Allen&Heath PA28 - Manual (Page 25)

PA User Guide 25
MONO OUT LEVEL
This is the master
control for the console mono output. The LR mix is
summed after the LR faders to produce the mono
signal. Use the control to adjust the balance
between the LR and MONO feeds. Once set, use
the LR fader as the house volume control affecting
the LR and MONO outputs. The control ranges from
fully off to +6dB boost above its unity gain position.
SUB FILTER
Press to switch in the 100Hz low
pass filter. This is a built-in crossover filter to
condition the mono output for driving a sub bass
amplifier/speaker. Frequencies above 100Hz are
rolled off at 12dB per octave. The switch is recessed
to prevent accidental operation once set. Use a pen
or sharp object to change its position.
Sub bass speakers are large coned drivers,
typically 15” or 18”, built into reasonably large
cabinets designed to reproduce the very low
frequencies. They are referred to as ‘subs’. They
are not used by themselves. Smaller speakers often
referred to as the ‘tops’ are added to reproduce the
mid and high frequencies. Without a filter the sub
can reproduce frequencies as high as 500Hz or
more. This can cause a sub/top combination to
sound ‘boxy’ or ‘muddy’. For this reason a filter is
added to cut frequencies above the required
frequency range, usually around 100Hz. This filter
may be built into the sub cabinet, its amplifier or a
separate crossover unit. The PA Series adds the
switchable 100Hz filter for situations where no filter is
provided. Check your sub speaker instructions to
see if it is needed.
Background Music (BGM)
The console
provides a facility for playing an independently
controlled stereo music source such as CD through
the house speakers while the main LR faders are off.
This is ideal during walk in or while taking a break
during intermission.
BGM
Routes the 2-track input to the LR outputs
after the master fader but before the mute switch.
This means that the signal is not affected by the
fader but is turned off when MUTE is pressed. A
large green LED lights when BGM is selected.
2TRK TO LR
Controls the level of the 2 track
signal to the LR output from fully off to +6dB boost
above ‘0’. It has no effect if the BGM switch is off.
To avoid feedback do not use BGM if you
are using the 2-track input to monitor a recording
being made from the LR mix.
2TRK OUT
Selects the 2-track output feed to
be pre or post LR faders. It affects both the
analogue and digital (SPDIF) outputs. In its normal
up position the source follows the fader movements.
When the switch is pressed, the LR faders can be
used as the house PA volume control without
affecting the recording. The switch is recessed to
prevent accidental operation once set. Use a pen or
sharp object to select its position.
Console Monitor
The PA Series monitor
system lets you listen to the various console signals
using headphones, and check levels on two large
LED bar meters. Using the monitor does not affect
the main outputs.
HEADPHONES LEVEL
Controls the
volume of the selected monitor source in the
headphones. It does not affect the level displayed
on the meters.
WARNING: To prevent damage to your
hearing start with the headphones level set to
minimum. Avoid continued high listening levels
in the headphones or any other earpiece.
LR/2TRK
Selects the normal headphones and
meter monitor source. In its up position the post-
fade LR signal is selected. When pressed, the 2-
track input is monitored. Pressing any PFL or AFL
button automatically overrides this selection.
PFL/AFL LED
A large red LED indicator lights
to warn you when a PFL or AFL has been selected.
METERS
A pair of 12 segment LED bar meters
displays the level of the selected monitor source.
The LR mix and 2-track input are displayed in stereo,
and PFL/AFL signals in mono on both bars.
PFL stands for Pre-Fade Listen. It is used on
the inputs so that you can check the signal while the
channel is muted or its fader down.
AFL stands for After Fade Listen. It is used
on the outputs so that you can check the signal
exactly as it is at the console outputs.
☺
Using PFL and AFL 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. Use AFL when
you need to check one of the foldback mixes. You
should hear the signal in your headphones and see
its level displayed on the console meters. Adjust the
gain and mix controls so that the meters read an
average ‘0’ with loudest peaks no more than ‘+6’.
10k 1kHz 100 30k
-35
-40
10
-30
-25
-20
-15
-10
-5
0dB
+5
+10
100Hz
MONO SUB FILTER