Frap Tools CGM Manuale utente

MANUALONE

A Single, Comprehensive Guide to Frap Tools’ Modules

I’d like to thank a few precious friends for their support during these years, for the discussions we had, and for the

valuable feedback i received — in alphabetical order: Tina Aspiala, Caterina Barbieri, Sebastian Baumann, Alessandro

Bonino, Marco Ciccotti, Enrico Cosimi, Lorenzo Florissi, Tom Hall, René Margraff, Gianfranco Marongiu, Chris

Meyer, Giulio Saltini, Alessio Santini, Stephan Schmitt, Brian Smith, Trevor Tunnacliffe, Giona Vinti, Andreas Zhu-

kovsky.

And thanks to the amazing people I’m working with — in alphabetical order: Fabrizio Benatti, Federico Foglia, Gio-

vanni Grandi, Antonio Masiero. Simone Fabbri

Rev. 7 – Aug 2021 Page 3 of 107

TABLE OF CONTENTS

TABLE OF CONTENTS..........................................................................3

SAFETY AND WARRANTY..................................................................6

BEFORE STARTING ...............................................................................7

1Connecting the Power............................................................... 7

2Mounting the Module ................................................................ 7

3Warm-Up and Working Temperature............................ 7

MODULAR SYNTHESIS: CORE CONCEPTS ................................8

1Voltage (and Current)................................................................. 8

2DC And AC.......................................................................................... 8

3Audio and CV.................................................................................... 8

4Timing Pulses................................................................................... 9

5Polarity .................................................................................................. 9

6Audio and CV Processing ........................................................ 9

7Audio Levels ...................................................................................10

SUGGESTED READINGS ..................................................................10

INTERFACES..........................................................................................12

1Arrows (Input, Output)............................................................12

2Square and Round Shapes..................................................12

3Lines (Solid, Dotted, Dashed).............................................12

4Color Coding ..................................................................................13

5Combinations................................................................................13

CGM – CREATIVE MIXER SERIES .................................................14

1Philosophy and Design ..........................................................15

2The Link System ..........................................................................15

Linking Groups and Channels...........................................15

2.1.1 Older Group-to-Channel Link Cables...........................15

Linking Masters and Groups...............................................15

2.2.1 Older Master-to-Group Link Cables...............................16

3Channel..............................................................................................16

Amplitude Controls and Direct Output......................16

Effect Sends....................................................................................16

Pan........................................................................................................16

Creative Functions.....................................................................16

3.4.1 Mute.....................................................................................................16

3.4.2 Solo in Place ...................................................................................16

3.4.3 PFL ........................................................................................................17

4Quad Stereo Channel ..............................................................17

Amplitude Controls and Direct Output......................17

4.1.1 Mono Auxiliary Input................................................................17

Pan and Crossfade.....................................................................17

4.2.1 Pan........................................................................................................17

4.2.2 Crossfade..........................................................................................17

Creative Functions.....................................................................17

4.3.1 Mute.....................................................................................................17

4.3.2 Solo in Place ...................................................................................18

4.3.3 PFL ........................................................................................................18

5Group...................................................................................................18

Amplitude Control.....................................................................18

Effect Sends/Returns ...............................................................18

5.2.1 Sends...................................................................................................18

5.2.2 Returns...............................................................................................18

Group Output................................................................................18

5.3.1 Group Jumpers Congurations .......................................18

Creative Functions.....................................................................19

5.4.1 Group Mute.....................................................................................19

5.4.2 Safe Solo............................................................................................19

5.4.3 PFL ........................................................................................................19

6Master (Discontinued).............................................................19

Amplitude Control.....................................................................19

Auxiliary Stereo Input ..............................................................19

Creative Functions.....................................................................19

6.3.1 Headphones................................................................................... 19

6.3.2 PFL........................................................................................................19

7Masterone........................................................................................ 20

Amplitude Control.....................................................................20

7.1.1 Pseudo-balanced TRS Outputs........................................20

7.1.2 Balanced XLR Outputs...........................................................20

7.1.3 Mono Out.........................................................................................20

Creative Functions..................................................................... 20

