Allen&Heath ML4000 USER GUIDE - Manual (Page 22)

22 ML4000 User Guide
MONO INPUT and EQ
+48V. Switches +48VDC to the channel input XLR
for powering microphones or DI boxes that need
phantom power. The power is current limited
through 6800 ohm resistors to pins 2 and 3.
WARNING Do not connect unbalanced
sources or cables to inputs with phantom power
selected. To avoid loud clicks always mute the
channel before switching +48V on or off and
when plugging or unplugging microphones.
GAIN. Adjusts the input sensitivity to match the
connected source to the internal 0dBu operating
level of the channel. Provides a variable 50dB
range from +10 to +60dB gain. The gain should be
set so that the channel meter averages ‘0’ with
loudest moments lighting ‘+6’. Reduce gain if the
red peak meter lights.
PAD. Attenuates the input signal by 20dB for
connection to high level microphone or line sources.
When pad is selected the gain control adjusts from
–10dB attenuation to +40dB gain.
POLARITY. Reverses the polarity of the input
signal. This is used to correct reverse wired cables
or sources, and can be effective in reducing
phasing problems between microphones or acoustic
feedback between the microphone and
loudspeakers.
HPF FREQUENCY. Adjusts the cut off frequency
of the high pass filter between 20Hz and 400Hz to
reduce low frequency source noise. The filter
attenuates frequencies below cut off by 12dB per
octave.
HPF IN. Switches the high pass filter in or out.
When switched out the response extends to lower
than 10Hz.
Using the Filter
Switch in the filter and adjust the cut off frequency
to clean up sources that do not have much bass
content, for example drum kit overheads (set to
400Hz), reduce proximity popping on vocals (set
around 150Hz), reduce handling noise and stage
rumble, or protect the speakers from very low
frequency energy (set around 30 to 50Hz). Switch
out to preserve full sub energy for low frequency
sounds such as kick drum, bass and special effects.
10k 1kHz 100 30k
-35
-40
10
-30
-25
-20
-15
-10
-5
0dB
+5
+10
20Hz 400Hz
HIGH PASS FILTER
PAD
LF
-15 +15
EQ IN
LM
90
-15
50
20Hz
+15
130
200Hz
-15
80
35Hz
45
180 +15
300
Q
1k
450
5k 1k
500Hz
700 7k
15k
Q
HM
2kHz
-15
3k
20kHz
HF
+15
GAIN
7k
3k
20Hz
30
10k
IN
300
400
60
20
10 - 10
100
50
20dB
40
40
+48V