ALLEN & HEATH GS-R24 - Pre-Amp Performance Notes; HF EQ; HMF EQ

Allen & Heath 12 GS_R24 User Guide
MONO INPUT CHANNEL
HMF EQ
The HMF (High Mid Frequency) equaliser affects the upper middle of the
audible frequency range. The frequency graduations on the sweep con-
trol are the centre frequencies of the EQ. The Q factor is the width of
the equaliser curve and is variable from a wide 0.8 to a sharp 6.
HF EQ
The HF (High Frequency) equaliser affects the frequency response of the
higher audible frequencies. The corner frequency of 12kHz is around 3dB
from the maximum cut or boost of the circuit.
10.00 Hz 100.00 1000.00 10000.00
0.00010
0.00100
0.01000
0.10000
1.00000
%
Pre-Amp performance notes
The GS-R24 pre-amp is a highly developed and proven design. Originally evolved
from a balanced summing amplifier circuit originally designed back in the late
1980s for the Focusrite Forte console whilst working for industry legend Rupert
Neve. Very low noise transistors are employed in a symmetrical topology with
local phase compensation resulting in an inherently stable but wide bandwidth,
low distortion, very low noise design.
THD+n plots of pre-amp
at 10, 20, 30 and 40dB
gain showing uniformity
of distortion performance
over a wide range of gain
settings.
10.00 Hz 100.00 1000.00 10000.00 40000.00
-20.00
-15.00
-10.00
-5.00
0.00
5.00
10.00
15.00
20.00
dBr
10.00 Hz 100.00 1000.00 10000.00 40000.00
-20.00
-15.00
-10.00
-5.00
0.00
5.00
10.00
15.00
20.00
dBr
60 40-14 6
30
40
50
0
20
GAIN
HPF
100Hz
HM
0.8
6
2k
700
400Hz
1k
6k
18k
4k
Q
F
G
LM
0.8
6
120
30
18Hz
60
600
1k
300
Q
F
G
-15
LF
+15
80Hz
HF
12k
EQ IN
1
1
+48V
LINE
POL
-15 +15
-15 +15
-15 +15