7.2.1 Headphones................................................................................... 20

7.2.2 PFL........................................................................................................21

8Technical Data.............................................................................. 22

Flow Charts.....................................................................................22

Specications................................................................................24

SAPÈL.......................................................................................................25

1Philosophy and Design..........................................................25

2Noise Outputs............................................................................... 26

3Voltage Sampling....................................................................... 26

Internal Clock and Clock Modulation .......................... 26

External Clock............................................................................... 26

Clock Mix...........................................................................................26

Manual Sampling....................................................................... 27

External Gate Sampling.........................................................27

Clock Outputs (Main and Random) .............................. 27

4Random Voltages....................................................................... 27

Non-Quantized Random Voltages ................................27

Quantized Random Voltages ............................................ 27

Fluctuating Random Output and Global Rate of

Change (random clock density control).................... 28

5Probability Distribution (Stored Random Voltages)

................................................................................................................. 29

6Technical Data.............................................................................. 30

Flow Chart ....................................................................................... 30

Specications................................................................................30

FUMANA..................................................................................................31

1Philosophy and Design..........................................................31

Spectral Transfer: A Brief History..................................... 32

Panel Overview............................................................................ 32

2Audio Inputs................................................................................... 32

3Audio Outputs.............................................................................. 33

4Audio Processing and Modulation Path.................... 33

Faders and CV............................................................................... 33

Macro Spectral Editing...........................................................34

4.2.1 Tilt..........................................................................................................34

4.2.2 Parametric Scanning............................................................... 34

Spectral Transferring: Modulation Filters and

Envelope Followers................................................................... 34

The ‘Unvoiced’ Section............................................................35

5Filter Design................................................................................... 36

6Patch Examples........................................................................... 36

16-Band Spectral Transfer...................................................36

Dual 8-Band Spectral Transfer ......................................... 36

Hybrid Spectral Transfer........................................................36

Vocoder-Like Behavior ........................................................... 37

7Technical Data.............................................................................. 37

Transfer Function....................................................................... 37

Specications................................................................................38

FALISTRI..................................................................................................39

1Philosophy and Design..........................................................39

2Function Generators................................................................ 39

Times................................................................................................... 40

Shapes................................................................................................40

Trig and Modes ............................................................................ 40

2.3.1 Green Alternative Retrig (On Rest) ................................41

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Outputs..............................................................................................41

Additional Generator Features .........................................41

2.5.1 Quadrature......................................................................................41

2.5.2 Max........................................................................................................42

2.5.2.1 ADSR....................................................................................................42

3Function Processors.................................................................42

Dual Cascaded Frequency Divider.................................42

Four-Quadrant Multiplier .....................................................43

3.2.1 Amplitude Modulation & Ring Modulation (2 vs 4

quadrants) .......................................................................................43

3.2.2 Trimming..........................................................................................44

Linear Slew Limiter....................................................................44

4Technical Data..............................................................................45

Specications................................................................................45

Revisions ...........................................................................................45

USTA .........................................................................................................46

1Quick start .......................................................................................46

2Philosophy And Design..........................................................47

Architecture....................................................................................47

Tempo Management...............................................................47

3Basic Editing and Visual Feedback ...............................48

Editing Projects − Project Menu......................................48

Editing Tracks − Track Menu ..............................................49

3.2.1 Clock Settings...............................................................................49

Editing, Playing and Looping Patterns.......................49

Editing Stages...............................................................................50

3.4.1 Length ................................................................................................51

3.4.2 Maintain Pattern Length on Variation ........................51

3.4.3 CV Layers..........................................................................................51

3.4.3.1 Red CV Layer: Value.................................................................. 52

3.4.3.2 Green CV Layer: Variation Index ......................................52

3.4.3.3 Blue CV Layer: Variation Range........................................53

3.4.4 CV Stage Colors............................................................................53

3.4.4.1 USTA Slide vs FALISTRI Slew...............................................53

3.4.5 Gate Layers......................................................................................54

3.4.5.1 Red Gate Layer: Value..............................................................54

3.4.5.2 Green Gate Layer: Variation Index..................................54

3.4.5.3 Blue Gate Layer – Variation Range.................................54

3.4.6 Gate Stage Colors.......................................................................54

4Quick Editing.................................................................................55

