Allen&Heath PA28 - Manual (Page 19)

PA User Guide 19
EQUALISER
The stereo equaliser allows independent
adjustment of the low and high frequency bands.
HF
The high frequency band has a shelving response that
cuts or boosts the higher (treble) frequencies by up to 15dB. It
has most effect from 12kHz and higher.
LF
The low frequency band has a shelving response that cuts
or boosts the lower (bass) frequencies by up to 15dB. It has
most effect from 60Hz and lower.
The EQUALISER is based on the classic Baxendall
design similar to that found in audiophile hifi systems. Its
shelving response has an increasing effect as it approaches
the low and high frequency extremes.
☺
Using the equaliser It is best to keep the adjustments
made using the equaliser as small as possible. Avoid the
temptation to excessively boost the low and high ends to
compensate for poor speaker frequency response. This simply
overworks the amplifiers with little audible improvement from
the speakers. Using cut rather than boost is often more
effective in improving the clarity of the signal. For example, use
HF cut to quieten a hissy keyboard, some LF and HF cut to
shape a reverb return, and LF to cut back low frequency hum
or resonance. On the other hand, a small amount of HF boost
can brighten up a dull recording, or add some ‘air’ to keyboard
string sounds.
AUX SENDS
The stereo channel aux sends function in
the same way as described previously for the mono channels.
Note that the L and R signals are summed together to produce
a mono send for each of the four auxes.
BAL
Adjusts the level balance between the L and R signals.
At its extreme ends one signal is fully off, the other fully on.
The control has a 3dB attenuation at its centre position to
ensure equal total power as the balance is adjusted.
MUTE, PFL, PK! And FADER
Function in the
same way as described previously for the mono channel. Note
that the stereo signal is summed to produce a mono PFL feed.
The PK! Indicator senses the higher of the L and R signal
levels. The fader controls the L and R signals together.
To avoid loud clicks or unexpected noises always
mute the channel before plugging or unplugging the inputs.
Use PFL to set the channel gain before raising the channel
fader and sends.
10k 1kHz 100 30k 10
LF HF
STEREO EQ
-15
-20
-10
-5
0dB
+5
+10
+15
+20
+15 -15
60Hz
12kHz
+6
+15
+6
+6
O
-15
O
O
O
O
O
=
+6
R
O
L
O
PK !