Frap Tools CGM User manual

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

Rev. 7 – Aug 2021 Page 5 of 107
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.»
1
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.
1
(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.
2
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.
3
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
2
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).
4
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
3
(Strange 1984, 51–52, 61–62)
4
(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).
5
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).
SUGGESTED READINGS
Bernstein, David W. The San Francisco Tape Music Center. 1960s Counterculture and the Avant-Garde. Berkeley: University of California Press, 2008.
Bjørn, Kim. Patch & Tweak. Exploring Modular Synthesis. Copenhagen: Bjooks, 2018.
Bode, Harald. “History of Electronic Sound Modification.” AES: Journal of the Audio Engineering Society 32, no. 10 (1984).
Chowning, John M. “The Synthesis of Complex Audio Spectra by Means of Frequency Modulation.” AES: Journal of the Audio Engineering Society 21, no. 7
(1973): 526–34.
https://web.eecs.umich.edu/~fessler/course/100/misc/chowning-73-tso.pdf
Hordijk, Rob. “Designing Instruments for Electronic Music.” EContact! 17, no. 4 (2016).
https://econtact.ca/17_4/hordijk_design.html
Horowitz, Paul. The Art of Electronics. Third edition. New York: Cambridge University Press, 2019.
Roads, Curtis. The Computer Music Tutorial. Cambridge, MA-London, 1996.
Shapiro, Peter. Modulations. A History of Electronic Music. Throbbing Words on Sound. New York: Caipirinha Productions, 2000.
Strange, Allen. Electronic Music: Systems, Technics, and Controls. Second edition. Dubuque: Brown, 1984.
Wells, Thomas. The Technique of Electronic Music. Second edition. New York-London: Schirmer Books-Collier MacMillan, 1981.
5
For a description of the decibel units, see (Strange 1984, 142–143; Hor-
owitz 2019, 15)

Rev. 7 – Aug 2021 Page 11 of 107

Rev. 7 – Aug 2021 Page 12 of 107
INTERFACES
Here at Frap Tools, we put a lot of effort into designing
a proper user interface for each of our modules.
By “proper user interface” we mean essentially three
things:
1. it must convey the module’s identity at a glance;
2. it must allow for a smooth creative workflow;
3. it must be pleasant to look at.
Moreover, we want our interfaces to be clear, but not
self-explanatory (or, in other terms, cryptic, but not cha-
otic).
The reason for doing so is that, in our vision, the musi-
cian should master the “code” of the instrument before
playing it: a piano does not have the note names on its
keys, a violin does not have marks on its neck — it is up
to the musician to practice and learn how the instrument
works.
In the same way, our modules do not have labels such
as ‘frequency’ or ‘decay time’: instead, they are replaced
with a system of symbols and colors that try to be as con-
sistent as possible. Moreover, a musician approaching
our modules through a “conventional” labeling system
might be tempted to assume that the module behaves in
an ordinary way, which sometimes is not completely cor-
rect.
The modules are explained in detail further in this man-
ual. However, to allow the musician to get acquainted
with the overall symbol system, we provide here a brief
guide to “decode” the most recurrent elements of the
“Frap environment”.
1ARROWS (INPUT, OUTPUT)
An arrow can mean either an input or an output, ac-
cording to its position: if it points towards one or more
jack sockets, it is an input; if it points away from one or
more jack sockets, it is an output.
Figure 2: Arrows.
2SQUARE AND ROUND SHAPES
All the modular world revolves around voltage. The
most basic distinction is, conventionally, between voltage
used for timing pulses (trigs or gates) and voltage used for
audio signals or CV.
The former is a discrete signal with two levels only (“off”
and “on”, “low” and “high”). In our modules it is
associated with square shapes: the reason is that squares
have only two kind of lines (vertical and horizontal), in
the same way a gate or rig signal has only two possible
states, on and off.
Figure 3: Square shapes.
