Allen & Heath AP5195 用户手册

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页码 36
20 
PA User Guide 
The EFFECTS Channel 
Overview
   The PA Series features a built-in digital stereo 
effects unit.  Effects such as artificial reverberation, delay, echo 
and chorus can be selected from the 16 presets.  You can 
independently control how much effect is added to each signal 
in the mix using the channel FX sends.  The overall level of the 
effects in the LR and foldback mixes is adjusted using the 
effects channel described here.  An external input facility is 
included so that the return from an additional independently 
controlled effects unit can be mixed with the internal effects.  
Alternatively the internal unit can be switched off and the 
channel FX sends used to feed the external unit.  The channel 
can be muted using a footswitch for performer controlled 
effects bypass, for example between songs.  The effects may 
also be turned on or off, and the preset changed using MIDI. 
 
The Signal Path
   The signal flow diagrams shown here 
illustrate how the effects system works. 
 
A    Internal effects only   The channel signal is routed 
through the fader direct to the main LR mix.  A portion of the 
signal is also routed to the internal effects processor by turning 
up the channel FX send control.  As this is sourced after the 
fader, the balance between the direct and effects signal is kept 
the same regardless of fader position.  The processed signal is 
routed through the FX channel fader  back  into  the  LR  mix 
where it adds with the direct signal. 
B    Internal and external effects   Here the internal effects 
work as described above.  In addition, an external effects 
processor is patched in as shown.  The signals sent to this unit 
are independently adjusted using the channel AUX send 
controls which route it to the AUX output.  The processor stereo 
output is plugged into the EXT FX IN sockets.  GAIN matches it 
to the operating level of the channel.  The external signal sums 
with the internal effects and is routed through the FX fader to 
the LR mix.  This lets you work with two independently 
controlled effects units returned through a common effects 
master channel. 
 C    External effects only   If you prefer, you can switch off the 
internal effects processor and use its FX sends and the FX 
channel with your favourite external unit.  This way, no controls 
are wasted when the internal unit is not used. 
  
Wet and dry signals   The signal sent from the channel 
to the LR mix is referred to as ‘dry’.  This is the original signal 
with no effect added.  The portion of signal routed through the 
effects processor is referred to as ‘wet’ because it is effect only.  
Consider room reverberation:  The listener hears the voice of 
the singer (dry) and also the acoustic reflections  (wet) as the 
voice reverberates around the room.  The bigger the room the 
more reverb is heard.  The PA Series simulates reverb in the 
same way.  The reverb is created electronically using the digital 
processor (wet) and then added to the direct (dry) signal.  The 
channel FX sends determine how much reverb is added to 
each signal in the mix. 
 
Adding effects to the foldback   The above describes how 
effects are added to the LR mix which feeds the house 
speakers.  You can also add the effects to the foldback mixes 
by turning up the FX channel FB1 and FB2 controls.  The signal 
is sourced post-fade so that the fader becomes the master 
level control for the effects in the LR and foldback mixes. 
A
LR MIX
GAIN
EXT FX IN
INTERNAL
FX
FX
AUX
FX CHANNEL
+
SUM
INPUT CHANNEL
AUX SEND
FX SEND
LR MIX
GAIN
EXT FX IN
INTERNAL
FX
FX
AUX
FX CHANNEL
+
SUM
INPUT CHANNEL
AUX SEND
FX SEND
EXTERNAL
FX
B
LR MIX
GAIN
EXT FX IN
INTERNAL
FX
FX
AUX
FX CHANNEL
+
SUM
INPUT CHANNEL
AUX SEND
FX SEND
EXTERNAL
FX
C
LR MIX
FX CHANNEL
+
SUM
FB2
+ SUM
FB1
FB2 MIX
FB1 MIX