2 MIDI CV/Gate Modules
A 4 voice Mono/Polyphonic and a LITE version
The purpose of this modules is to convert the digital MIDI signal into a voltage and a gate pulse. They can be used on vintage analog synthesizers which do not have a MIDI connection.
Analog synthesizers use voltages to control their parameters. For
instance, the pitch of the VCO (Voltage Controlled Oscillator)
depends of the voltage present at it's input.
This modules work with almost all 1 Volt/Octave synthesizers like
Dotcom, Yusynth, MosLab and so on ...To be used on EMS or Moog, the
Gate signal must be inverted. This can be done by software or with a
single NPN transistor.
Mono/Polyphonic version
This module has 4 CV (Control Voltage) and 5 Gate/Trigger Output.
Triggers and Gates are generally used to trigger the Envelope
Generator. When a key on the keyboard is pressed, a short pulse of +
5 V is send on the Trigger output. On the Gate output, the voltage
is hold as long as the key is pressed.
This module has 3 modes : a monophonic mode, a polyphonic mode with 1 MIDI channel and a polyphonic mode with 4 MIDI channel.
POLYPHONIC MODE
1 channel
In this mode 1 to 4 notes can be played simultaneously. The first
one is sent to the CV1 output, the second one on the CV2 and so on.
Each CV output has it's own gate. Additionnaly, the Pitch Bend Wheel
Value is added on each channel.
CV1 : Control Voltage of the 1st note
CV2 : Control Voltage of the 2nd note
CV3 : Control Voltage of the 3rd note
CV4 : Control Voltage of the 4th note
The Trig/Gate output gives a trigger signal for each note played.
4 channel
Each output responds to it's own MIDI channel
MONOPHONIC MODE
In this mode, only the last note pressed is played. The CV1 and
CV2 ouput give the value of the note and the Pitch Wheel
value. The CV3 send the Velocity output and the CV4 the Modulation
output. The Trig/Gate, Gate1 and Gate2 send the Gate signal, the CV3
and CV4 a Trigger signal.
This module use 4 very accurate 12 bits DAC (Digital to Analog Converter). The error can never exceed 1/32nd half tone. The range is 128 notes which is more than the 88 notes of the largest keybords.
The firmware is tuned on the tempered scale, but it can be easily modified to use other scales (Pythagoras, Zarlino, Rast or ancient chinese). Micro tonal scale can also be used (max 202 notes/Octave). It is even possible to tune each note independently.
In the Monophonic Mode, the Velocity value is converted to an exponential value for a more realistic play.
The MIDI channel is selected automatically. The module locks on the MIDI channel of the first note played. To change the MIDI channel, reset the module and play on the new channel.
LITE Version
Those of you who do not need all these features can build
the Lite version.
This version is much more simple and doesn't need any tuning. It has
only 2 CV output :
- CV + Pitch Wheel
- Modulation.
It has also a Trigger and a Gate ouput
The range is limited to 50 notes.
It only needs a single + 5 V or +7/23 V power supply so it can
easily be integrated in an existing synthesizer.
(Page updated the 27th of Feb 2009 )