Constructional Difficulty: Moderate - Large number of parts with some simple setting up required
The midiDAC is a top specification single channel midi to analogue convertor. This project is a joint development between Oakley Sound and Trevor Page.
The recommended 5U high panel layout in Schaeffer's natural finish aluminium
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.
A completed issue 3 midiDAC in a natural finish Scheaffer panel
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.
Prices
MidiDAC ready made module......................................... 200GBP NOW SHIPPING
midiDAC issue 3 PCB and preprogrammed PIC ......... 30GBP
midiDAC pot bracket kit
..................................................... 3GBP
midiDAC pot kit
...................................................................
9GBP
MAX551ACPA 12-bit DAC................................................
9GBP
midiDAC pre-preprogrammed PIC only ......................... 10GBP
The midiDAC pot kit contains three Spectrol 248 or BI TT pots sufficient to make up one 2U wide panel. No knobs or switches are provided. The midiDAC pot bracket kit contains three Oakley pot brackets and three extra pot nuts. The brackets are especially made for us to hold the PCB mounted pots safely to the PCBs and cannot be purchased anywhere else.
All other parts can be purchased from you usual electronic component supplier.
See the prices page for ordering information, shipping charges and payment methods.
All prices include VAT at UK rates. Shipping/postage is additional to these prices. See also the FAQ page.
Project Downloads
Issue 3 User Guide
Front Panel database
A Schaeffer front panel can be made for the 5U high 2U module in either standard black or natural finish. The databases are available here: Black or Natural Silver
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.
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