Set All and Shift All.....................................................................55

Coarse and Fine ...........................................................................56

Combining the Buttons.........................................................56

5Performing......................................................................................56

Play/Pause, Reset and Master Track Settings........56

5.1.1 Master Track...................................................................................56

5.1.2 Play/Pause .......................................................................................57

5.1.3 Reset....................................................................................................57

Stage Loop.......................................................................................57

5.2.1 Innite Stage Loop....................................................................58

Song Mode......................................................................................58

5.3.1 Pattern to song while playing (and vice versa).....59

Live Performance Tools: Pattern Recall......................59

5.4.1 Full pattern recall........................................................................60

5.4.2 Pattern Mix......................................................................................60

Mute.....................................................................................................60

5.5.1 Mute Track.......................................................................................60

5.5.2 Mute Channel................................................................................60

Hold ......................................................................................................60

6Advanced Editing.......................................................................61

Composition Mode....................................................................61

Use an External CV/Gate Keyboard...............................61

Store Pattern: Last Played or Last Full.........................62

Rotate Pattern ..............................................................................62

Cloning...............................................................................................62

6.5.1 Clone a Stage.................................................................................62

6.5.2 Clone a Structure........................................................................63

6.5.2.1 Clone a Layer................................................................................. 63

6.5.2.2 Layer Cross-Cloning.................................................................. 63

6.5.2.3 Clone a Pattern............................................................................ 63

6.5.2.4 Clone a Track................................................................................. 64

Quick Track Initialization....................................................... 64

Quick Song Initialization ....................................................... 64

7External Controls ........................................................................ 64

Clock Input......................................................................................64

Auxiliary Trig/Gate Input ....................................................... 64

7.2.1 Reset.................................................................................................... 64

7.2.2 Run........................................................................................................65

External CV......................................................................................65

7.3.1 Pitch Shift.........................................................................................65

7.3.2 Root Shift..........................................................................................65

7.3.3 Gate Shift..........................................................................................65

7.3.4 Stage Shift ....................................................................................... 65

7.3.5 Vari Shift (Variation Shift)...................................................... 66

7.3.6 Pattern Shift................................................................................... 66

7.3.7 Phase Shift....................................................................................... 66

8Additional Operations.............................................................67

Select CV Mode (Raw or Pitch)......................................... 67

CV Range.......................................................................................... 67

Gate Width %................................................................................. 67

Swing...................................................................................................67

Current Stage Data...................................................................68

9Playing in Tune ............................................................................ 68

Root & Scale – Dynamic Quantization......................... 68

Microtonalities.............................................................................. 69

Custom Scales..............................................................................69

Set the Reference Note.......................................................... 70

Custom Temperaments ........................................................ 70

9.5.1 Absolute or Relative Temperaments............................ 70

LED Pitch Tables ......................................................................... 72

10 Additional Maintenance........................................................ 74

Remove / Insert the SD Card..............................................74

10.1.1 Remove the SD Card................................................................ 74

10.1.2 Insert the SD Card......................................................................74

Analog Trimming ....................................................................... 74

10.2.1 CV Out Trimming ....................................................................... 74

10.2.2 CV In Trimming............................................................................74

Project Management and Backups.............................. 74

Firmware Update....................................................................... 75

11 CHARTS..............................................................................................76

Project Menu................................................................................. 76

Track Menu.....................................................................................76

Project Hierarchy........................................................................77

12 Scale Tables....................................................................................78

13 Change Log....................................................................................85

14 Technical Data.............................................................................. 85

Specications................................................................................85

BRENSO...................................................................................................86

1Philosophy, Design and Signal Flow ............................ 87

2Frequency........................................................................................87

Oscillators.........................................................................................87

2.1.1 Fine and Coarse Tuning.........................................................87

2.1.2 Coarse Frequency Lock.......................................................... 87

2.1.3 V/oct and Integrator................................................................. 88

Frequency Modulation........................................................... 88

2.2.1 FM Routing.....................................................................................89

Sync......................................................................................................89

