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Valve input channel, Channel 1 valve, Drive – Allen&Heath GS-R24M User Manual

Page 21: Gain control, Drive control, Level control, Bus routing switches, After fade listen switch, Allen & heath 21 gs_r24 user guide, Afl m l-r 1-2

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Allen & Heath 21 GS_R24 User Guide

Gain Control

This adjusts the gain of the input amplifier to match the signal level

of the input. The gain is varied from +6dB to +60dB for signals
plugged in to the xlr socket (Mic Input) and –14dB to +40dB for

signals plugged into the Line/Inst input jack (without Boost being

pressed).
The Gain control does not affect the signal if the input is sourced

from the DAW interface.

Drive control

The Drive control determines the amount of signal that passes

through the valve stage and therefore the amount of signal with
thermionic valve pre-amp characteristic. In addition to increasing the

amount of even harmonic content, the volume level may also be in-

creased when swept towards the MAX setting.
A 3 colour LED indicator illuminates green, orange then red to show

the signal level after the valve stage.

VALVE INPUT CHANNEL

60 40

-14 6

30

40

50

0

20

GAIN

MIN

MAX

Drive

Channel 1

Valve

10

-30

-20

-5

0

5

-10

LEV

L

R

PAN

AFL

M

L-R

1-2

BUS

3-4

0.00 ms

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

1.80

1.99

-8.70

-6.53

-4.35

-2.18

0.00

2.18

4.35

6.53

8.70

V

0.00 ms

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

1.80

1.99

-8.70

-6.53

-4.35

-2.18

0.00

2.18

4.35

6.53

8.70

V

Drive control characteristics at around +10dBu. Two graphs show MIN then MAX

0.00 ms

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

1.80

1.99

-17.40

-13.05

-8.70

-4.35

0.00

4.35

8.70

13.05

17.40

V

The third graph shows extreme
overload characteristics of the

combined instrument input and

valve stage with maximum drive.

Note the asymmetric soft clipping
on each half-cycle.

Level control

Effectively the fader for the valve channel (or master volume). Ad-

justs the level from fully attenuated to +10dB of gain.

PAN

The pan control adjusts how the signal from the mono input channel

is shared between the left and right buses and between odd and
even group buses.

Bus Routing Switches

The routing switches connect the channel signal to the mix
buses in a similar way to the mono input channel.

After Fade Listen switch

Connects the post level control signal in mono to the AFL
monitoring system.
A full description of the console monitoring system is given on
page 29.

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