Inspired by the use of duophony on the ARP 2600 and Odyssey, this is a MIDI to CV Eurorack module with twin outputs: low-note priority and high-note priority.
Re-utilising designs from the polyphonic Euro-MPE project, this aims to be a high-precison, flexible, and performance oriented duophonic MIDI to Eurorack CV module. It's MPE compatible, so there is independent expression on each of the two notes.
There are three MIDI inputs
- DIN MIDI in
- USB device in, for DAW
- USB Host in, for USB keyboards
There are two voice channels, each with:
- color LED for gate and to indicate note played (12 color scale)
- Gate and Trigger, see Gate/LED.
- Tuning input (from oscillator), see calibration
- Oscillator pitch CV, highly linear 18bit, low tempco DAC
- includes pitchbend (Glide) and any microtuning
- See Pitch DAC
- Second (identical) pitch CV output (for dual oscillator voices, or for filter cutoff)
- Four MPE-compatible expression outputs (14bit) per voice, see Performance DAC
- Strike (attack velocity)
- Lift (release velocity)
- Slide (forward-back, CC 74)
- Press (aftertouch)
Any per-channel calibration curves are still applied, so in monophonic mode two different oscillators which have been calibrated will play in unison.
There are also eight general CV outputs (14bit), re-using the same board design that produces the two channels of performance outputs. See Performance DAC. Perhaps (considering mainly the Roli Seaboard):
Top row
- Slider1 (CC107)
- Slider2 (CC109)
- Slider3 (CC111)
- XY Pad X (CC114)
Bottom row
- Modulation Wheel (CC01+CC33)
- Expression Controller (CC11+CC43)
- Breath (CC02+CC34)
- XY Pad Y (CC113)
Probably, only Duophonic MPE mode is needed. See MIDI
Last received note is output on channel one. Any new note overides the previous note. Channel two duplicates channel one. Monophonic is MPE-enabled, just outputting to a single voice.
Configurable for MIDI channel, or all channels.
Lowest received note is output on channel one; highest received on channel two. Duo MPE is MPE-enabled,allocating MPE channels to voices based on lowest and highest note priority.
Configurable for MIDI channel, or all channels.
Like unison MPE, but channel two osc CV is offset (for exampe, by a fifth)
Not clear that the two non-MPE modes are needed. Better if the module accepts either MPE or non-MPE.
Like the original polyphonic EuroMPE, there is a tuning input per channel, which displays the current note; an auto-tuning mode can use this to calculate a linearising calibration curve. Because this is setup not playing, it's okay to go to a menu for this.
?? Because the tuner is in the same module as the MIDI interface, it knows when the gates are low and can do auto-tuning for drift control after x minutes of inactivity ??
For the pitch DAC, a Max 6226 hermetic ceramic is used, see Vref MAX6226. As that prototype had problems, and alternative is the Vref LT1236.
For the performance DACs, the internal reference on the octal DAC is easily sufficient.
See MPU board.
See Power
Not settled, but this is the current panel concept (SVG)
and also current panel with boards and components (SVG)