2.3.1 Lock...................................................................................................... 90

2.3.2 Flip Sync............................................................................................ 90

3Timbre ................................................................................................90

Triangle Shaper............................................................................ 91

Pulse Shaper..................................................................................91

3.2.1 Pulse-Width Modulation (PWM)..................................... 91

3.2.2 Waveshaper ...................................................................................92

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Wavefolder......................................................................................92

3.3.1 Sources...............................................................................................92

3.3.2 Folding ...............................................................................................92

3.3.3 Symmetry.........................................................................................93

3.3.4 Ping ......................................................................................................93

Timbre Modulation Bus .........................................................93

4Amplitude........................................................................................94

Amplitude Modulation and Ring Modulation........94

5Trimmers ..........................................................................................94

Accessible Trimmers ................................................................94

5.1.1 Coarse Frequency ......................................................................94

5.1.2 Sine Wave Symmetry ..............................................................95

5.1.3 Sawtooth Wave Symmetry..................................................95

5.1.4 Exponential FM Zero................................................................95

5.1.5 Triangle Waveshaper Shape...............................................95

5.1.6 Wavefolder Symmetry............................................................95

5.1.7 Four-Quadrant Multiplier .....................................................95

5.1.8 Comparator.....................................................................................95

Non-Accessible Trimmers ....................................................95

5.2.1 Gain.......................................................................................................95

5.2.2 Base......................................................................................................95

5.2.3 Symmetry.........................................................................................95

6Technical Data..............................................................................96

Simple Signal Flow....................................................................96

Specications................................................................................97

Revisions ...........................................................................................97

333 ............................................................................................................98

1Design.................................................................................................98

2Technical Data.............................................................................. 99

Flow Chart ....................................................................................... 99

Specications................................................................................99

321 .........................................................................................................100

1Design .............................................................................................100

2Technical Data...........................................................................101

2.1.1 Flow Chart ....................................................................................101

2.1.2 Specications.............................................................................101

PLUS.......................................................................................................102

1PHILOSOPHY AND DESIGN.............................................102

Units..................................................................................................102

1.1.1 Closed ..............................................................................................102

1.1.2 Windowed....................................................................................102

Sides..................................................................................................103

1.2.1 Thick Sides....................................................................................103

1.2.2 Thin Sides......................................................................................103

2Purchase Options....................................................................103

3ASSEMBLY INSTRUCTIONS..............................................103

Single Unit to Wooden Sides..........................................103

Single Unit to Aluminum Sides.....................................103

Single Unit to Single Unit ..................................................104

Single Windowed Unit to Single Windowed Unit

(Row Extension)........................................................................104

WHAT’S IN THE BOX ......................................................................105

LIST OF REVISIONS .........................................................................107

Rev. 7 – Aug 2021 Page 6 of 107

SAFETY AND WARRANTY

The Frap Tools srls warranty covers the

following products (hereinafter ‘Frap

Tools’), for two (2) years following the date

of purchase. This warranty covers any de-

fect in the manufacturing of this product.

This warranty does not cover any damage

or malfunction caused by incorrect use as

described in the following instructions.

The warranty covers replacement or re-

pair, as decided by Frap Tools. Please con-

tact customer service at [email protected]ls

for a return authorization.

Frap Tools warrants that your new Frap

Tools product, when purchased from an

authorized Frap Tools dealer, shall be free

of defects in materials and craft for a pe-

riod of two (2) years from the original date

of purchase. Please contact Frap Tools for

warranty and service outside of Europe.

During the warranty period, Frap Tools

shall, at its sole option, either repair or re-

place any product that proves to be defec-

tive upon inspection by Frap Tools. Frap

Tools reserves the right to update any unit

returned for repair and to change or im-

prove the design of the product at any time

without notice. This warranty can be

transferred to anyone who may subse-

quently purchase the product provided

that such transfer is made within the ap-

plicable warranty period and that Frap

Tools is provided with all of the following

items:

·all warranty registration information

for the new owner;

·proof of the transfer within thirty (30)

days of the transfer purchase, and a pho-

tocopy of the original sales receipt.

