Page 1
Mutable Instruments | CVpal - User manual
https://mutable-instruments.net/archive/cvpal/manual/
Mutable Instruments’ CVpal is a DIY USB MIDI to CV interface - enabling you to control an analog synthesizer or
modular system from a computer or smartphone/tablet equipped with a USB port. The CVpal is class-compliant
and as such, does not require any driver. It features various conversion/voice allocation modes, covering
monophonic, duophonic and drums/triggers applications.
Before moving forward, it is important to state some limitations of the CVpal - most of them due to its ridiculously
simple design:
The CVpal is a USB device not a USB host! It can be connected to ‘active’ devices such as smartphones, tablets,
laptop or desktop computers, but not to USB MIDI controllers.
The CV output is in the 0 .. 4V range - so a tessitura of 4 octaves is covered. The CVpal does not support V/Hz
conversion; only V/Oct.
The Gate output uses V-trig, has a 5V high level, and a direct polarity (note on = 5V, note off = 0V). Most Eurorack
modules use a trigger level below 2.5V and can thus be triggered by the CVpal. If a module or synth requires a
higher level, a level conversion circuit such as the CD4504 can be used. Polarity inversion can be implement with a
CD4049 or with a software hack. S-trig conversion can be implement with a few parts.
The CVpal works optimally with iOS, OS X >= 10.6.3 or Linux kernel >= 2.6. On other operating systems, the
messages might be delayed by up to 8ms, causing a very jittery timing!
The CVpal can either be mounted in a Eurorack system, or used as a standalone box. In both cases, it does not
need any external power source as it is powered by the USB bus.
1 sur 5 19/01/2018 à 15:52
Page 2
Mutable Instruments | CVpal - User manual
https://mutable-instruments.net/archive/cvpal/manual/
The CVpal interprets MIDI messages differently depending on the MIDI channel on which they are received. For
example, when receiving messages on MIDI channel 1, it behaves like a monophonic synthesizer and outputs a
CV/Gate pair. When receiving messages on MIDI channel 10, it behaves instead like a drum trigger converter
and outputs a trigger for 4 drum instruments.
This mode is enabled when any MIDI message is received on channel 1. The CVpal behaves like a classic
monophonic CV-Gate converter implementing most recent note priority.
OUT 1: Note CV
OUT 2: Velocity CV
GATE 1: Gate
GATE 2: Gate
This mode is enabled when any MIDI message is received on channel 2. The CVpal behaves like a monophonic
CV-Gate converter implementing most recent note priority, but the primary Gate output is now a digital square
oscillator!
OUT 1: Note CV
OUT 2: Velocity CV
GATE 1: Square oscillator playing the received MIDI note
GATE 2: Gate
Bonus digital square oscillator! Hell Yeah!
This mode is enabled when a MIDI message is received on channel 3 or on channel 4. The CVpal behaves like
two independent monophonic CV-Gate converters with most recent note priority. One of them listens to notes
received on channel 3, the other on channel 4.
OUT 1: Note CV for channel 3
OUT 2: Note CV for channel 4
GATE 1: Gate for channel 3
GATE 2: Gate for channel 4
2 sur 5 19/01/2018 à 15:52
Page 3
Mutable Instruments | CVpal - User manual
https://mutable-instruments.net/archive/cvpal/manual/
This mode is enabled when a MIDI message is received on channel 5. The CVpal behaves like a duophonic CVGate converter with voice stealing.
OUT 1: Note CV output 1
OUT 2: Note CV output 2
GATE 1: Gate
GATE 2: Gate
This mode is enabled when a MIDI message is received on channel 6. The CVpal converts continuous
controllers (CC) 01 (modulation wheel) and 02 (breath controller) to control voltages.
OUT 1: Modulation wheel CC (01)
OUT 2: Breath controller CC (02)
GATE 1: Binarized value of CC 3
GATE 2: Binarized value of CC 4
These modes are enabled when a MIDI message is received on channel 7 or 8. The CVpal behaves like a
monophonic CV-Gate converter, with an additional CC value produced on the secondary output.
OUT 1: Note CV
OUT 2: Modulation wheel or breath controller CC (01 or 02)
GATE 1: Gate
GATE 2: Gate
This mode is enabled when a MIDI message is received on channel 10. CV Outputs 1 and 2 are respectively
triggered by the MIDI notes 36 (kick drum on the GM drum map) and 38 (snare drum on the GM drum map).
Gate outputs 1 and 2 are triggered by the MIDI note 40 (snare drum 2) and 46 (closed high-hat).
OUT 1: BD (note 36) trigger
OUT 2: SD (note 38) trigger
GATE 1: SD2 (note 40) trigger
GATE 2: CHH (note 46) trigger
3 sur 5 19/01/2018 à 15:52
Page 4
Mutable Instruments | CVpal - User manual
https://mutable-instruments.net/archive/cvpal/manual/
Same as Channel 10, but with gates instead of triggers.
In these modes, the CVpal behaves like a classic monophonic CV-Gate converter implementing most recent
note priority, but also outputs triggers for synchronizing modular sequencers. A clock (with variable resolution) is
sent to GATE 1; and a reset (corresponding to the MIDI ‘start’ message) is sent to GATE 2.
OUT 1: Note CV
OUT 2: Note Gate
GATE 1: Clock trigger
GATE 2: Reset trigger
The resolution of the clock trigger depends on the MIDI channel used: 24 ppqn for channel 12; 8 ppqn for
channel 13; 4 ppqn for channel 14.
Note: Yamaha and Roland have defined different schemes for numbering octaves – and since then nobody ever
agreed on this! If, in the following procedures, everything appears to be off by one octave (the manual says
something will happen with C4 but it happens with C3) or if measurements are off by +/-1V, don’t panic – it is
simply that your controller/DAW uses a different scheme for numbering octaves.
To ensure accurate note conversion, the CVpal needs to be manually calibrated. A digital multimeter with a
precision of at least 3 digits is recommended for this task; but the calibration can also be done with an already
calibrated synth or VCO module. OUT 1 is calibrated by sending note messages to channel 15. OUT 2 is
calibrated by sending note messages to channel 16. Play a F#2 note (MIDI note 42). Check that the output
voltage is 0.500V (or that the pitch of the emitted note on the synth/VCO is correct). If this is not the case, use
F1 and G1 to make adjustments. Play a C3 note (MIDI note 48). The target voltage is 1.000V. Use B1 or C#2 to
make adjustments. Play a F#3 note (MIDI note 54). The target voltage is 1.500V. Use F2 or G2 to make
adjustments. Play a C4 note (MIDI note 60). The target voltage is 2.000V. Use B3 or C#3 to make adjustments.
Play a F#4 note (MIDI note 66). The target voltage is 2.500V. Use F3 or G3 to make adjustments. Play a C5 note
(MIDI note 72). The target voltage is 3.000V. Use B3 or C#4 to make adjustments. Play a F#5 note (MIDI note
78). The target voltage is 3.500V. Use F4 or G4 to make adjustments. Play a C6 note (MIDI note 84). The target
voltage is 4.000V. Use B4 or C#5 to make adjustments. The following chart summarizes this:
4 sur 5 19/01/2018 à 15:52
Page 5
Mutable Instruments | CVpal - User manual
https://mutable-instruments.net/archive/cvpal/manual/
Technical note: to get maximum accuracy, it is recommended to temporarily connect a 100k resistor between the
output being calibrated and ground. By doing so, the output protection resistor is taken into account. Not doing
so might cause tuning errors of up to 10 cts at either ends of the scale.
5 sur 5 19/01/2018 à 15:52
Loading...