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Summary of Contents for LA Audio GOC20
- Page 1 DUAL COMPRESSOR NOISE GATE OPERATION MANUAL Version - 1 April 2000...
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Page 2: Table Of Contents
CONTENTS Introduction Page 3 Installation Page 4 Inspection and un-packing Operating environment CE standards Power requirements Signal levels External connections Warranty Page 7 Description of controls Page 8 Gate section Page 8-9 Compressor section Page 9-10 Applications Page 11 Compressor applications Page 11-12 Limiting PA systems Preventing tape and digital overload... -
Page 3: Introduction
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. -
Page 4: Installation
2.0 INSTALLATION 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. -
Page 5: Signal Levels
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... - Page 6 The GCX20 side chain connectors are wired as follows - Sleeve Ring Screen Send Return Plugging into the GCX20's side chain automatically breaks the signal path to the side chain circuitry. This path must be completed by the external connected equipment. The side chain in-out signal path affects both the Compressor and the Gate response.
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Page 7: Warranty
To receive service under this warranty it is necessary to return the unit to an LA Audio authorised service centre or to the factory with a dated receipt as proof of purchase. After repair the unit will be returned to you free of charge. -
Page 8: Description Of Controls
4.0 DESCRIPTION OF CONTROLS GATE SECTION COMPRESSOR 1 GATE 1 THRESHOLD RATIO GAIN THRESHOLD RELEASE MASTER ATTACK - 10 - 10 GATE - 30 DUAL - 20 SLOW - 40 STEREO GAIN REDUCTION FAST A U D I O - 20 -15 -10 - 6 - 30 + 20 - 20... -
Page 9: Compressor Section
In LINK mode Channel 1 becomes the MASTER controller for both channels. The controls, switches and leds associated with Channel 2 are in-operative in this mode. The GCX20 combines the signals from both channels so that the input to either channel (exceeding Threshold) triggers the gate. - Page 10 Some way of restoring the signal to its pre-compressed level is required. The Gain control provides adjustment to restore output level after compression. GAIN can also be used to level match between equipment connected to the GCX20. GAIN range is - 20dB to +20dB.
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Page 11: Applications
5.0 APPLICATIONS COMPRESSOR APPLICATIONS A compressor works by applying increasing levels of attenuation (compression) to signals which exceed a set volume level. The level above which the compression occurs is called the Threshold and the amount by which the signal is compressed is governed by the Ratio. For example - With an input signal at nominal level (+4dB or -10dB according to which input connector is used), Threshold set to -10dB and Ratio set to 2:1, the signal will be compressed by 5dB. -
Page 12: Signal Levelling
Signal levelling Signal level variations can occur when the distance between the vocalist and microphone changes. The GCX20 compressor can be used to level out the result of poor microphone technique, producing an even sound. Set RATIO to around 4:1 and adjust THRESHOLD for a gain reduction of 6 to 10 dBs at maximum signal level. -
Page 13: Tightening Percussion Sounds
Slowly increase the THRESHOLD until only the required signal opens the gate. Vary the RELEASE until the desired effect is achieved, faster for percussive instruments and slower for vocals and acoustic instruments or instruments with desirable sustain. Tightening percussion sounds A drum in it's natural form will include a lot of sustain. -
Page 14: Circuit Description
6.0 CIRCUIT DESCRIPTION Audio Audio output input Sidechain Gate insert Sidechain Gain Detector Gate Threshold Release Compressor Sidechain Gain reduction Threshold Ratio Auto meter Fig: 6.0.1 Block diagram of the LA GCX20 showing the main signal paths AUDIO PATH The input signal first passes through the electronically balanced input stages and then directly to the VCA (Voltage Controlled Amplifier). - Page 15 COMPRESSOR THRESHOLD The Threshold control sets a DC reference level above which compression can start. This is compared to the RMS voltage and when this exceeds the reference the difference is forwarded to the Ratio control RATIO The difference voltage from the Threshold stage is amplified or attenuated depending on the setting of Ratio.
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Page 16: Specifications
220VAC, 60Hz, 6VA Mains connector Standard IEC receptacle MECHANICAL Dimensions 1.75" (44mm)H x 19" (482mm)W x 6.5" (165mm)D Weight Unit = 2.2kg, Shipping = 2.85kg LA Audio reserves the right to alter any feature or specification without prior notice E&OE Page 16... - Page 17 Page 17...
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