Frap Tools shall determine warranty

coverage in its sole discretion: this is your

exclusive warranty. Service and repair of

Frap Tools products are to be performed

only by Frap Tools or an authorized ser-

vice company. Unauthorized service, re-

pair, or modification will void this war-

ranty.

Please follow the given instructions for

the use of the device because this will guar-

antee the correct device operation. Since

these instructions also include indications

concerning Product Liability, they must

be read carefully. Any claim for defect will

be rejected if one or more of the following

points is not observed. Any disregard of

these instructions can void the warranty.

The devices may only be used for the

purpose described in this operating man-

ual. Due to safety reasons, the devices

must never be used for purposes not de-

scribed in this manual. If you are not sure

about the intended purpose of the devices,

please contact an expert or Frap Tools at

the email address above.

Do not use or store the devices in humid

places. Avoid contact with any liquid.

Do not touch any component of the de-

vices when it is power or connected to any

power source.

Do not place the devices on unstable

carts, stands, tripods, tables, or other sur-

faces, or on surfaces that are not perfectly

plane. Such behavior may cause the de-

vices to fall, which could result in human

injury, property damage or improper

functioning of the devices themselves.

The devices are designed for use only

when safely and tightly mounted in a

proper Eurorack case, made of non-flam-

mable materials. If you are not sure about

the intended purpose of the devices, please

contact an expert or Frap Tools at the

email address above.

Do not ever leave the devices switched

on when not in use.

To prevent fire, never place any candle,

flame, or other sources of heat on or near

the devices.

Transport the devices only in the origi-

nal box with original packaging or when

safely and tightly mounted in a proper Eu-

rorack case and handled with care. Never

let the devices fall or topple. Make sure

that during transport and while in use the

devices and their case, have a proper stand

and do not fall, slip or turn over because

of potential human injury to persons or

property damage. Any damage from phys-

ical abuse such as dropping the unit, im-

pact from hard objects or damage to ex-

ternal components as a result of negli-

gence will void this warranty.

Never expose the devices to tempera-

tures above +40°C or below 0°C.

Before any operation, also verify the op-

erating temperature ranges of all the mod-

ules and the power boards in use. Do not

keep or leave the case that hosts the de-

vice, or the devices themselves near heat

sources.

Any modification must be carried out

only by Frap Tools or an authorized ser-

vice company. The devices may not be

modified in any way by any parties not ex-

pressly authorized by Frap Tools. Any re-

pair, modification, tampering, or at-

tempted repair made by unauthorized

personnel will void this warranty.

Frap Tools cannot be held responsible in any

way for problems to persons or property or to

the devices themselves, if the devices are

installed improperly, or if they are improperly

used, maintained, or stored.

Any device shipped to Frap Tools for re-

turn, exchange, warranty repair, update,

or examination must be sent in its original

packaging! Any other deliveries will be re-

jected. Therefore, you should keep the

original packaging, and any technical doc-

umentation or manual provided. The de-

vice must be shipped only with the original

packaging. As specified on the product

box, this box is not intended for shipment:

if you bought the device directly at a phys-

ical reseller’s shop, you should put the de-

vice in the original packaging and put the

packaging in a properly larger box with

proper packaging destined for shipping. If

you received the device via carrier or any

post service, it should have come with a

proper double box packaging.

All non-warranty services are subject to

a minimum fee of €50.00+VAT (within

the European Union). The customer must

pay for shipping to Frap Tools; Frap Tools

will cover return shipping costs.

It is important to note that the front

panel of our modules may get warm and

may warm up the case where it is

mounted. Please do not be alarmed, as this

is normal and is part of its standard oper-

ation.

Shut down your equipment immediately

if it produces smoke, a strange odor, or un-

usual noise. Continued use may lead to

fire. Immediately unplug the equipment

and contact your dealer or Frap Tools at

the address above for advice.

Never attempt to repair this product

yourself. Improper repair work can be

dangerous. Never disassemble or modify

this product. Tampering with this product

may result in injury or fire and will void

your warranty.

Do not allow foreign matter to fall into

the equipment. Penetration by foreign ob-

jects may lead to fire.

If water or other liquid spills into this

equipment, do not continue to use it. Con-

tinued use may lead to fire. Unplug the

power cord immediately and contact your

dealer or Frap Tools at the address above

for advice.

