4 Channel Auto Compressor Operation Manual April 2002
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CONTENTS 1.0 OVERVIEW 4 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 2.10 DESCRIPTION OF CONTROLS Bypass switch Program switch Threshold control Ratio control Auto-Manual switch Hard-Soft Knee switch Release control Gain control Gain Reduction meter Link switch 5-7 3.0 3.1 3.2 3.3 3.4 3.5 3.6 EXTERNAL CONNECTIONS Side Chain insert Input Output Level switch Power switch Power inlet 8-9 4.0 4.1 4.2 4.3 4.
1.0 OVERVIEW Main Features: • • • • • • • 4 channels of Auto compression Soft or hard knee compression slopes Fully variable Threshold, Ratio, Release and Gain Auto Attack/Release and Program Dependant Attack with manual Release modes Low frequency Program filter Side chain inserts Balanced Inputs-Outputs with +4dBu/10dBV switching The C400 is a professional 4 channel compressor that can be operated as 4 separate processors or linked as two independent stereo pairs.
2.0 DESCRIPTION OF CONTROLS 2.1 BYPASS switch Pressing BYPASS cancels compression by removing the side chain voltage from the voltage controlled amplifier (VCA). The Input-Output and level change circuitry remain in the signal path. The BYPASS led lights when the compressor is Bypassed. 2.2 PROG. switch The PROGRAM switch inserts a low-cut filter into the side chain to remove the bass content of the program material which can cause over compression or pumping.
A RATIO of ∞:1 effectively means that there is no increase in output level once the input signal has reached THRESHOLD reference i.e. limiting. The following diagrams shows the difference between HARD and SOFT knee compression at a number of different RATIOs. THRESHOLD in the diagrams is set to 0dB. Fig 2.1: HARD knee compression 2.5 Fig 2.
HARD knee compression provides tight control over signal levels above threshold and is useful for creative applications or where a large amount of gain reduction, such as limiting, is required. 2.7 RELEASE control RELEASE is only active in MAN (manual) mode (AUTO-MAN switch in) and adjusts the release time between 40mS and 4S. 2.8 GAIN control The GAIN control on the C400 allows the output level from the compressor to be attenuated or amplified by up to 20dB.
3.0 EXTERNAL CONNECTIONS 3.1 SIDECHAIN The Side chain TRS jack allows connection of an external processor such as an equaliser for frequency sensitive compression e.g. de-essing. This is an unbalanced insert with Ring wired as Send and tip wired as return. Please note: Plugging a jack into the side chain connector breaks the control signal path which must then be completed by the externally connected equipment. 3.2 INPUT Electronically balanced Input with pin 2 wired hot (signal +).
3.5 POWER Mains power switch for C400 3.6 POWER INLET Standard IEC mains inlet for use with a detachable mains cable. See Section 3.4 for details of power requirements and fusing. Please note: The mains protection fuse is inside the unit, accessed by removing the top cover. Ensure that the unit is disconnected from the mains supply before attempting to replace the fuse.
4.0 4.1 INSTALLATION INSPECTION AND UNPACKING The C400 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 C400 • Power cord - country specific, please check • Operator Manual (this book) 4.
Please note: If the fuse requires changing at any time please ensure the correct type is fitted. An incorrect fuse could cause damage to the unit and may constitute a fire hazard. The detachable IEC mains lead connections to the appliance are coloured in accordance with the following code: Green-and-Yellow Blue Brown Earth Neutral Live WARNING: THIS APPLIANCE MUST BE EARTHED Please note: A protective earth connection, made by way of the earth conductor in the power cord, is essential for safe operation.
5.0 WARRANTY Your LA Audio C400 has been manufactured to a high standard using quality components. If correctly installed and operated the unit should give years of problem free operation. However in the event of a defect in material or workmanship causing failure of the unit within 1 year of the date of original purchase we will agree to repair, or at our discretion replace, any defective item without charge for labour or parts.
6.0 TECHNICAL SPECIFICATIONS ELECTRICAL Frequency response: Input Impedance: Maximum Input Level: Input-Output Level: 20Hz to 20kHz (+0, -0.5dB) 20k balanced +20dBu +4dBu or -10dBV Output Impedance: Max. Output Level: 100R balanced +20dBu THD: Signal to Noise Ratio: < 0.
7.0 DIMENSIONS In keeping with our policy of continuous improvement LA Audio reserves the right to alter specifications without prior notice. Manufactured in the UK by LA Audio www.laaudio.co.
