T L Audio CRIMSON C-3021 User Manual

T L Audio

CRIMSON SERIES

User Manual

C-3021 COMPRESSOR

Tony Larking Professional Sales Limited,

Letchworth, England.

Tel: [phone]. International [phone].

Fax: [phone]. International [phone].

INTRODUCTION

The T L Audio Indigo Series utilises low noise solid state circuitry to produce audio
processing units offering very high quality signal paths with comprehensive control
facilities. The Crimson Series are straight-forward to operate, and offer excellent value
for money.

The C-3021 is a two channel compressor. It may be operated as two independent
mono channels or as a full stereo compressor, with ganging of controls and combined
control voltages. All parameters of the compressor are variable, and a bargraph meter
may be used to display output level or gain reduction.

The block diagram of the unit is shown in fig.1. Each channel has three input sources ­a balanced line level input via an XLR connector, an unbalanced line level input via a
jack socket, and an instrument input also on an unbalanced jack socket but located on
the front panel where it provides a convenient means of patching a guitar or keyboard
directly into the compressor. All three inputs may be used simultaneously. The gain of
the input stages is controlled by a centre-detented control, calibrated for 0dB nominal
gain from the line input sources at the centre and providing +/-20dB of variation. The
instrument input has a sensitivity switch associated with it, to match the gain to a low
level pickup (e.g. a passive guitar or microphone) or a higher output source such as a
keyboard or active guitar, followed by the 40dB variation of the input gain control

After the input stages, the signal is fed to the compressor core and the sidechain
processing. The sidechain also monitors the output of the compression stage, and
generates a control signal which varies the attenuation of the compressor. The
sidechain processing includes fully variable control of the compressor threshold and
ratio, plus switched fast and slow time constants for attack and release. Frequency
dependant compression (for example de-essing) may be achieved by placing an
equaliser into the sidechain insertion point.

The channel B sidechain controls normally operate independently, but the
comprehensive stereo mode offered by the C-3021 allows the channel A controls to be
used for both channels A and B, ensuring accurate tracking and easy adjustment of the
parameters. Stereo mode also combines the compressor cell control signals, which
always applies the same amount of gain reduction to both channels, thereby preserving
the stereo image.

Independent gain make-up controls are provide, to retain the subjective loudness of a
compressed signal. Each channel has a balanced line level output on an XLR socket,
and an unbalanced output on a jack socket. Twin LED bargraph meters are provided,
which may be switched to monitor the output signal level or compression applied.

Please read this manual fully before installing or operating the Compressor.

PRECAUTIONS

The T L Audio C-3021 Compressor requires very little installation, but like all
electrical equipment, care must be taken to ensure reliable, safe operation. The
following points should always be observed:

- All mains wiring should be installed and checked by a qualified
electrician,

- Ensure the correct operating voltage is selected on the rear panel
before connecting to the mains supply,

- Never operate the unit with any cover removed,

- Do not expose to rain or moisture, as this may present an electric
shock hazard,

- Replace the fuse with the correct type and rating only.

Warning: This equipment must be earthed.

INSTALLATION

AC Mains Supply.

The unit is fitted with an internationally approved 3 pin IEC connector. A mating
socket with power cord is provided with the unit, wired as follows:

Brown: Live.

Blue: Neutral.

Green/Yellow: Earth (Ground).

All mains wiring should be performed by a qualified electrician with all power
switched off, and the earth connection must be used.

Before connecting the unit to the supply, check that the voltage selector switch on the
rear panel is correctly set. The unit may be set for 115V (accepting voltages in the
range 110V to 120V, 60Hz AC), or to 230V (for voltages in the range 220V to 240V,
50Hz AC). Adjustment to the operating voltage should be made by sliding the selector
switch left or right with a small screwdriver until the desired voltage is displayed. The
mains fuse required is 20mm anti-surge, 1AT rated at 250V. If it ever necessary to
replace the fuse, only the same type and rating must be used. The power consumption
of the equipment is 30VA.

Warning: attempted operation on the wrong voltage setting, or with an
incorrect fuse, will invalidate the warranty.

Audio Operating Level.

The compressor is equipped with inputs and outputs suitable for connection to a wide
variety of other audio equipment. Generally, the balanced XLR connections will be
required for interfacing to other professional equipment, where the operating level
(line-up level or nominal level) will be +4dBu, or about 1.2V rms. The unbalanced
jack connectors are generally intended for interfacing to semi-professional equipment
and have an operating level of -10dBu, or about 225mV rms.

The compressor may be used to change between operating levels, for example by
connecting the unbalanced output of a semi-pro mixing console to the compressor’s
unbalanced input, and taking the balanced output of the compressor to the balanced
input of a tape machine at +4dBu. All inputs and outputs of the compressor may be
used simultaneously if required. Balanced interconnection is always preferable to
obtain the best headroom and noise rejection, but can only be used if the other
equipment in the chain, e.g. the mixing console, also has provision for balanced
connections.