The internal components of our mod-

ules and power supplies can get very hot.

Do not touch any internal components

while it is connected and/or powered and

after they completely cool down after use

for at least 30 minutes.

Rev. 7 – Aug 2021 Page 7 of 107

BEFORE STARTING

1CONNECTING THE POWER

To connect the power cable, carefully follow these two

rules:

·the power connector on the module is the keyed one

in the top;

·the red line on the cable should be placed matching

the −12 V side on your power board: please double check

with your power boar supplier that the marked side is the

−12 V.

Frap Tools may not be held responsible in any way for prob-

lems or damage to persons or property or to the device itself,

if the device is not connected as indicated above.

2MOUNTING THE MODULE

After connecting the power as explained in the previous

section, install the module in your case using all the 2 or

4 screws provided. Make sure that the module is safely

and tightly connected to your Eurorack case.

Frap Tools modules use the standard Eurorack orienta-

tion and color-coding: the red line on the power cables is

placed at the bottom and stands for the −12 V. Please

double check with the power system you want to use that

it adopts the same powering system.

Frap Tools may not be held responsible in any way for prob-

lems or damage to persons or property or to the device itself,

if the device is not connected as indicated above.

Figure 1: Power connection.

3WARM-UP AND WORKING TEMPERA-

TURE

For best performances, we suggest letting the Frap

Tools modules warm up at least around 20 minutes prior

to use it [tested at 25°C]. It is absolutely normal that they

feel warm when touched.

Rev. 7 – Aug 2021 Page 8 of 107

MODULAR SYNTHESIS: CORE CONCEPTS

In this introduction we’ll go through the basics of ana-

log modular synthesizers in their broader meaning, to

make sure that all the technical jargon that we’ll be inev-

itably using throughout the manual will be, hopefully,

clarified for the newcomers.

Modules in a modular synthesizer can be thought of as

strangers sitting next to each other on a train compart-

ment, sitting in an embarrassed silence.

Creating music from a modular synthesizer is like start-

ing a conversation on our hypothetical train compart-

ment, by connecting modules with patch cables and mak-

ing them “speak” to each other.

For any conversation to happen we need two things: the

people must have something to say (like an argument),

and they must speak the same language.

In modular synthesizers, the argument is your musical

idea, and it is beyond the scope of this manual, while the

common language to make your modules communicate

is the voltage.

1VOLTAGE (AND CURRENT)

Even though this is not an engineering manual, a gen-

eral introduction on the concept of voltage might be use-

ful to better understand how these instruments work.

Voltage is the difference in electric potential between

two points of a circuit, or, oversimplifying, «what you ap-

ply to cause currents to flow.»

It is measured in volts,

whose symbol is V. Without any other specification, the

voltage is calculated between any point of the circuit and

a reference point called ground (0 V).

Electric potential brings in the concept of current, which

is the actual flow of electric charge through a circuit.

Electric charge is measured in coulomb (C), while the

current is measured in amperes (A): 1 ampere equals to 1

coulomb of charge passing through a given point in 1 sec-

ond.

Enough for the technical stuff: now it’s time to see how

voltage and current turn into (electronic) music.

2DC AND AC

There are two kinds of current, each of which implies a

different kind of voltage. They are direct and alternating cur-

rent, abbreviated DC and AC respectively, and we use

both in modular synthesizers.

In case of direct current, our charge flows only in one

direction: if the current is steady, so will do the voltage.

This kind of fixed voltages are what we use, for example,

to send note information to the sound source.

(Horowitz 2019, 1, note 2.)

In case of alternate current, our charge flows back and

forth in our circuit. Its alternation over time can be dis-

played with a waveform diagram. In case of alternate cur-

rent, the voltage changes over time as well. We use this

kind of varying voltages to generate, for example, wave-

forms that ultimately will turn into sound.

3AUDIO AND CV

To hear music, we need some vibrating air. To make

the air vibrate, we need a vibrating body: we can pluck a

string, hit two wood sticks, blow into a pipe and so on.

In case of electronic instruments, our vibrating body is

the loudspeaker (or the headphones).