The latter is a continuous signal (or ‘analog’ in its clos-
est meaning). Is associated with round shapes because cir-
cles can be thought of as having infinite sides, in the same
way an analog signal has infinite values.
Figure 4: Round shapes.
A subgroup of audio analog section is the stereo audio.
As you can notice in the CGM series, the group and mas-
ter modules feature stereo in and out out: here, the
left/mono is connected to the solid-colored area, while
the right is connected to the ring that surrounds it. The
reason is that the left output is always the primary (be-
cause it can be used as a mono output as well), while the
right one is more of an accessory to it.
Figure 5: Stereo audio.
3LINES (SOLID, DOTTED, DASHED)
A solid line relates two or more elements of the circuit.
It stands for manual control, which means that a given
knob or switch directly affects the signal passing through
the circuit from an input or to an output.
Figure 6: Solid lines.

Rev. 7 – Aug 2021 Page 13 of 107
A dotted line stands for external CV control, and it of-
ten relates a jack socket to a manual control such as a
knob or a slider. It means that the specific parameter can
be voltage controlled.
Figure 7: Dotted lines.
A dashed line relates two or more inputs or two more
outputs: it means that they are semi-normalled, or, in
other terms, that the signal going to one input or coming
from one output is mirrored by the other jack sockets con-
nected by a dashed line. Such behavior is automatically
overridden once a cable is plugged to another jack socket
(thus “breaking” the normalization).
Figure 8: Dashed lines.
4COLOR CODING
As a rule of thumb, if a module performs more than one
function, the respective controls are marked with differ-
ent colors. In other words, a given color relates to one and
only one section of the module design. In case a module
features two “mirrored” sections (such as SAPÈL’s or
FALISTRI’s generators, or CGM Group’s FX sends),
they are marked in yellow and green.
5COMBINATIONS
All the elements can be combined. For example, an ar-
row within a square pointing towards a jack socket means
that it is a gate/trig input; if a dotted line connects a jack
socket to a knob, and a solid line connects the same knob
to another jack socket, it means that the signal outputted
from the second jack socket can be modified either man-
ually via the knob or automatically via an external CV
patched to the first socket.

Rev. 7 – Aug 2021 Page 14 of 107
CGM – CREATIVE MIXER SERIES
Figure 9: CGM Interface

Rev. 7 – Aug 2021 Page 15 of 107
AMain Audio
Routing
A.1 Audio Mono Input
A.2 Audio Input
Left/Dual Mono
A.3 Audio Input
Right/Dual Mono
A.4 Direct Out
A.5 VCA Level
A.6 VCA Level CV Input
A.7 VCA Pre/Post
A.8 Pan Level
A.9 Pan Level CV
A.10 Pan/Crossfade
Switch
A.11 Channel Fader
A.12 Local Output Left
A.13 Local Output Right
A.14 Group Output Left
A.15 Group Output Right
A.16 Group Fader
A.17 Master Output Left
A.18 Master Output
Right
A.19 Master Fader
A.20 Aux. Stereo Input
A.21 Aux. Mono Input
A.22 Aux. Input Level
A.23 Phones Stereo
Output
A.24 Phones Level
A.25 Line/Inst Switch
A.26 Balanced Output
Left
A.27 Balanced Output
Right
A.28 Line/Mic Switch
A.29 Mono Out
A.30 Mono Out Fader
BSend/Return
B.1 Effect Send Level
B.2 Effect Send Level CV
B.3 Effect Send Pre/Post
B.4 Effect Send Mono
Output
B.5 Effect Return Left
Input/Dual Mono
B.6 Effect Return Right
Input/Dual Mono
B.7 Effect Return Level
B.8 Effect Return Level
CV
CCreative Functions
C.1 Mute Button
C.2 Solo-In-Place But-
ton/Switch
C.3 Safe Solo Switch
C.4 Pre-Fader Listen
(PFL) Button and
LED
C.5 PFL Blend
1PHILOSOPHY AND DESIGN
The CGM Creative Mixer is a modular mixing solution
for Eurorack systems. It breaks down the main parts of a
classic mixer console into three families of modules (chan-
nel, group, and master), without sacrificing the pro audio
quality of the signal treatment.
