Mackie ProFX12 Owner's Manual - page 18
18
ProFX8 and ProFX12
Pr
oFX8 and Pr
oFX12
For hybrid channels (mic input and
stereo line input), the gain control just
affects the microphone input.
For stereo channels (no mic input) the
gain control just affects the line-level
inputs, with 20 dB of gain, and 20 dB of
attenuation. There is no level set LED.
20. LEVEL SET LED
These LEDs are used with the gain control [19] to set
the channel preamplifier gain just right for each source.
If one or more channels are distorting, check the level
set LEDs. If they are on continuously, turn down the
gain.
21. LOW CUT
Each channel with a mic input has a low cut switch
THATCUTSTHEBASSFREQUENCIESBELOW(ZATARATEOF
18 dB per octave. All mic inputs are affected, as well as
the line inputs of the mono channels.
We recommend using low cut on every microphone
application except kick drum, bass guitar, and bassy
synth patches. These aside, there isn’t much down there
that you want to hear, and filtering it out makes the low
stuff you do want much more crisp and tasty. Not only
that, low cut can help reduce the possibility of feedback
in live situations and help to conserve the amplifier
power.
19. GAIN
If you haven’t already, please read the gain-setting
procedure on page 3. The gain adjustment allows the
various source signals from the outside world to be
adjusted to the same optimal internal operating levels.
Setting the gain correctly will ensure that the pre-
amplifier’s gain is not too high, where distortion could
occur, and not too low, where the quieter, exquisitely-
delicate passages might be lost in background noise.
For mono channels (mic input with a
mono line input), the gain knob adjusts
the input sensitivity of the mic and line
inputs.
Adjust the gain control so the level set LEDs [20]
illuminate occasionally during the louder moments and
are off during the quieter moments.
If the signal comes through the mic XLR jack, there
will be 0 dB of gain (“U” for unity) with the knob fully
DOWNRAMPINGTOD"OFGAINFULLYUP
4HROUGHTHEbMONOINPUTTHEREISD"OF
attenuation fully down and 30 dB of gain fully up,
with a “U” (unity gain) mark at 12:00. This 20 dB of
attenuation can be very handy when inserting a very
hot signal, need to add a lot of EQ boost, or both.
Without this “virtual pad,” this scenario might lead
to channel clipping.
MID
2.5kHz
MID
2.5kHz
MID
2.5kHz
MID
2.5kHz
MID
2.5kHz
80Hz
LOW
U
+15
-15
U
+15
-15
U
+15
-15
R
L
LOW CUT
100 Hz
U
GAIN
MI
C GAIN
U
+50
-20dB
+30dB
4
12kHz
HI
MID
2.5kHz
80Hz
LOW
U
+15
-15
U
+15
-15
U
+15
-15
12kHz
HI
MID
2.5kHz
80Hz
LOW
U
+15
-15
U
+15
-15
U
+15
-15
12kHz
HI
MID
2.5kHz
80Hz
LOW
U
+15
-15
U
+15
-15
U
+15
-15
12kHz
HI
PAN
AUX
U
+15
O
O
MON
FX
U
+15
O
O
R
L
PAN
AUX
U
+15
O
O
MON
FX
U
+15
O
O
R
L
PAN
AUX
U
+15
O
O
MON
FX
U
+15
O
O
R
L
PAN
AUX
U
+15
O
O
MON
FX
U
+15
O
O
80Hz
LOW
U
+15
-15
U
+15
-15
U
+15
-15
R
L
LOW CUT
100 Hz
12kHz
HI
PAN
AUX
U
+15
O
O
MON
FX
U
+15
O
O
80Hz
LOW
U
+15
-15
U
+15
-15
U
+15
-15
R
L
LOW CUT
100 Hz
GAIN
7/8
5/6
12kHz
HI
PAN
AUX
U
+15
O
O
MON
FX
U
+15
O
O
80Hz
LOW
U
+15
-15
U
+15
-15
U
+15
-15
R
L
MI
C GAIN
U
+50
GAIN
MI
C GAIN
U
+50
9/10
12kHz
HI
LEVEL
SET
LEVEL
SET
LEVEL
SET
LOW CUT
100 Hz
U
GAIN
MI
C GAIN
U
+50
-20dB
+30dB
LEVEL
SET
LEVEL
SET
LEVEL
SET
LOW CUT
100 Hz
U
GAIN
MI
C GAIN
U
+50
-20dB
+30dB
LOW CUT
100 Hz
U
GAIN
MI
C GAIN
U
+50
-20dB
+30dB
PAN
AUX
U
+15
O
O
MON
FX
U
+15
O
O
GAIN
80Hz
LOW
U
+15
-15
U
+15
-15
U
+15
-15
U
+20
-20
GAIN
U
+20
-20
R
L
11/12
EQ
EQ
EQ
EQ
EQ
EQ
EQ
EQ
12kHz
HI
PAN
AUX
U
+15
O
O
MON
FX
U
+15
O
O
dB
30
20
10
10
O
O
40
50
5
5
U
60
dB
30
20
10
10
O
O
40
50
5
5
U
60
dB
30
20
10
10
O
O
40
50
5
5
U
60
dB
30
20
10
10
O
O
40
50
5
5
U
60
dB
30
20
10
10
O
O
40
50
5
5
U
60
dB
30
20
10
10
O
O
40
50
5
5
U
60
dB
30
20
10
10
O
O
40
50
5
5
U
60
dB
30
20
10
10
O
O
40
50
5
5
U
60
3
2
1
OL
OL
OL
OL
OL
OL
OL
OL
MUTE
MUTE
MUTE
MUTE
MUTE
MUTE
MUTE
MUTE
19
20
21
22
23
24
25
26
27
28
29
30
GAIN
MI
C GAIN
U
+50
LEVEL
SET
GAIN
MI
C GAIN
U
+50
LEVEL
SET
GAIN
U
+20
-20