Mutable Instruments CVpal User Manual

Mutable Instruments | CVpal - User 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.

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

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Mutable Instruments | CVpal - User manual

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

This mode is enabled when a MIDI message is received on channel 5. The CVpal behaves like a
duophonic CV-Gate 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

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