LA Audio GCX20 User Manual

DUAL COMPRESSOR

NOISE GATE

OPERATION MANUAL

Version - 1 April 2000

CONTENTS

1. Introduction Page 3

2. Installation Page 4

2.1 Inspection and un-packing

2.2 Operating environment

2.3 CE standards

2.4 Power requirements

2.5 Signal levels

2.6 External connections

3. Warranty Page 7

4. Description of controls Page 8

4.1 Gate section Page 8-9

4.2 Compressor section Page 9-10

5. Applications Page 11

5.1 Compressor applications` Page 11-12

Limiting PA systems
Preventing tape and digital overload
Signal levelling
Fattening bass drum sounds
Bringing sounds forward in the mix
Vocal de-essing

5.2 Noise-Gate applications Page 12-13

Reducing background noise
Tightening percussion sounds
Improving mic separation
Feedback avoidance
Modifying signal decay

5.3 Other applications Page 13

Line amplifier

6. Circuit description Page 14

7. Specifications Page 15

Page 2

1.0 INTRODUCTION

The GCX20 is a dual channel soft knee compressor and fast acting noise
gate. The compressors have fully variable Threshold and Ratio, two auto
attack/release modes for solo instruments or program mixes and sidechain
inserts for frequency conscious compression.

The two integral noise gates have variable Threshold and Release.

The compressors and gates can be linked for stereo operation and the
true RMS summing side chain of the GCX20 ensures perfect stereo
imaging.

The facilities provided by the GCX20 are summarised as follows:

The two Gate sections feature -

• Variable Threshold and Release

• Fast attack

• Stereo linking

• Gate threshold LED

• Side chain insert for connection of an external equaliser

• Balanced inputs and outputs on XLR and TRS jack connectors

The two Compressor sections feature -

• Soft knee compression.

• Two Auto Attack/Release modes

• Variable Threshold, Ratio and Gain

• Gain reduction metering

• Stereo linking

• Side chain insert for connection of external equaliser

• Balanced inputs and outputs on XLR and TRS jack connectors
Typical Gate applications include:

• Reducing background noise

• Tightening percussion sounds

• Improving mic separation

• Feedback avoidance

• Modifying signal decay

Typical Compressor applications include:

• Limiting PA systems

• Preventing tape and digital overload

• Signal levelling

• Fattening bass drum sounds

• Bringing sounds forward in the mix

• Vocal de-essing

Page 3

IMPORTANT: PLEASE READ THIS SECTION BEFORE USING THE GCX20

2.1 INSPECTION AND UNPACKING

The GCX20 has been carefully packed at our factory in a carton designed
to withstand handling in transit. Should the unit appear to have been
damaged in transit notify your dealer immediately and do not discard any
of the packing. The carton should contain -

• The GCX20 unit

• Power cord

• Operator Manual (this book)

2.2 OPERATING ENVIRONMENT

The GCX20 is designed to operate between 0 and 50°C (32-122°F) with
relative humidity no more than 80%. Should the unit be installed in an
equipment rack, ensure that the ambient temperature conforms to these
levels.

2.3 CE STANDARDS AND THE LOW VOLTAGE DIRECTIVE (LVD)

The GCX20 has been designed to meet the latest Electromagnetic
Compatibility (EMC) regulations. However we recommend you do not
operate the unit close to strong emitters of electromagnetic radiation such
as power transformers, motors, mobile telephones or radio transmitters.

The unit should only be connected to a power supply of the type described
in 2.4 POWER REQUIREMENTS or as marked on the unit. The unit must
be earthed for safe operation. Disconnect the mains supply before
removing any cover.

2.4 POWER REQUIREMENTS

There is a mains fuse located inside the unit which is accessed by
removing the cover. This fuse is for protection against unit faults and as
such will not normally need replacing. If you think you have a power
related problem please refer to your dealer.

The voltage and fuse rating have been factory set for -

230V 50mA UK
220V 50mA Republic of Korea
115V 100mA North America

• The correct voltage and fuse rating is indicated on the rear panel.

• Please check that your unit is correctly rated for the voltage of
the country of operation.

2.0 INSTALLATION

Page 4

If the fuse requires changing at any time please ensure the correct fuse is
fitted. An incorrect fuse could cause damage to the unit and may constitute
a fire hazard.

If you carry your GCX20 from one country to another it is very important to
ensure the voltage is compatible.

For your information the unit can be internally rewired for use in 230V, or
110-125V countries - contact your dealer for information. A special 100V
version is available for Japan and a 220V, 60Hz version for Republic of
Korea.

The mains lead connections to the appliance are coloured in accordance
with the following code:

Green-and-Yellow Earth

Blue Neutral
Brown Live

• WARNING: THIS APPLIANCE MUST BE EARTHED

2.5 SIGNAL LEVELS

The GCX20 will accommodate both -10dB and +4dB operating levels
without the need for level switching.

PLEASE NOTE: the XLRs are set for +4dBu and the TRS jacks for -

10dBV operating levels. Use the appropriate connector/level to interface
between your equipment and the GCX20.

Using the TRS jack input with +4dB signal levels m ay in some set-ups will
over drive the GCX20 and cause distortion.

The GAIN control on the compressor section allows -20dB to +20dB of
level adjustment which should allow the GCX20 to interface to most
equipment types.

Signals in excess of +20dB will cause the unit to distort.

2.6 EXTERNAL CONNECTIONS

The input and outputs of the GCX20 are balanced on both XLR and 1/4"
TRS jack connectors. For balanced input and outputs, connections to the
unit should be wired as follows:

XLR +4dBu Pin 1 Screen (Signal ground)
Pin 2 Hot (+ve)
Pin 3 Cold (-ve)

For un-balanced operation join pins 1 and 3 on either input or output.

TRS jack -10dBV Tip Hot (signal +)

Page 5

Ring Cold (signal -)
Sleeve Screen (signal ground)

For un-balanced operation join Ring and Sleeve on either input or output.

Fig 2.6.1 GCX20

rear view showing Input and Output connections

Page 6