Yamaha Audio GC2020C User Manual

COMPRESSOR/LIMITER

GC2020C

Owner’s Manual
Mode d’emploi
Bedienungsanleitung
Manual del propietario

GAIN

REDUCTION

EXP GATE THRESHOLD RATIO ATTACK RELEASE INPUT OUTPUT

GC2020C

COMP/LIMITER

COMP

0
–4
–8

–16

0 10 0 10 0 10 0 10

–24

48

35

0.3 0.5

20

2

1

10

1

0.1

00

20

0.2

0.05

CHANNEL A CHANNEL B

secms

SIGNAL PEAK

1

2

LINK COMP

GAIN

REDUCTION

EXP GATE THRESHOLD RATIO ATTACK RELEASE INPUT OUTPUT

0
–4
–8

–16

0 10 0 10 0 10 0 10

–24

48

2

1

35

20

10

1

0.1

00

20

0.2

0.05

0.3 0.5

secms

SIGNAL PEAK

1

2

POWER

ON OFF

i

Welcome to the GC2020C Compressor/Limiter

Introduction

Thank you for choosing the Yamaha GC2020C Compres­sor/Limiter. The GC2020C is a 2-channel high-performance
compressor/limiter designed for professional recording and
sound reinforcement applications. The GC2020C provides a
wide variety of control features for precise tailoring of com­pression and limiting parameters. It also features an
expander gate to eliminate source noise that can be accentu­ated by the compression process.

GC2020C compression can be used to add extra punch and
a more consistent level to a final mix, and channels can be
linked for stereo operation. A small amount of compression
provides a more consistent signal level when recording a
singer that tends to move closer to or further away from a
vocal microphone. Essentially, the compressor is reducing

English

the dynamic range. This technique can also be used with
other instruments, such as acoustic guitar, bass guitar, and
piano. In fact, any instrument with a wide dynamic range can
be recorded more easily with a little compression applied.
Creative compressor application include adding extra punch
to bass, snare, and tom tom drums. GC2020C limiting can
be used to protect speakers in a sound reinforcement system.

Whether your applications are signal control, signal correc­tion, or simply creative—the GC2020C is flexible enough to
handle all your needs.

To get the best from your GC2020C, read this manual thor­oughly, and keep it in a safe place for future reference.

Table of Contents

What’s a Compressor/Limiter? . . . . . . . . 1

Compressor/Limiter Functions . . . . . . 1

Compressor/Limiter Parameters . . . . . 2

Setting Up the Compressor/Limiter . . . 4

What’s an Expander/Gate? . . . . . . . . . . . 5

Setting Up the Expander/Gate . . . . . . 5

Controls & Connections . . . . . . . . . . . . . 6

Front Panel . . . . . . . . . . . . . . . . . . . . . 6

Rear Panel . . . . . . . . . . . . . . . . . . . . . . 7

Specifications . . . . . . . . . . . . . . . . . . . 8

Dimensions . . . . . . . . . . . . . . . . . . . . . 9

Block Diagram . . . . . . . . . . . . . . . . . 10

IMPORTANT NOTICE FOR

THE UNITED KINGDOM

Connecting the Plug and Cord

IMPORTANT: The wires in this mains lead are coloured in accordance
with the following code:
BLUE : NEUTRAL
BROWN : LIVE
As the colours of the wires in the mains lead of this apparatus may not
correspond with the coloured markings identifying the terminals in your
plug proceed as follows:

The wire which is coloured BLUE must be connected to the terminal
which is marked with the letter N or coloured BLACK.

The wire which is coloured BROWN must be connected to the terminal
which is marked with the letter L or coloured RED.

Making sure that neither core is connected to the earth terminal of the
three pin plug.

* This applies only to products distributed by YAMAHA - KEMBLE

MUSIC (U.K.) LTD.

GC2020C Compressor/Limiter Owner’s Manual

ii

Precautions

Avoid excessive heat, humidity, dust,
and vibration

Keep the unit away from locations where it is likely to be
exposed to high temperatures or humidity—such as near
radiators, stoves, in direct sunlight, etc. Avoid locations that
are subject to excessive dust accumulation. Extreme vibra­tions can cause mechanical damage.

Avoid physical shocks

Strong physical shocks can damage the unit. Handle it with
care.