The CGM is designed for a performance-oriented use
in modular synthesizers: its modular structure allows for
tailoring the size and kind of the mixer to the exact setup
it must fit into, while the CV inputs over all the key pa-
rameters encourage heavy patching and modulations.
It is currently composed of four modules: the Channel,
the Quad Stereo Channel, the Group, and the Master-
one. A fifth module, the Master, is now discontinued.
2THE LINK SYSTEM
Some CGM modules, like the QSC, can efficiently
work as stand-alone units. However, they unlock their full
potential when connected to other units to build a com-
plex mixing console.
For this purpose, we designed a special set of connecting
cables named Link System, which replaces the older Link
Cables (now discontinued, but still compatible with newer
products).
There are three kinds of cables in the new Link System:
•group-to-channel cable;
•master-to-group cable;
•group-to-group extension.
Here’s how it works.
Watch the assembly instructions with many
conguration examples in the following video:
How to Build a Frap Tools CGM Eurorack Mixer
Setup
LINKING GROUPS AND CHANNELS
The first step to build a CGM configuration is connect-
ing channels to a group. This connection happens
through two special group-to-channel cables with 10-pole
IDC sockets: connect the two rows of pin headers on the
back with the two pin headers in the same position on the
group’s PCB.
The GC sockets are spaced so that they can accept
modules up to 18 HP wide. For a better fitting, we rec-
ommend folding the cables in a Ω shape.
When connected to a group, all the channels share au-
dio, power, and controls, so it is sufficient to connect to
the PSU just one channel of those linked to such group.
The GC Link System comes in three different sizes:
F-G1C2-LS
CGM Link System – 1 Group to 2 Channel Modules
F-G1C4-LS
CGM Link System – 1 Group to 4 Channel Modules
F-G1C8-LS
CGM Link System – 1 Group to 8 Channel Modules
2.1.1 Older Group-to-Channel Link Cables
Back when the channels were all 6 HP wide, there were
eight kinds of Link cables, connecting a group to 1, 2, 3, 4,
5, 6, 7, and 8 Cs respectively. The socket spacing was tai-
lored to 6 HP, so the introduction of the QSC made a
redesign necessary.
If you still have some older Link cables, you can use
them easily with newer products, even if some plugs will
inevitably end up being unused.
LINKING MASTERS AND GROUPS
There are two cases in which you may need to connect
groups and masters: to expand the functionalities of a sin-
gle group or to mix more groups. There are two Link Sys-
tem parts for this purpose: a strip and its extension, one
for each use.
By default, the Masterone ships with a master-to-group ca-
ble, allowing you to link a group to it. The master-to-group
cable has three IDC connectors: one for the master, one

Rev. 7 – Aug 2021 Page 16 of 107
for the group, and one for extending the connection to
other groups.
To connect more than one group, you need the group-
to-group extension. This cable has two IDC sockets and
one IDC plug. Connect the plug to the third MG socket,
and you’ll be able to link two more groups to a master.
The group-to-group sockets are spaced to accepts group
configurations of roughly 72 HP, allowing up to 4 QSCs.
It is possible to chain more GG extensions to one an-
other, such as to add a fourth group or connect groups
with larger channel configurations (up to eight QSCs).
The master-to-group cable ships with the Masterone and
cannot be purchased separately. The group-to-group exten-
sion is sold separately with the following code:
F-G2GX-LS
CGM Link System – Group to Group Extension
2.2.1 Older Master-to-Group Link Cables
The previous way of connecting groups and masters,
part of the Link Cables, consisted of four configurations
that allowed you to connect a master to 1, 2, 3, or 4
groups respectively.
