Bedienungsanleitung Allen-Heath PA-CP Series (Seite 17 von 36) (Englisch)

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PA-CP User Guide 17

PAN Adjusts the stereo position of the channel

signal in the main LR mix. At the centre position

equal signal is sent to the L and R outputs. Fully

anticlockwise all the signal routes to L and none to

R, and fully clockwise the reverse is true. The

control has a 3dB attenuation at its centre position.

This ensures equal power as the sound is panned

from one side through the centre to the other side. It

also has a mechanical detent to help you find its

default centre position quickly.

☺ Using PAN If you are working with a stereo PA

system use PAN to set the position of each signal in

the mix. In live sound mixing it is best to set pan

centre or close to centre for most signals so that all

listeners hear a similar balance regardless of their

position in the room. Sounds such as kick drum,

bass and lead vocal would usually be set centre.

Ambient or backing sources may be panned slightly

to spread the image. Stereo sources such as

backing tracks, keyboards and sound effects may

be panned fully or use the stereo channels instead.

If you are working with a mono PA system simply set

all pan controls centre.

MUTE Press this switch to turn the channel

signal off. The large red LED lights to warn that the

channel is muted. Mute affects the channel pre and

post-fade sends. This ensures that the feeds to the

foldback monitors, effects, aux and house mix are

turned off when the channel is muted. It does not

affect PFL. You can still use PFL to check the signal

while the channel is muted.

To avoid loud clicks or unexpected noises

always mute the channel before plugging or

unplugging microphones and other sources.

PFL Press this switch to listen to the channel

signal in the headphones and display its level on the

main meters. This lets you check each channel

signal independently without affecting the outputs.

PFL is sourced pre-fader, pre-mute. Pressing PFL

automatically overrides LR or 2TRK in the

headphones. The channel PFL switch LED and the

big PFL/AFL indicator below the main meters light to

warn that PFL has been selected.

 PFL stands for Pre-Fade Listen. It sends the

signal taken just before the channel mute switch and

fader to the engineers personal headphones monitor

and console meters. This means that you can check

the signal while the channel is muted or its fader

down. Note that AFL, as found on the FB1 and FB2

masters stands for after-fade listen.

☺ Using PFL Use PFL to check sound quality

and the channel gain setting when plugging in

different sources or when you suspect a change or

problem with a particular signal. During sound

check start with the channel muted. This lets you

set up the signal before you introduce it into the

monitors and house mix. Press PFL. You should

hear the signal in your headphones and see its level

displayed on the console meters. Adjust the gain

control so that the meters read an average ‘0’ with

loudest peaks no more than ‘+6’.

PK! The PFL switch LED also provides a channel

signal peak indication. The indicator lights brightly

when the pre-fade signal reaches +16dBu. This

means that it lights 5dB before clipping to give you

the chance to reduce the signal before you hear any

distortion. If the PK! Indicator flashes turn back the

channel gain control until it stops.

FADER A 100mm smooth travel fader adjusts

the signal level feeding the main LR mix, AUX and

FX sends. It provides up to +10dB boost above its

normal unity gain ‘0’ position, and shuts off fully

when pulled back to its bottom position.

☺ Using the faders These are your main mixing

controls. Use the channel faders to adjust the level

of each signal in the mix. Normal operating position

for dominant sounds is around the ‘0’ mark, with the

quieter backing sounds typically in the range ‘0’ to ‘-

20’. The +10dB boost is there to give you a bit extra

when you need it. If you find your normal setting is

near maximum fader position or well below ‘0’ then

use PFL to check that the gain is correctly set.

 The fader scale is graduated in dB (decibel)

markings. The dB is a measurement of gain. It

relates the fader output level to its input level. If the

output is the same as the input then the gain is 0dB.

That is why the fader is marked ‘0’ at its normal

operating position, the point at which all the channel

signal is fed to the mix. If the fader is moved above

‘0’ it produces more output and therefore has gain

boosting the signal level up to a maximum of

+10dB. As the fader moves below ‘0’ it produces

less output than its input and therefore has

attenuation. The -5, -10, -20 and -30dB attenuation

positions are marked. The infinity mark at the

bottom position represents maximum attenuation, in

other words the signal is turned off.

 The dB explained Because of the way the

human ear responds to sound, the decibel uses a

logarithmic rather than linear scale. Regarding

audio voltages, dB = 20log(Vout/Vin) where Vout is

the output level expressed as a voltage, Vin the input

level. You can see that 0dB is the result when the

Vout is the same as Vin. This is also referred to as

‘unity gain’, or gain of 1x. For rule of thumb, gain is:

+10dB = 3x at fader top

+6dB = 2x

0dB = 1x (unity)

-6dB = 0.5x

-10dB = 0.3x

-20dB = 0.1x

-30dB = 0.03x

-90dB = 0.00003x at fader bottom

The above shows how wide the fader control range

is. At maximum position the signal is amplified three

times. At minimum position it is just 1/30000 of the

original, effectively off.

Write-on Block Use the white block for

labelling the channel using chinagraph marker, felt

pen, adhesive label or tape, or magnetic label strips.

Avoid leaving sticky residue. Do not use chemicals

or solvents to clean the blocks.

Allen-Heath PA-CP Series Seite 17

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