Install the unit with plenty of space for ventilation
This unit should be installed in such a way as to maintain a

gap of 10 cm or more between the rear of the unit and the
wall. This will prevent heat build-up inside the unit and pos­sible fire hazard.

Do not open the unit, or attempt
repairs or modifications yourself

Always use the correct power source

Make sure the power source voltage specified on the rear
panel matches your local AC mains supply:

US & Canadian Model: 120V AC, 60 Hz
General Model: 230V AC, 50 Hz
UK Model: 240V AC, 50 Hz

This product contains no user-serviceable parts. Prefer all
maintenance to qualified Yamaha service personnel. Open­ing the unit and/or tampering with the internal circuitry will
void the warranty.

Make sure the power is off before
making or removing connections

Always turn the power OFF prior to connecting or discon­necting cables. This is important to prevent damage to the
unit itself as well as other connected equipment.

Handle cables carefully

Always plug and unplug cables—including the AC cord—by
gripping the connector, not the cord.

Clean with a soft dry cloth

Never use solvents such as benzine or thinner to clean the
unit. Wipe it clean with a soft, dry cloth.

GC2020C Compressor/Limiter Owner’s Manual

What’s a Compressor/Limiter?

What’s a Compressor/Limiter?

This section explains the main functions of the Compressor/Limiter. Its parameters, setup procedure, and the expander/gate.

Compressor/Limiter Functions

Compressor

Generally, a compressor is used to fit a large signal into a
small space. Specifically, in a situation where the dynamic
range of the original audio signal is larger than the electronic
reproduction equipment that is to process it can handle, a
compressor can reduce the dynamic range of the signal to fit
neatly within the limits of the recording or reproduction
equipment. Of course, this must be done without adding
distortion to the signal itself.

Compression is expressed in terms of a ratio—the compres­sion ratio. This ratio describes how much the signal appear­ing at the output of the compressor changes in relation to a
given change in the level of the original signal applied to the
input. If no compression is applied and the input signal
doubles in level, then the output signal will also double in
level, precisely following the change in the input signal. This
corresponds to a compression ratio of 1:1 (read “one to
one”) —a change of 1 at the input produces a change of 1 at
the output—i.e. no compression. Now if we apply some
compression, a smaller change in the level of the output sig­nal will be observed for the same change in input signal
level. A compression ratio of 2:1, for example, would mean
that the level of the output signal will change only half as
much as the input signal. Expressed in decibels, a compres­sion ratio of 20:1 would mean that a 20 dB change in the
level of the input signal would result in only a 1 dB change in
the level of the output signal. Thus, a compressor is able to
reduce the dynamic range of an audio signal by any desired
amount. See Figure 1.

(dB)

Output Signal Level

0

Input Signal Level

COMPRESSION

1:1 NO COMPRESSION

2:1 COMPRESSION

Threshold
Level

(dB)

Limiter

Limiting is basically extreme compression that is set to affect
only signals above a certain level. This is particularly useful
for limiting only peaks that exceed the handling capacity of
the related equipment, without affecting the rest of the sig­nal. See Figure 2.

(dB)

Limiting
Threshold

Output Signal Level

0

Input Signal Level

LIMITING

Figure 2

Suppose we wanted to limit the peak levels in a program to
a maximum of 0 dBm, in order to prevent saturation and
distortion in a tape recorder. First we would set the “thresh­old” level to 0 dB—the threshold level is the input signal
level at which the limiter will begin to operate. Then we
would set the maximum (or near maximum) compression
available—

∞

:1 (infinity compression). Infinity compres­sion means that absolutely no change in the output level will
occur no matter how much the input signal changes. As a
result, all signal content below the threshold level (0 dB) will
be passed exactly as it appears at the limiters input. Signals
exceeding the threshold level, however, will be output at the
threshold level and will rise no higher. In this case no signal
exceeding 0 dB will appear at the limiter’s output. The actual
audio signal remains untouched, just its average (r.m.s.)
level is kept within the defined limits.

(dB)

1

English

Figure 1

GC2020C Compressor/Limiter Owner’s Manual

Compressor/Limiter Parameters

2

Compressor/Limiter Parameters

Threshold Level

Threshold is the signal level at which compression or limit­ing begins. All signals below the set threshold level are
passed as received at the INPUT jacks, with no compression
or limiting applied. Signals going above the set threshold
level, however, are compressed or limited according to the
settings of the RATIO, ATTACK, and RELEASE controls.