The sockets’ spacing could fit up to 8 mono channels
per each new group.
The M module used to ship with a link cable to one
group, and the G module with link cables to four chan-
nels.
Anyway, both the older Link Cables and the new Link
System follow the same logic and are completely swappa-
ble. If you have older cables, feel free to use them with
the new CGM modules, and with the new Extension, if
you follow the connection rules.
If you accidentally connect more than one Channel to the
PSU, fear not: it’s not going to damage your system! It’s just
useless and may not be optimal for ground.
It is imperative not to swap connectors! Frap Tools may not
be held responsible in any way for problems or damage to
persons or property or to the device itself if the device is not
connected as indicated above.
3CHANNEL
The C module is the first member of the channel family.
Its concept draws from the monophonic channel strip of
a classic mixing console, with the crucial implementation
of CV controls over every key parameter, which makes it
fully suitable for the Eurorack environment.
The signal routing is designed to provide the best audio
quality and can be broken down to five color-coded main
parts: VCA (red), two effect sends (yellow and green), pan
(pink), and fader (white).
AMPLITUDE CONTROLS AND DIRECT OUTPUT
EFFECT SENDS
The two Send Level knobs (B.1) define the amplitude of
the channel signal to be routed to the group’s effect sends
mono outputs (B.4).
Just like the Main VCA, they can be voltage controlled
by patching unipolar CVs (either 0÷5 V or 0÷10 V) to its
CV input (B.2). This input allows you to automate the
effects of each channel individually in a way that it is not
possible on standard mixing consoles.
Both the effect sends are equipped with a Pre/Post Fader
switch (B.3), which improves the module’s usability. If set
post-fader (lower position, white dot), signal sent to the
external effects will be limited by the channel fader posi-
tion (A.11). This option is useful when you want your
dry/wet signal ratio always the same when you adjust a
channel’s volume.
If set pre-fader, the effect send will be defined by the
knob or the CV only, thus being completely independent
from the overall channel level. In this way, you can
achieve some effect such as lowering the channel fader
and leaving just the processed signal in the mix.
Another way of looking at the pre/post effect send is
that the former is an absolute level, while de second one
is relative (to the main fader, in this case).
PAN
The Pan control lets you distribute the processed signal
across the stereo image through the Pan knob (A.8).
This parameter is provided with a CV input (A.9),
which accepts both positive and negative signals (range
−5 V÷5 V).
The more the positive CV increases, the more the signal
is distributed to the right, and vice versa for negative CVs
and the left channel.
Given that the Pan is a bipolar control, the CV input
works slightly differently from the VCA and the Effect
Sends. In this case, when a CV is patched to its input, the
knob shifts the incoming CV towards the positive (right)
or negative (left) side. In other words, it acts as an offset,
not an attenuator.
CREATIVE FUNCTIONS
Every channel has three creative controls: the Mute but-
ton (C.1), the Solo in Place (C.2), and the Stereo PFL (Pre-
Fader Listening, C.4).
3.4.1 Mute
The Mute button (C.1) closes the main VCA. It equals
turning the VCA Level knob (A.5) all the way to zero. For
this reason, muting a channel allows you to mute all of its
outputs, including the effect sends.

Rev. 7 – Aug 2021 Page 17 of 107
3.4.2 Solo in Place
The Solo in Place button (C.2) selects the channels to keep
active when the group is in Safe Solo mode (C.3, see below
§5.4.2).
3.4.3 PFL
The Stereo PFL button (C.4) selects the channels sent to
the PFL circuit on the Master module (C.5, see below
§5.4.3).
4QUAD STEREO CHANNEL
The Quad Stereo Channel (QSC) consists of four stereo
channels, whit a design based on the Channel (§3) module
that, however, also borrows some concepts from the G
(§0) and the M (§6) modules. The color scheme reflects
the same routing of the modules: VCA (red), two effect
sends (yellow and green), pan (pink), auxiliary input (pur-
ple), and main faders (white).