More in detail, in the specific case of analog modular

synthesizers, everything, from the sound generation, to its

articulation, to the final audio output through the speaker

cone’ vibration, is achieved through voltage that change

over time.

With our modular synthesizer we create a complex,

electric signal that makes our cones move back and forth.

The variation of voltage over time translates into the

complex waveform that we call music.

It goes without saying that the more control we have

over our voltage, the more expressive and articulated will

become our composition’s waveform.

In modular synthesizers, we use voltage to generate

sound, but also to control it.

If a circuit generates a voltage that varies from, say, -

5V to 5 V, 110 times a second, it will make our loud-

speaker vibrate as many times, thus producing a sound

whose frequency is 110 Hertz (Hz), corresponding to the

note A.

However, if the same circuit generates a voltage oscilla-

tion of 10Hz, meaning that the voltage varies from -5 to

5V ten times a second, we wouldn’t be able to hear it

anymore. It’s because its frequency is below our audible

range of human beings, that spans from 20 to 20.000Hz.

This brings in a conventional distinction between volt-

ages that we use for sound generation, which provide alter-

nate current in the audio range, and voltages that we use

for sound modulation or control, which are often called con-

trol voltages, or CV. Generally speaking, we use CV to turn

our modules’ knobs for us, in a sort of automated way.

CVs can be of any kind: they can generate alternate

current, such as low-frequency oscillators (LFOs, like the

ones we use for tremolo effects) or direct current (like the

fixed CVs that we use to send pitch information).

Rev. 7 – Aug 2021 Page 9 of 107

It is nice to point out that in modular synthesis we use

the same two or three principles to take care of every pa-

rameter of the sound design.

4TIMING PULSES

We use CV to distribute information (like pitch, ampli-

tude, timbre) all over our electronic composition.

For example, the information of “C#4” is not enough

to generate a note: it generates just a pitch. To have a

note, we need to give it some timing: when it begins, how

long it lasts, when it ends.

For this kind of information, which is essential to define

any kind of musical event (note, melody, rhythm), we use

a particular kind of CV called timing pulses, which are trigs

and gates.

Trigs and gates are pulses, because they can have only

two values, off and on, and because the transition be-

tween one value and the other is almost immediate. Off is

usually 0 V, on is around 5 V.

The main difference between trigs and gates is that trigs

are very fast voltage bursts that go from 0 to 5 V and im-

mediately (actually, after one or two milliseconds) back to

zero, while gates can stay at 5 V as much as we want.

A trig is thus a timing pulse that defines when a certain

musical event should happen, while a gate is a timing

pulses that tells when such an event should happen, but

also exactly for how long.

Trigs are the kind of pulses that we get out of clock gen-

erators, such as SAPÈL, while gates are generated by

modules such as FALISTRI or USTA, which are more

focused on articulation and dynamics.

5POLARITY

We have said that voltage is a difference in electric po-

tential that causes the current to flow through a circuit.

Such a current can flow through a point in either direc-

tion, depending on the voltage that we apply to the cir-

cuit. A positive voltage will make the current flow in a

direction, and a negative one in the opposite. (0 V will not

have any current flow, and such is the value of the cir-

cuit’s ground.)

In case of alternating current, the voltages are also al-

ternating. If such alternation oscillates above and below

0V, the voltage would be bipolar. However, there are

cases in which the change in voltage is only positive (or,

more rarely, negative). In such cases, we say that the volt-

age is unipolar.

The most common bipolar voltages are the ones used

for generating audio waveforms, since they need to move

the speaker’s cone back and forth. A unipolar audio

On the importance of parametrical thinking when approaching analog

sound design, see especially (Strange 1984, 4–5).

signal would make the cone move in one direction only,

with potential damages.

Unipolar voltages are, for example, certain envelopes,

or LFOS, especially the ones used for controlling a pa-

rameter which needs to operate in one direction only,

such as amplifiers (on which see the next chapter).

6AUDIO AND CV PROCESSING

In modular synthesis, we add dynamics and expressive-

ness to our music through signal processing. We use quite

a few concepts, but their combination provides many dif-

ferent results.