Ratio

This is the amount of compression applied to signals that
exceed the threshold level set by the THRESHOLD control.
The compression ratio is expressed in terms of the amount
of change in the level of the input signal in relation to the
corresponding amount of change in the level of the output
signal. A high ratio means a lot of compression. A compres­sion ratio of 1:1, therefore, implies no compression—a
change of 1 in the level of the input signal produces a corre­sponding change of 1 in the level of the output signal. A
compression ratio of 2:1, however, means that for a given
change in the level of the input signal (2) the level of the out­put signal will only change half as much (1). The extreme
would be a compression ratio of
ing that no matter how much the input signal level changes
the output signal level will remain constant. The
pression ratio is most commonly used in hard limiting
applications where the signal level must be prevented from
exceeding a specific value (frequently 0 dB). Extremely high
compression ratios in the range of 20:1 can add sustain to
instrument sounds—especially electric guitar and bass—as
well as creating a contemporary drum sound. Lower com­pression ratios—from less than 2:1 to 8:1—are useful for
making vocals sound smoother and minimizing the level
variations that occur when a speaker or singer moves closer
to or further away from a microphone.

∞

:1 (infinity to one), mean-

∞

:1 com-

Attack Time

The Attack Time determines how long it takes—in millisec­onds—before the full amount of compression is applied
once the threshold level is exceeded. The ATTACK time
range is from 0.2 milliseconds, a very fast attack, to a rela­tively slow 20 milliseconds.

The attack time setting depends largely on the type of signal
being processed and the type of effect desired. A very fast
attack, for example, will compress the initial attack of an
instrumental note making it sound “dull”. High levels of
compression are sometimes used on electric guitar, for
example, to give the sound greater sustain. In this applica­tion it is often better to set a longer attack time so that the
crisp attack of the guitar note “gets through” before full
compression is applied. Set the attack time to accommodate
the natural attack of the sound being processed.

ATTACK TIME Control Function

Attack Time set to zero

Input Signal

Fast Attack Time

Attack Time

+30

+20

+10

Threshold level

0

–10

–20

–30

Output Signal Level (dB)

–40

–50

–60–70 [phone] +10 +20

Intput Signal Level (dB)

COMPRESSION RATIOS

1:1

2:1

4:1

8:1
:1

Figure 3

GC2020C Compressor/Limiter Owner’s Manual

Slow Attack Time

20:1

Attack Time

Figure 4

Release Time

The Release Time determines how long it takes for the com­pression to return to zero once the audio signal falls below
the threshold level. The RELEASE time range is from 50 mil­liseconds (0.05 seconds) to 2 seconds. Like the ATTACK
control, the RELEASE control setting depends on the type
of signal being processed and the desired effect.

RELEASE TIME Contorl Function

Release Time set to zero

Input Signal

Fast Release Time

Release Time

Compressor/Limiter Parameters

• The compressor/limiters use the Threshold Level setting

of the channel whose level setting is higher.

• The expander/noise gates use the Threshold Level setting

of the channel whose level setting is lower.

• For Attack Time and Release Time, the channel with the

faster (shorter) settings determines the settings.

External trigger

Compressor/limiters normally begin compression when
they detect that the input signal has exceeded the threshold
level. However, it is also possible to use a signal other than
the input signal as the trigger. The GC2020C provides a
SIDE CHAIN OUT jack that splits the input signal and
sends it to an external device, and a SIDE CHAIN IN jack
that lets a signal from an external device control the com­pressor/limiter. Using an external trigger allows more
sophisticated control of the GC2020C.

For example, if you connect the SIDE CHAIN OUT jack of
channel B to the SIDE CHAIN IN jack of channel A so that
channel A is controlled by an external trigger (i.e. channel
B), you can apply the compressor/limiter to the channel A
signal only when the channel B signal exceeds the threshold.
This is an easy way to produce the “ducking” effect that DJ's
or announcers use to automatically lower the volume of the
music when they speak.

3

English

Slow Release Time

Release Time

Figure 5

The main reason for this control is that if compression
stopped abruptly the instant the signal fell below threshold
level there would be a corresponding abrupt and unnatural
change in the level of the audio signal—particularly with
musical instruments that have a long, gentle decay slope.
Unless a particular effect is desired, set the RELEASE time to
accommodate the signal being processed.

