synthesiser. However, it has been designed to fit beautifully into a MOTM or Oakley modular system. Let us first have a look at the different outputs available.
Gate: +5V or +15V gate.
Pitch CV: 128 steps of 12 bit accurate pitch voltage conforming to 1V/octave (trimmable). 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.
Pitch Bend: This signal is available individually. It is bipolar; so with no bend, the output CV is zero.
Velocity: 0 to 10V proportional to midi note on velocity.
Aftertouch: 0 to 10V proportional to midi channel aftertouch.
Legato: This signal goes to +5V when two notes are played at the same time. This can allow slides to be switched in at will; TB303 style.
Modulation wheel: 0 to 10V proportional to mod wheel position.
CC: Continuous controlled number 100.
The outputs are available on two sets of 4-way 0.1" connectors at the base of the board. The design also features a midi thru.
Power Requirements
The module requires a split supply of +/-15V and uses a standard MOTM style power connector. Please note that +/-12V is not supported on the new issue midiDAC.
Other Features
The midiDAC also includes a TB303 style slide circuit. This can be turned on and off manually, or by playing two notes at once. The pitch will glide up or down to the most recently pressed note. A pot can control the speed of the slide, or simply leave it fixed at one value by choosing a suitable resistor. This circuitry can be easily linked out if it is not required.
There is a note stack within the firmware to allow the midiDAC 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.
New note retriggering can be switched in or out to suit your playing style. Note retriggering will allow you to play super fast keyboard runs. Each new note pressed will retrigger the synthesiser's envelopes irrespective of how many others are still held down.
Andy Wilson's issue 2 midiDAC in the MOTM compatible front panel. The new issue 3 boards are similar in size and complexity, but use Spectrol 248 pots.
The Printed Circuit Board
The issue 3 PCB has been designed to fit within a 2U across MOTM style modular face plate. It has three PCB mounted pots to facilitate TUNE, BEND DEPTH and SLIDE RATE. The pots are spaced at 1.625". Midi channel is selected by four lines in traditional binary fashion. Thus midi channel can be switched by either onboard DIP switches or links. This could also be done by a 16 position rotary HEX switch mounted on the front panel, but this is not provided on the standard midiDAC front panel design.
The pots I use on this module are the Spectrol 248 series. They use specially made pot mounting brackets to ensure a firm connection to the front panel and PCB. They are strong enough to hold the PCB in place without any further support.
The PCB is double sided, has through plated holes, solder mask both sides and has full component legending. Board size is 111mm deep x 133mm high. Power is admitted to the board via 0.156" Molex connector.
Project Downloads
Issue 3 User Guide and Schematic
Front Panel database
A Schaeffer front panel can be made for a 2U wide midiDAC module . The database can be found here mididac3.fpd. To read this file you will need a copy of 'Frontplatten designer' from Schaeffer. The program also features on-line ordering, so its now even easier to buy your panels from Scheaffer.
The company are based in Berlin in Germany and will send out panels to anywhere in the world. Delivery to the UK normally takes around ten days. For North American users you can also order your Schaeffer panels from Front Panel Express.
MOTM style Front Panels
See Dave Bradley's great service using real MOTM blanks to create perfect MOTM compatible panels for some of the Oakley Modules : www.hotrodmotm.com
Parts lists for US builders
Builders based in North America can now find full parts lists, complete with order codes, for many of the Oakley modules. Larry Hendry has kindly provided the web space for customers to upload parts lists. Go to www.wiseguysynth.com for full details.
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