On-line MIDImplant configurator can be found here
MIDImplant is a special circuit needed when you want to control your older analog synthesiser with MIDI. You can use this little board if your synth works with V/oct or Hz/V control. It takes about 2 seconds (or 4 keystrokes) to switch between V/oc and Hz/V ratios. It's calibrated at 1V/oct, but any ratio is possible, from 0 to over 2V/oct. Hz/V are available in 5 flavours, covering from 1 up to 5 octaves. Basic soldering skills are needed as well as a bit of knowledge about your synth. The service manual of your instrument, or at least schematic is most helpful.
Both CV outputs are monophonic, that means each of them can control one oscillator. They use last/top note priority. It means that whatever new note was played, it's immediately converted into proper voltage, regardless of the keyboard state before hitting the new key (if there were other keys pressed or not). If some of pressed keys are then released, CV output changes to represent the highest remaining note currently played on the keyboard. If the last key is released, CV remains at the level as before the release. Although this description may not seem obvious, described mode of operation is probably the most intuitive way of controlling pitch for monophonic analog synths.
CAPABILITIES
- 61 notes range
- User selectable V/oct or Hz/V
- Pitch Bend available together with notes at the same CV
- Fast response - valid CV and Gate 0.3ms after last MIDI byte
- Voltage accuracy within +/-0.5 cent for 1V/oct scale and +/-2 cents in all other cases
- User settings via "MIDI-learn" button, or MIDI Sys-Ex
- User selectable Volt/octave ratio with resolution of about 0.12mV/oct, easily adjusted with use of MIDI keyboard and/or Sys-Ex, no trimming screwdriver needed. CV ofset also possible in range +/-9mV
- User selectable Hertz/Volt range, covering 1, 2, 3, 4 or 5 octaves (up to 0.16-5V range)
- Gate output with V-trigger type of gating signal. User selected on-state: power supply level or 0V
- Gate retrigger, for every new note, or every CV change, or no retrigger
- posibility to reverse CV: 0V for top note, 5V for lowest note
- Each output of MIDImplant can be easily configured by the user to generate voltage representation of MIDI signals like:
- MIDI notes with velocity. One input represents pitch, the other one velocity, while GATE1 controls
note duration.
- MIDI notes on 2 different channels. Each Gate output works together with paired CV output.
- MIDI pitchbend with full 14-bit resolution
- Any of 120 available MIDI Continuous Controller, e.g. volume, modulation, etc.
- Channel Aftertouch, and Polyphonic Aftertouch
- MIDI Program Change - voltage level represents Program number received via MIDI
- Both outputs can work independently, that means one can be notes, the other - velocity. Or both can
represent pitch of notes on different channels. Or one can be Pitchbender, and the other one - modulation.
Combinations are endless.
- Each output can work on user defined MIDI channel, but if MIDI OMNI ON mode is selected, both outputs
respond to MIDI signals on any channel
- Both CV outputs can generate voltages in range between 0V and 5V
- MIDI THRU output
- activity LED
- dimmensions: 15x25mm (0.6''x1'')
Each MIDImplant is individualy calibrated to match parameters listed above. The calibration process is performed using laboratory 6.5-digit multimeter with base accuracy of 0.0035%. As final check, voltages for all 61 notes in both channels and in both modes (1V/oct and Hz/V) are measured again. All those 244 measurements are supplied to end user together with MIDImplant module. Calibration is performed at 15V power supply and 100k load at CV. Below is example graph for randomly selected MIDImplant. Horizontal axis range is 5 octaves.
See the video how MIDImplant passes calibration
INSTALLATION:
In order to install this device you need to find some key points inside your to-be-MIDIfied instrument: power supply rail (between 6 and 15V), ground (0V), and control voltage (CV+GATE) inputs. Most important is Voltage Control pitch input of your synth oscillator, or a point in the circuit where you can add it (usually it takes just one resistor to have additional CV input). Another important voltage is GATE signal, that starts the envelope generator. GATE is active whenever a key is pressed on a keyboard, while CV input tells the instrument about the pitch to be played. MIDImplant module provides 2 pairs of such signals.
That means you can control 2 oscillators, or make just one oscillator MIDI controlled, together with other control like VCF cutoff frequency.
Here you can find examples of MIDImplant use in analog synthesizers. Those are detailed instructions made specific to those instruments and MIDImplant as MIDI2CV interface. So far only 2, but the list here will grow:
How to MIDIfy Korg 700s (minikorg) using MIDImplant
How to MIDIfy Korg MS10 using MIDImplant
How to MIDIfy Yamaha SY1 or SY2 using MIDImplant
USER SETTING
Thanks to user friendly MIDI-learn function, you only need to press the EDIT button once, and generate the MIDI event you want to associate with CV output. For example to setup as note+velocity, press the EDIT button once, and play the lowest note on your MIDI keyboard. The module is ready to work with your keyboard since then. 2nd channel and tuning are also configurable via the same MIDI-learn button, see the manual for details.
More settings is available via MIDI System-Exclusive messages. Use your browser to select desired parameters and create plain MIDI file, that can be played in any sequencer, or straight from the computer to MIDImplant in order to edit all user settings.
Go to
MIDImplant configurator to set up your unit.
Extra possibilities available only via Sys-Ex are:
- different scales on CV1 and CV2 for example 0.9V/oct at CV1 and 1.2V/oct at CV2,
or V/oct at CV1 and Hz/V at CV2
- extended V/oct range adjustable from 0 to 15 V/oct in steps of about 0.12mV/oct
- offset CV in range +/-9mV
- Gate outputs on-state normal (supply voltage when on), or reversed (0V when on)
- Gate retrigger, for all new notes, or every CV change, or none
- combine Pitch Bend (+/-2 semitones) with note CV on a single CV output
- ignore note-off velocity, if velocity is set at CV2
- reverse note voltage, so lowest note gives highest CV
User settings are of course stored in nonvolatile memory, so you don't have to mount any button for setup. Just use a piece of wire connected to GND to activate edit mode during installation, any you will never need to change it again after you close the synth case.
download user manual
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