Link

This function makes the compressor/limiter of channel A
and of channel B operate together. When a compressor/lim­iter is used to process a stereo signal, using two independent
channels of compression causes the stereo image to waver
unsteadily, producing an unnatural effect. If the two chan­nels are linked, however, the same compression is applied to
both channels, preserving the stereo image. When Link is
ON, the parameters of both channels are linked as follows.

INT EXT

CHANNEL A

INPUT

SIDECHAIN SIDECHAIN

IN

KEY

INT EXT

OUT

OUTPUT

+4dB

+4dB

KEY

INT EXT

IN

OUT

By connecting an equalizer between the SIDE CHAIN OUT
and SIDE CHAIN IN jacks, boosting the 3–5 kHz region,
and setting that channel to operate with an external trigger,
you can apply a de-esser effect, in which the compres­sor/limiter applies only to sibilant sounds (sounds with a
pronounced S component).

INT EXT

CHANNEL A

INPUT

OUTPUT

+4dB

+4dB

KEY

INT EXT

SIDECHAIN

IN

OUT

Equalizer

GC2020C Compressor/Limiter Owner’s Manual

Setting Up the Compressor/Limiter

4

Setting Up the Compressor/Limiter

1. Set the INPUT and OUTPUT controls midway.

2. Set the Threshold Level and Ratio as appropriate for
your application.

3. Adjust the OUTPUT control so that the PEAK indicator
just lights up at the loudest signals.

4. Set the Attack and Release times as appropriate.

GC2020C Compressor/Limiter Owner’s Manual

What’s an Expander/Gate?

The GC2020C features a expander/gate that is independent
of the compressor/limiter. Expander/gate is a function that
effectively eliminates hum or noise that would otherwise be
heard during silent portions of the program. It works by
closing the gate to cut off the output signal when the input
signal falls below a specified level (the gate threshold level).

• EXP GATE Function

INPUT SIGNAL

Music Signal

Level

Noise

Normally you will set the gate level below the lowest level of
the musical portion, so that the gate will always be “open”
during the music to let the signal pass. Hum or noise that is
lower in level than the music will thus be effectively elimi­nated.

OUTPUT SIGNAL

Level

What’s an Expander/Gate?

Music Signal

Noise

Expander gate
threshold level

5

English

Time

Setting Up the Expander/Gate

1. Adjust the input level so that the PEAK indicator just
lights up at the loudest signals.

2. Without playing the instrument, gradually raise the Gate
Threshold Level, and set it at a position slightly above the
point where noise is no longer audible.

3. Input a signal and check that its decay is not cut off
unnaturally for the most softly played notes. If the tail
end of the decay is cut off, lower the Gate Threshold
slightly.

Signals in
this range
muted

Signals in
this range
muted

Time

Signals in
this range
muted

GC2020C Compressor/Limiter Owner’s Manual

Controls & Connections

6

Controls & Connections

Front Panel

BA

GAIN

REDUCTION

COMP

1

POWER Switch

EXP GATE THRESHOLD RATIO ATTACK RELEASE INPUT OUTPUT

0
–4
–8
–16

0 10 0 10 0 10 0 10

–24

48

35

20

2

1

00

1

20

0.2

CHANNEL A CHANNEL B

SIGNAL PEAK

0.3 0.5

10

1

0.1

2

0.05
secms

Press this switch to power up the GC2020C. The power indi­cator lights up. To power down the GC2020C, press this
switch again. The power indicator goes out.

2

LINK switch

This turns Link ON and OFF. When Link is ON, the LED
indicator lights up. Press the switch once again to turn it
OFF. When Link is ON, compression and limiting is applied
equally to both channels, so that a stereo signal can be pro­cessed correctly.

NOTE: When using Link, set the COMP switch on both
channels to ON. And set the INPUT control and COMP
RATIO control on both channels to the same values.

3

COMP switch & indicator

This switch determines whether the compressor/limiter is
active, or bypassed. When this switch is ON, the LED indi­cator lights up, and the compressor/limiter circuit is active.
When it is OFF, the indicator is OFF, and the compres­sor/limiter circuit is completely bypassed, so the input signal
is sent straight to the output jack.

4

GAIN REDUCTION meter

This five-segment LED meter shows the amount of gain
reduction that is being applied by the compressor/limiter.
The LEDs indicate 0 dB, –4 dB, –8 dB, –16 dB, and –24 dB of
gain reduction.