The local sum outputs allow you to use the QSC also as
a standalone stereo mixer with mono effect sends. The
panning section can switch its behavior between stereo
source panning and mono sources crossfading.
AMPLITUDE CONTROLS AND DIRECT OUTPUT
The main VCAs defines the input gain of the signal
patched to the channel inputs (A.2, A.3) through the Level
knob (A.5). The Channel Faders (A.11) set the volume of the
audio signal to be sent to the Group module. Just like in
the Channel module, the VCA controls the amplitude of
the signal coming in, and the fader controls the amplitude
of the signal going out.
These two controls together, just like in classic mixing
consoles, allow you to define not only the amplitude of
the signal in the mix but also its “color.”
The input VCA goes ~6dB above unity gain, which
means that it can add a very smooth saturation to the in-
coming sound, which is often translated to adjectives such
as “fatter, punchier, warmer,” and so on.
Furthermore, such input level can be voltage-controlled
through the VCA Level CV Input (A.6), which accepts uni-
polar signals whose range can be either 0÷5V or
0÷10 V. When a signal is patched to this input, the Level
knob (A.5) becomes its attenuator.
Practice the VCA Level CV Input with this
Technique:
Sidechain #1
One of the differences between the QSC and the C is
that it features a local stereo output (A.12, A.13) instead
of individual Direct outputs (A.4). This allows you to use
the QSC as a stand-alone, four-channel stereo mixer.
4.1.1 Mono Auxiliary Input
The QSC also features an additional monophonic DC-
coupled input (A.21). This is an audio input with no con-
trols over the signal’s amplitude, and its signal routing is
very straightforward, adding the sound as is to the overall
sum routed to the Group or the two local outputs (A.13,
A.14).
The Mono Auxiliary input can be useful if you need a
spare mono channel for an external source that does not
need further amplitude processing.
PAN AND CROSSFADE
The Pan/Crossfade knob can perform two different tasks
according to the Pan/Crossfade switch position.
4.2.1 Pan
When the Pan/Crossfade switch (A.10) is set to the
lower position, the knob (A.8) acts as a stereo panorama
control, defining the balance of the (mono or stereo) au-
dio input across the left and right channels.
Two CV inputs (A.9) allow for external control of the
leftmost and rightmost channels’ Pan with positive and
negative voltages (range −5 V÷5 V). The more the posi-
tive CV increases, the more the signal is distributed to
right, and vice versa for negative CVs and the left chan-
nel.
Given that the Pan is a bipolar control, the CV input
works slightly different than the ones of the VCA and the
Effect Sends. In this case, when a CV is patched to its
input, the knob shifts the incoming CV towards the posi-
tive (right) or negative (left) side. In other words, it acts as
an offset, not an attenuator.
4.2.2 Crossfade
When the Pan/Crossfade switch (A.10) is set to the
higher position, the knob works as a “dual mono” cross-
fade that blends the signals patched to the two inputs and
outputs the same result across the left and right channel.
It can be useful, for example, for blending the sound of
two waveform outputs of the BRENSO oscillator (see p.
87) for a punchier, mono bassline or to mix two elements
of a drum pattern that do not need to be panned across
the stereo image.
Setting all the stereo channels to the Crossfade can even
let you use the QSC as an almost-eight-channel-mono
mixer.
CREATIVE FUNCTIONS
Every channel has three creative controls: the Mute but-
ton (C.1), the Solo in Place (C.2), and the Stereo PFL (Pre-
Fader Listening, C.4).

Rev. 7 – Aug 2021 Page 18 of 107
4.3.1 Mute
The Mute button (C.1) closes the main VCA. It equals
turning the VCA Level knob (A.5) all the way to zero. For
this reason, muting a channel allows you to mute all of its
outputs, including the effect sends.