The most important element of signal processing is the

control over a signal’s amplitude. Amplitude is, roughly,

how loud we perceive the sound, which means how much

the air vibrates, which also means how much our speaker

cones vibrate, which, in turn, means how high is the volt-

age oscillation that we generate with out synthesizer.

Controlling the amplitude of a signal means being able

to define the voltage range of our sound source, which is

bipolar: for example, an amplitude of 5 V means that our

waveform will go from 0 V to 5 V, and then from 0 V to

-5v throughout each cycle. Since there is a difference of

10 V from 5 V to -5 V, we can also say that our signal has

an amplitude of 10 V peak-to-peak (Vpp), i.e., measured

from the highest to the lowest point of the waveform cycle

(“peaks”).

There is another way of measuring a signal’s amplitude,

and it’s the root-mean-square amplitude (rms). In elec-

tronics, this concept is useful because it expresses the the

value of a periodic signal (like alternating current) as if it

were a constant signal of equal average power (like direct

current).

It is not necessary to dive too much into this

concept now, but we needed to introduce it because we’ll

refer to Vrms values in the next section about signal levels.

The circuit that allows us to control the amplitude is

called amplifier: increasing or decreasing the amplifier

value, usually through a knob, increases or decreases the

amplitude of our sound, and eventually brings it to 0 V,

where no sound is passing through the circuit. An ampli-

fier is often capable of increasing a signal’s amplitude,

thus providing a louder sound than the one generated by

our sound source. A circuit that only reduces a signal’s

amplitude is often called attenuator.

Furthermore, amplifiers can also deal with signals that

are not waveforms, such as control voltages. In this case,

amplifiers control the voltage magnitude, and they can

make controls sources and their modulations more or less

effective in a patch.

An amplifier that is we can control through voltage is

called VCA, voltage-controlled amplifier. For example, if

(Strange 1984, 51–52, 61–62)

(Horowitz 2019, 14)

Rev. 7 – Aug 2021 Page 10 of 107

we control an amplifier with an LFO, this will cyclically

increase and decrease the signal’s amplitude, like a trem-

olo effect. But we can also control the LFO’s amplitude

through a second VCA, and now it will change the mod-

ulation depth.

Another useful concept to outline now is inversion, which

relies on the fact that voltages, in Eurorack synthesizers,

can be positive or negative. Inverters are circuits that

change the polarity of a given signal: on a graphical rep-

resentation, the result of an inverted continuous voltage

will be a mirrored, upside-down version of the original

signal.

If the signal is bipolar, the positive values will become

negative, and vice-versa.

We can also invert audio signals, and in such case, we’ll

invert their phase.

7AUDIO LEVELS

In the previous section, we said that a sound’s ampli-

tude is related to how loud or soft we perceive it. Loud-

ness, however, is a tricky value because it always needs to

be measured against a reference point. Since the human

ear is sensitive to dramatic pressure changes, to measure

such changes it is always used a logarithmic unit called

decibel (dB).

Audio equipment marks with 0 dB the “reference

value,” which is usually the point at which the signal can

get the maximum strength without distorting. However,

many circuits allow us to increase the sound loudness be-

yond 0 dB: the range where we can push our sound is

called headroom, and usually stretches at least until 12 dB.

Since the dB is a relative unit, the 0 dB level can change

from device to device. For this reason, such a reference

value is often calculated on the circuit’s absolute voltage

rms amplitude (see the previous section). There are some

Vrms values that have now become standars, for example:

Equipment

0dB amplitude

Consumer/Hi-Fi equipment (often with RCA

connectors)

300 mVrms

Professional equipment

1.228 Vrms

Eurorack synthesizers

3.535 Vrms

Table 1: Common 0 dB Reference Values

The Eurorack Vrms value is calculated on a sine wave of

10 Vpp, i.e., a bipolar signal of +/– 5 V.

A circuit’s headroom depends on the equipment’s

power source. In the case of Eurorack systems, the avail-

able voltage is less than +/–12 V, for a total of 24 V; stu-

dio equipment is usually between +/–15 V (30 V total)

and +/–18 V (36 V total), with some rare cases even be-

yond +/–24 V (48 V total).

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