5

EXP GATE control & indicator

The EXP GATE control is used to set the threshold level of
the expander gate. When this control is turned hard left, the
gate function is OFF. The LED above the EXP GATE control
shows the operation of the expander gate, and light up when
the gate is closed.

SIGNAL PEAK

0.3 0.5

10

1

0.1

2

0.05
secms

LINK COMP

GAIN

REDUCTION

EXP GATE THRESHOLD RATIO ATTACK RELEASE INPUT OUTPUT

0
–4
–8

–16

0 10 0 10 0 10 0 10

–24

6

THRESHOLD control

48

2

1

35

20

1

20

00

0.2

This sets the level at which the compressor/limiter begins to
take effect.

RATIO control

7

This determines the amount of compression that is applied
to signals that exceed the threshold level. The range is from 1
(1:1 ratio) to infinity (infinity:1 ratio).

ATTACK control

8

This determines the speed (in milliseconds) with which
compression begins after a signal exceeding the threshold is
detected. The range is from 0.2 msec (very fast attack time)
to 20 msec (relatively slow attack).

9

RELEASE control

This determines the speed at which compression is removed
after the signal falls below the threshold level. The range
from 50 msec to 2 sec.

INPUT control

0

This controls the input level. A wide range of input signals
can be accommodated.

SIGNAL indicator

A

This indicator shows that a signal is present in the compres­sor/limiter. It lights up when the output signal is 13 dB
below the nominal level.

B

PEAK indicator

This indicator shows that a signal is about to clip. It lights up
when the output signal is 3 dB below the clip point. Adjust
the OUTPUT control so that this indicator just lights up at
the loudest signals.

POWER

ON OFF

10C98765432

GC2020C Compressor/Limiter Owner’s Manual

C

OUTPUT control

This controls the output level. When the input signal is
compressed by the compressor/limiter, it may appear to
have diminished in volume. This knob adjusts the level of
the signal that has been processed by the compressor/lim­iter. While turning the COMP switch ON/OFF, adjust the
OUTPUT control so that the volume of the bypassed and
processed signals is the same.

Rear Panel

INPUT

OUTPUT

+4dB

+4dB

SIDECHAIN SIDECHAIN

IN

KEY

INT EXT

OUT

CHANNEL ACHANNEL B

OUTPUT

+4dB

INPUT

+4dB

KEY

INT EXT

Rear Panel

7

English

IN

OUT

DEFG

D

OUTPUT jacks

These are the output jacks. Three-pin XLR type connectors
(male) and 1/4" phone jacks are provided. Both types are
balanced. Nominal impedance is 600 ohms for both.

E

INPUT jacks

These are the input jacks. Three-pin XLR type connectors
(female) and 1/4" phone jacks are provided. Both types are
balanced. Nominal impedance is 600 ohms for both.

SIDE CHAIN INT/EXT switch

F

This switch selects the signal source for the circuit that
detects the point at which the compressor/limiter is applied.
With a setting of INT, the detector uses the channel signal.
With a setting of EXT, the detector uses the signal from the
SIDE CHAIN IN jack.

SIDE CHAIN IN/OUT jack

G

These jacks are used to split the input signal, or to use an
external signal as the trigger for the compressor/limiter.

GC2020C Compressor/Limiter Owner’s Manual

Specifications

8

Specifications

Frequency Response 0+1 dB 20 Hz— 20 kHz @+4 dB Link OFF/ON

Total Harmonic Distortion Less than 0.05% (THD + N)

Hum & Noise (Average,
Rs=600 Ω) (Measured with
BPF 20 Hz — 20 kHz)

Compression Ratio 1 : 1 —

Compressor/Limiter
Threshold Level

Expander Noise Gate
Threshold

Attack Time 0.2 ms — 20 ms

Release Time 50 ms — 2.0s

Gain Reduction 5 Segment LED Meter

Peak Indicators Red LED on each channel lights up when

Signal Indicators Green LED on each channel lights up

–3

Controls

20 Hz — 20 kHz @+4 dB

–85 dB Power

∞

: 1

(Maximum limiting 32 dB)

+20 dB — –35 dB
(Input Control at 0 : +20 dB — +5 dB)
(Input Control at 5 : +20 dB — –20 dB)
(Input Control at 10 : +5 dB — –35 dB)

+0 dB — –80 dB
(Input Control at 0 : 0 dB — –40 dB)
(Input Control at 5 : –25 dB — –65 dB)
(Input Control at 10 : –40 dB — –80 dB)

the output signal is 3 dB below clipping.

when the output signal is 17 dB below
the nominal level.