4.3.2 Solo in Place
The Solo in Place button (C.2) selects the channels to keep
active when the group is in Safe Solo mode (C.3, see below
§5.4.2).
4.3.3 PFL
The Stereo PFL button (C.4) selects the channels sent to
the PFL circuit on the Master module (C.5, see below
§5.4.3).
5GROUP
The Group is a stereo module that blends the signals
coming from the channels linked to it (up to eight) and
takes care of their signal routing.
The group “puts into practice” all the information de-
fined by the channel’s controls: volume, effect send vol-
ume, stereo panning.
It consists of three sections: the amplitude controls
(white), and the two effect sends and returns (yellow and
green).
As of today, the Group is the only module that does not
require power, as a Channel powers it through its IDC
cable.
AMPLITUDE CONTROL
The main control is the Group Fader (A.16), which sets
the Group’s final volume. This is the overall amplitude of
the sum of the connected channels and the returns.
It features a pair of peak LEDs on the top left and right
of the knob that notifies when the left or right Channel
(respectively) are clipping.
EFFECT SENDS/RETURNS
This section of the module is the CGM interface for ex-
ternal signal processing. It consists of two specular sec-
tions, marked yellow and green, each of which features a
mono output (Send) and a stereo input (Return).
5.2.1 Sends
The Send jack socket (B.4) outputs a mono signal, which
is the sum of all the signals processed for that send by each
Channel connected to the Group.
5.2.2 Returns
The Return section is divided into two specular columns,
the left one for the yellow return, the right one for the
green return.
The first two rows from the top are the Return inputs
(B.5, B.6). They are semi-normalled, meaning that they
can work either in stereo (when two cables are plugged)
or in dual mono (when only one cable is plugged into any
of the two inputs). When using two cables for stereo re-
turn, the top jack carries the left signal and the bottom
jack the right one.
As soon as an audio signal is connected, it is routed to
the stereo return: each Return section is equipped with its
own stereo VCA, which is identical to the ones used in
the red, yellow, and green sections of the Channel module.
To control the amplitude of the effect return, use the Re-
turn Level knob (B.7).
The return level can be externally controlled through
the CV inputs (B.8), which accept signals with a range of
0÷5 V or 0÷10 V, allowing any creative use of the stereo
effect returns. When a CV is patched to any of these in-
puts, then the Level pot (B.7) acts as an attenuator.
Practice the Send/Return modulation with
this Technique:
Sidechain #1
GROUP OUTPUT
Every group has two Group Outputs that are stereo paired
(A.14, A.15). They can be configured to output just the
sum of the processed signals (from the stereo returns) or
the overall sum of the channels and effects.
5.3.1 Group Jumpers Configurations
The Group L/R outputs (A.14, A.15) can be configured
in two ways through the jumpers on the back of the PCB.
In the first mode, they output just the sum of the two
effect returns: this mode is especially useful for further
processing of the effects.
In the second mode, they output the same signal that is
routed to the Master module: a sum of all the channels,
plus the yellow and green effect return. This mode is es-
pecially useful for smaller setups, where a Master module
is not needed because it allows you to use the Group mod-
ule as your final mixing unit.
To set the modules to the first mode, place the two
jumpers on the back of the PCB to pins 1 and 2 from the
left (Figure 10).
To set the modules to the second mode, place the two
jumpers on the back of the PCB to pins 2 and 3 from the
left (Figure 11).
The signal routed to the Master module via IDC cable
will not be affected by any of these jumper configurations.

Rev. 7 – Aug 2021 Page 19 of 107
Figure 10: Pins 1 and 2.
Figure 11: Pins 2 and 3.
It is imperative not to connect the jumpers to any other con-
nector except the two mentioned in this section and shown
in the pictures below. Frap Tools may not be held responsible
in any way for problems or damage to persons or property or
to the device itself if the device is not connected as indicated
above.
