Mono Input Channel - ALLEN & HEATH GL3800 User Manual

The MONO Input Channel
+48V
POLARITY
LINE
(PAD)
0
30
40
20
GAIN
50
-14 6 60 40
HPF
100Hz
HF
12k
-15 +15
3k
1k 4k
700 6k
500Hz 15k
HM
-15 +15
180
70 250
45 400
35Hz 1k
LM
-15 +15
LF
80Hz
-15 +15
EQ IN
AUX
1
O O +6
AUX
2
PRE-EQ PRE-EQ
AUX
3
O O +6
AUX
4
+6
O O
POST
PRE
AUX
5
O O +6
AUX
6
+6
O O
AUX
7
+6
OO
AUX
8
OO +6
POST
PRE
AUX
9-10
STEREO
+6
OO
=
PAN
L R
POST
PRE
=
PAN
L R
ODD EVEN
MUTE
PFL
PK!
+6
0
SIG
10
M
5
L-R
0
1-2
5
3-4
10
5-6
7-8
20
M1
30
M2
M3
00
M4
16
+48V
Switches +48VDC to the channel input XLR for powering
microphones or DI boxes that need phantom power. The power is
current limited through 6k8 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.
POLARITY
Reverses the polarity (+ and – connections) of the
input source. Useful when using the 'above/below' mic technique, for
example when miking a snare drum with two microphones, or for
correcting mic placement and cable wiring errors.
LINE (PAD)
Press this switch to select the channel TRS jack LINE
input. Release the switch to select the XLR MIC input. The XLR
normals through the TRS socket. With nothing plugged into the line
input the switch therefore becomes a PAD for the mic XLR. It
attenuates the input signal by 20dB for connection to high level
microphone or line sources. This gives the mic preamp a 74dB range
and headroom of +34dB to deal with the hottest signals.
GAIN
Adjusts the input sensitivity to match the connected source to
the internal 0dBu operating level of the channel. Provides a variable
54dB range from +6 to +60dB gain (mic), or -14 to +40dB (line,
padded mic). The gain should be set so that the channel meters
average '0' with loudest moments lighting '+6'. Reduce gain if the red
peak indicator lights.
Important note on setting channel levels: Use PFL to set the GAIN
controls for correct signal level through each channel. The main LR
meters provide a high resolution display of the channel signal level.
Use the faders to balance each signal in the mix. To ensure optimum
gain structure we do not recommend the practice of setting the faders
to '0' and mixing using the GAIN controls.
HPF
Switches in the channel high pass filter.
frequencies below 100Hz by 12dB per octave. The filter is pre-insert,
pre-EQ. Select the HPF to reduce low frequency noise such as
microphone popping, stage noise and tape transport rumble.
EQ
A responsive 4-band semi parametric EQ (equaliser) provides
independent control of four frequency bands. Use EQ IN to compare
the sound with the equaliser switched in or out of circuit.
HF and LF are shelving filters which affect high frequencies above
12kHz, and low frequencies below 80Hz respectively. HM and LM are
bell shaped peak/dip filters which affect frequencies around a centre
point which can be swept from 500Hz to 15kHz, and 35Hz to 1kHz
respectively. These have a width (Q) of 1.8 which provides effective
control for both creative and corrective equalisation. The EQ curves
shown opposite display the signal level response at maximum boost
and cut as the frequency varies from low (20Hz) to high (20kHz).
All bands can be boosted or cut by up to 15dB and have a centre
detent 0dB position. The overlapping frequency ranges let you deal
with challenging source problems easily using combinations of bands.
Check that you are using the best microphone type and placement
before using the EQ. Start with the EQ set flat and apply only as much
boost or cut as is really needed.
frequencies cut rather than boost where possible.
This attenuates
When dealing with problem
GL3800 User Guide