(per CH.)

Consumption

Power
Requirement

Dimensions
(W×H×D)

Weight 3.2kg

* Measurement conditions

Link switch............................ OFF

Input Level ............................ 5 (center)

Output Level .........................5 (center)

Exp. Gate.............................. switch OFF

Comp. Ratio.......................... 1 : 1 (minimum)

Threshold Level .....................0 (minimum)

Attack Time........................... 0.2 ms (minimum)

Release Time ......................... 50 ms (minimum)

Key switch............................. INT

Input Level, Output Level,
Exp. Gate (with ON/OFF switch),
Comp. Ratio, Threshold Level,
Attack Time, Release Time,
Comp switch

20W

USA and Canada
120 V 60 Hz
GENERAL
230 V 50 Hz

480×49.4×246mm

Input Characteristics

Connection

INPUT 15 kΩ 600 Ω Lines +4 dB (1.23 V) +4 dB (1.23 V) +20 dB (7.75 V)

Actual Load

Impedance

For Use With Nominal Sensitivity

Output Characteristics

Connection

OUTPUT 150 Ω 600 Ω Lines +4 dB (1.23 V) +20 dB (7.75 V)

Actual Source

Impedance

In these specifications, when dB represents a specific voltage, 0 dB is referenced to 0.775 Vrms.
XLR type connectors and phone jacks (TRS) are balanced. (T=HOT, R=COLD, S=GND)
Sensitivity is the level required to produce an output of +4 dB (1.23 V).

GC2020C Compressor/Limiter Owner’s Manual

For Use With

Nominal

Nominal

Input level

Nominal

Output Level

Maximum Before

Maximum Before

Clipping

Clipping

Connectors

XLR-3-31 Type

Phone Jack

Connectors

XLR-3-32 Type

Phone Jack

SIDE CHAIN Characteristics

Specifications 9

Connection

SIDE CHAIN IN 27 kΩ 600 Ω Lines +4 dB (1.23 V) +4 dB (1.23 V) +20 dB (7.75 V) phono

Connection Actual Source Impedance

SIDE CHAIN OUT 600 Ω 10 kΩ Lines +4 dB (1.23 V) +20 dB (7.75 V) phono

Actual Load

Impedance

For Use With

Nominal

Sensitivity

For Use With

Nominal

Nominal

Nominal

Input Level

Output Level

Maximum Before

Maximum Before

Clipping

Clipping

Connectors

Connectors

In these specifications, when dB represents a specific voltage, 0 dB is referenced to 0.775 Vrms.
Sensitivity is the level required to produce an output of +4 dB (1.23 V)

Dimensions

228

D:246

150

English

W:480

• Specifications subject to change without notice.

402

2

30

16

H:49.4

44

5.4

Unit : mm

GC2020C Compressor/Limiter Owner’s Manual

10 Block Diagram

Block Diagram

INPUT +4dB

CHANNEL A

SIDECHAIN

OUT

HA

INPUT OUTPUT

IN

THRESHOLD

INT

EXT

KEY

EXP GATE

EXP GATE

VCA

ENVELOPE

GENERATOR

RELEASEATTACK

f(x)=1/x

LINK

(to CH B)

(to CH B)

COMP

COMP

RATIO

RATIO

PEAKSIGNAL

VOLTAGE
SHIFTER

0

-4

-8

-16

-24

GAIN REDUCTION

EXP GATE

CHANNEL A

OUTPUT

+4dB

HA

INPUT +4dB

CHANNEL B

OUT

SIDECHAIN

IN

GC2020C Compressor/Limiter Owner’s Manual

VCA

CHANNEL B

COMP

OUTPUTINPUT

SIGNAL PEAK

OUTPUT

+4dB

i

COMPRESSOR/LIMITER

Français

GC2020C

Mode d’emploi

Bienvenue au Compresseur/Limiteur GC2020C

Avant-propos

Merci d’avoir porté votre choix sur un Compressor/Limiter
GC2020C de Yamaha. Le GC2020C est un compresseur/lim­iteur professionnel à deux canaux qui convient tant pour les
enregistrements audio que pour des tâches de sonorisation.
Le GC2020C vous propose un grand registre de fonctions de
contrôle, vous permettant ainsi de vous confectionner exact­ement le son requis au moyen des paramètres de compres­sion et de d’écrétage Doté d’une fonction expandeur/Gate, il
permet en outre d’éliminer du souffle et tout autre bruit de
fond qui risqueraient d’être amplifiés par le compres­seur/écrêteur.