CREATIVE FUNCTIONS
Every Group has three creative controls: the Group Mute
button (C.1), for all the connected Channels and send/re-
turn signals; the Safe Solo switch (C.3), which enables the
Solo In Place function on each of the connected Channels
when moved to the left, and the Stereo PFL (C.4), accessi-
ble via the Master module for all the connected Channels
and Send/Return signals.
5.4.1 Group Mute
The Group Mute button (C.1) shuts the whole group,
including the effect sends and returns. It equals turning
the Group Fader (A.16) all the way to zero.
Please note that the group outputs won’t be affected by
the mute button: to take advantage of the Group Mute
function, the group needs to be routed to a master mod-
ule, and the audio taken from this last one.
5.4.2 Safe Solo
The Safe Solo function allows the musician to isolate cer-
tain channels in the mix, thus muting all the remaining
ones. It is achieved through two operations: pushing the
Solo in Place button on the Channel module and moving the
Safe Solo switch on the Group module: the Solo in Place
button will determine which channels will be soloed
(which will be marked with the white LED) and which
ones muted; the Safe Solo switch will put this selection into
practice (and the group too will display a white LED). It
is called Safe Solo because it safely allows you to select the
channels you want to solo in advance, without affecting
the ongoing performance.
5.4.3 PFL
The Stereo PFL button (C.4) allows you to prelisten the
group when it is muted or when its fader is set to the
lowest position. To take advantage of this function, you
need to connect the group to the Master module with its
PFL Blend (C.5, see below §).
6MASTER (DISCONTINUED)
The Master module is the last step in a CGM setup, and
its main purpose is delivering the audio of the Eurorack
system to the outside world.
It consists of three sections: the amplitude control
(white), the Headphones/PFL section (blue), and the
Auxiliary input (purple).
AMPLITUDE CONTROL
The main control is the Master Fader (A.19), which sets
the volume of the sound at the Master’s left and right out-
puts (A.17, A.18). This is the overall amplitude of the sum
of the connected group, which, at this stage, can gain an
additional 6dB.
The Master features two columns of five LEDs each
(three green, one yellow, and one red) that act as a visual
monitor of the audio levels on the left and right channel,
respectively. It acts a LED VU-meter, with the LED val-
ues being, from bottom to top: -6dBu, −1dBu, +4dBu,
+7dBu, +10dBu.
AUXILIARY STEREO INPUT
The Master module’s purple section features a stereo
3.5 mm jack input (A.20) with a dedicated amplitude con-
trol knob (A.22). Patching any audio source to this input
will add it to the main mix.
The Auxiliary Input features a PFL button (C.4) just like
the Channels and the Groups which allows you to moni-
tor the sound before blending it to the mix.
CREATIVE FUNCTIONS
The Master module features a Headphones section that is
designed for two purposes: 1) monitoring the mix through
a pair of headphones, with independent level, and 2) lis-
tening to individual channels without them being mixed,
through the Pre-Fader Listening controls.
6.3.1 Headphones
The headphones must be connected to the stereo
3.5 mm jack output (A.23). The bottom potentiometer
(A.24) sets the volume of the headphones, and the top one
(C.5) blends the main out signal (white) with the PFL sig-
nal (blue).
6.3.2 PFL
PFL (PreFader Listening) allows the musician to send to the
Headphones output any channel, group or the Aux input

Rev. 7 – Aug 2021 Page 20 of 107
when their main fader is at 0, in order, for instance, to
preview it before it is mixed.
PFL is achieved through two operations: pushing the
PFL button (C.4) on the Channel or Group modules or
on the Aux input (the blue LED will light up) and adjust-
ing the PFL level through the PFL Blend knob (C.5).
PFL previews the Channel’s sound before the main
fader: this means that its amplitude will be determined by
the Red VCA level, which means that the green and yel-
low Sends cannot be PFL’d from the Channel.
