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MATCHING THE SIGNAL LEVELS

For best performance it is important that the connected source signals are

matched to the "normal operating level" of the console. Similarly the

console outputs should be correctly matched to the operating levels of the

connected amplifiers and destination equipment. If too high the signal

peaks will be clipped resulting in a harsh distorted sound, and if too low

the signal-to-noise ratio is reduced resulting in excessive background hiss

and noise.

For best results operate the console with the meters averaging around '0'

letting the louder passages peak into the 'yellow'. Reduce the gain if the

red peak indicators flash. The GL4000 produces a standard XLR output

level of +4dBu for a meter reading of 0VU. It is advisable to adjust the

power amplifier input gain or fit an attenuator pad if normal console

operation results in an output level too high for the connected amplifier.

Normal operation should result in fader levels around the '0' mark. Note

that when reversed with the auxes the matrix and LR2 output level trims

can be used to match the console to the amplifiers independent of the mix

levels. Similarly the group output trims can be switched in to match levels.

The GL4000 has an advanced PFL (pre-fade listen) / AFL (after-fader

listen) and channel metering system to let you listen to and check the level

of signals at different points in the signal path without affecting the main

outputs. Use the channel PFL switches to set up the input GAIN controls

to read an average '0'. Signal activity is always shown on the channel

meters regardless of fader position. The green 'SIG' LED lights at -20dBu

to indicate signal presence, the green '0' LED indicates normal level,

yellow '+6' indicates normal peaks, and the red 'PEAK' LED warns of

potential overload 5dB before clipping.

The mix meters above each output fader monitors the pre-fade mix level.

You can run the mix 'hot' but reduce the channel fader levels if the red

'PEAK' LEDs flash.

LEVEL DIAGRAM

ALLEN & HEATH GL4000 User Guide

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