La compression du GC2020C peut être utilisée pour conférer
plus de “punch” au mix final, voire pour éviter de trop
importantes différences de niveau. Un soupçon de compres­sion rendra le chant plus égal, car nous savons tous qu’un
chanteur a tendance ‘å bouger en chantant. En gros, un com-

presseur sert à réduire la dynamique d’un signal. Cette tech-

nique permet en outre de maîtriser des instruments tels que

des guitares, des basses ou un piano acoustique. Par ailleurs,

une grosse caisse, caisse claire, voire des toms, sans compres-

seur ont tendance à manquer d’impact. La fonction

d’écrétage, par contre, vous aidera à protéger vos enceintes

contre des signaux quelque peu intempestifs, ce qui cause

parfois des dégâts.

Que vous ayez besoin d’un “correcteur de signal”, d’un

dompteur ou d’un instrument créatif, le GC2020C n’est pas

prêt à vous décevoir. Vous avez fait un excellent choix.

Afin de tirer pleinement parti de votre GC2020C, nous vous

conseillons de lire ce manuel dans son entièreté et de le con-

server en lieu sûr.

GC2020C Compresseur/Limiteur Mode d’emploi

ii

Précautions

Evitez toute exposition à une chaleur,
une humidité, une quantité de
poussière et de vibrations excessives

Evitez de placer l’appareil dans un lieu exposé à des tempéra­tures élevées ou une forte humidité (évitez la proximité de
radiateurs, poêles, l’exposition au soleil, etc.). De même, les
endroits poussiéreux ou sujets à des vibrations sont à proscr­ire pour éviter tout endommagement.

Evitez les chocs

Des chocs violents peuvent endommager l’appareil.
Maniez-le avec soin.

Veillez à laisser assez d’espace autour de l’appareil pour
garantir une bonne ventilation.

Gardez au moins un espace de 10 cm entre l’arrière de l’appa­reil et le mur. Cela évitera toute accumulation interne de
chaleur qui risquerait de provoquer une surchauffe de
l’appareil et éventuellement un incendie.

N’ouvrez pas le boîtier de l’appareil
et n’essayez pas de le réparer ou le
modifier vous-même.

Ce produit ne contient aucune pièce réparable par l’utili­sateur. Adressez-vous pour tout entretien ou réparation à un
SAV agréé par Yamaha. Si vous ouvrez l’appareil et/ou
touchez aux circuits internes, vous perdez le bénéfice de la
garantie.

Assurez-vous que l’appareil est hors
tension avant d’effectuer ou de
supprimer des connexions

Mettez toujours les appareils concernés hors tension avant de
brancher et de débrancher des câbles. C’est vital pour éviter
d’endommager l’appareil ainsi que tout autre matériel qui y
est relié.

Maniez les câbles avec précaution

Branchez et débranchez toujours les câble (ainsi que le cor­don d’alimentation) en tirant sur la prise et non sur le câble.

Nettoyez avec un chiffon doux et sec

N’utilisez jamais de solvants tels que de l’essence ou de la
térébenthine pour nettoyer l’appareil. Essuyez-le avec un
chiffon doux et sec.

Utilisez toujours une source d’alimen­tation adéquate

Assurez-vous que la tension spécifiée à l’arrière de l’appareil
correspond à celle de vos prises secteur:

Modèle USA & canadien: 120V CA, 60 Hz
Modèle général: 230V CA, 50 Hz
Modèle pour la Grande-Bretagne: 240V CA, 50 Hz

Sommaire

Qu’est-ce qu’un Compresseur/Limiteur? . . 1

Fonctions du Compresseur/Limiteur . . . 1
Paramètres du Compresseur/Limiteur . . 2

Réglage du Compresseur/Limiteur . . . . . 4

Qu’est-ce qu’un Expandeur/Gate? . . . . . . . 5

Réglage de l’Expandeur/Gate . . . . . . . . . 5

GC2020C Compresseur/Limiteur Mode d’emploi

Commandes & connexions . . . . . . . . . . . . 6

Face avant . . . . . . . . . . . . . . . . . . . . . . . 6

Face arrière . . . . . . . . . . . . . . . . . . . . . . 7

Caractéristiques techniques . . . . . . . . . . 8

Dimensions . . . . . . . . . . . . . . . . . . . . . . 9

Schéma . . . . . . . . . . . . . . . . . . . . . . . . 10

Qu’est-ce qu’un Compresseur/Limiteur?