This is when the Group PFL comes in handy: in order
to pre-listen the effect sends and returns before sending
them in the mix, you can mute the Group’s and activate
its PFL button: from now on, everything that is managed
by the Group will be safely pre-listened without affecting
the main mix, including individual Channels’ Main
Fader settings, sends and returns.
Please note that Safe Solo overrides PFL: this means that
you can perform Safe Solo when a Group is in PFL, but
you cannot PFL a channel whose Solo in Place button is
off when its Group is in Safe Solo mode: the reason is that,
as explained above, the Safe Solo works as a “Mute region,”
i.e., muting all the unselected channel’s red VCAs.
7MASTERONE
The Masterone replaced the Master module as the
gateway from the modular system to the outside world.
Following and expanding the Master concept, we de-
signed it with the sole purpose of providing high-quality
outputs in as many formats as possible. For this reason,
since it is not meant to be connected to any other Euro-
rack module, it is the only Frap module that does not
have any 3.5 mm jack connection (as of today).
It consists of two sections: the amplitude control (white),
and the Headphones/PFL section (blue). An additional
mono output (light green) is part of the amplitude section.
Two arrays of 12 LEDs each act as a stereo VU meter:
they measure the amplitude increments from –40 to
15 dBu, with peak memory.
AMPLITUDE CONTROL
The main control is the Master Fader (A.19), which sets
the overall amplitude of the sounds coming from the con-
nected groups. At this stage, it can add an additional 6 dB
of gain: it is thus possible to saturate the circuit to intro-
duce distortion and nonlinearities in the sound.
The Master features two columns of 12 LEDs each that
act as graphical VU-meter of the audio levels on the left
and right channel, respectively.
6
See the Core Concepts chapter, section 7, p. 10.
The Masterone has three kinds of outputs: pseudo-bal-
anced stereo TRS, balanced stereo XLR, and pseudo-
balanced mono.
7.1.1 Pseudo-balanced TRS Outputs
These ¼" jack outputs (A.17, A.18) are technically
identical to ones on the Master module. They output an
unbalanced (or pseudo-balanced, see below) stereo signal
(left and right channels, respectively).
The line signal is at Eurorack level
6
, so, in case it is too
hot for some destinations, it is possible to attenuate it
through the Line/Inst switch (A.25). Once the switch is
set to the lower position, the output is attenuated by
~15dB.
Just like the Master outputs, these outputs are pseudo-
balanced. If you use a standard ¼" mono jack, you’ll ob-
tain an unbalanced output. If you patch a ¼" TRS jack,
you can connect them to a balanced system with better
performance since the ring and the sleeve are both con-
nected to ground. However, the best option for balanced
systems is to use the balanced outputs (see below).
7.1.2 Balanced XLR Outputs
These XLR outputs (A.26, A.27) provide a balanced
line signal that mirrors the one routed to the TRS out-
puts. However, due to the nature of the balanced systems,
their output will sound twice as louder as the pseudo-bal-
anced one (+6 dB).
Even in this case, if the signal is too hot, it is possible to
scale it down. Once the Line/Mic switch (A.28) is set to
the lower position, the signal will be attenuated by 30 dB.
7.1.3 Mono Out
The bottom output (A.29) provides an additional,
pseudo-balanced monophonic output with an attenuator.
It outputs the sum of the left and right channels. It can
be used for live monitoring, or for for more creative uses,
such as patching it to a specific amplifier for parallel pro-
cessing in a studio environment.
An amplifying circuit provides an additional 6 dB of
gain and 15 dB of attenuation calculated from the refer-
ence 0, the Line level of the pseudo-balanced stereo out-
puts. Rotate the mono out fader (A.30) to the left to at-
tenuate the signal and to the right to amplify it.
CREATIVE FUNCTIONS
The Masterone features a Headphones section designed
for two purposes: 1) monitoring the mix through a pair of
headphones, with independent level, and 2) listening to
individual channels without them being mixed through
the Pre-Fader Listening controls.