Qu’est-ce qu’un Compresseur/Limiteur?

Cette section décrit les fonctions principales du Compresseur/Limiteur ainsi que ses paramètres, sa procédure d’installation et
les effets Expandeur/Gate.

Fonctions du Compresseur/Limiteur

Compresseur

Généralement, un compresseur sert à faire passer un signal
important dans un espace restreint. Plus spécifiquement,
lorsque la plage dynamique du signal audio original est plus
importante que ce que le matériel de reproduction est capa­ble de gérer, un compresseur peut réduire la plage dynami­que du signal pour l’adapter aux limites de l’appareillage de
reproduction ou d’enregistrement. Cela doit bien sûr se faire
sans ajouter de distorsion au signal même.

La compression se mesure selon un taux: le taux de com­pression. Ce taux donne l’étendue du changement subi par
le signal apparaissant à la sortie du compresseur par rapport
au signal original. Si aucune compression n’est appliquée et
si le signal d’entrée double de niveau, le signal de sortie dou­blera également de niveau, suivant scrupuleusement le
moindre changement du signal original. Ce réglage corres­pond à un taux de compression de 1:1 (un changement de 1
du signal d’entrée produira un changement 1 à la sortie),
soit pas de compression. Si vous utilisez de la compression,
vous observerez un changement plus petit du signal à la sor­tie pour un changement égal à l’entrée. Ainsi, un taux de
compression de 2:1, par exemple, signifie que le signal de
sortie ne sera modifié que de moitié par rapport au signal
d’entrée. Exprimé en décibels, un taux de compression de
20:1 signifie que qu’un changement de 20 dB du signal
d’entrée ne produirait qu’un changement de 1 dB du niveau
du signal de sortie. Un compresseur est donc capable de
réduire la plage dynamique d’un signal audio de n’importe
quelle manière.

Voyez “Illustration 1”.

(dB)

Niveau du signal de sortie

0

Niveau du signal entrant

COMPRESSION

1:1 PAS DE COMPRESSION

COMPRESSION 2:1

Threshold (seuil)

(dB)

Limiteur

Un limiteur est en fait un compresseur à taux de compres-

sion extrême, réglé pour n’affecter que les signaux au-delà

d’un certain seuil. C’est particulièrement pratique pour ne

limiter que les crêtes qui excèdent la capacité de traitement

du matériel en question sans toucher au reste du signal.

Voyez “Illustration 2”.

(dB)

Seuil d’écrétage
(Limiter)

Niveau du signal de sortie

0

Niveau du signal entrant

ECRETEUR (LIMITER)

Illustration 2

Imaginons que nous voulions limiter les crêtes d’un pro-

gramme à un maximum de 0 dB afin d’éviter la saturation et

la distorsion lors d’un enregistrement. Réglons d’abord le

niveau “seuil” sur 0 dB (le niveau seuil est le niveau qui

enclenche le limiteur lorsque le signal d’entrée l’atteint).

Ensuite, il faut régler la compression maximale (ou presque)

disponible —

∞

:1 (compression infinie). La compression
infinie signifie qu’il n’y a absolument aucun changement du
niveau de sortie quels que soient les changements du niveau
d’entrée. Le signal sera donc inchangé tant qu’il reste sous le
niveau seuil (0 dB) tandis que les signaux dépassant ce seuil
seront émis au niveau seuil mais n’iront pas plus haut. Dans
ce cas, aucun signal excédant 0 dB n’apparaîtra à la sortie du
limiteur. Le signal audio n’est donc pas modifié, il garde sim­plement son niveau moyen (r.m.s.) dans des limites définies.

(dB)

1

Français

Illustration 1

GC2020C Compresseur/Limiteur Mode d’emploi