Gain; Level Set Led; Low Cut - Mackie ProFX12 Owner's Manual

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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
U
LEVEL
mono line input), the gain knob adjusts
SET
the input sensitivity of the mic and line
U +50 -20 +20
inputs.
GAIN GAIN
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
down, ramping to 50 dB of gain fully up.
Through the 1⁄4" mono input, there is 20 dB 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.
18
ProFX8 and ProFX12
LINE/HI-Z IN 1 LINE IN 2 LINE IN 3
20
INSERT INSERT INSERT
U U U
LEVEL LEVEL
SET SET
U +50 U +50 U +50
21 +30dB +30dB +30dB
-20dB -20dB -20dB
GAIN GAIN GAIN

LOW CUT

LOW CUT LOW CUT
100 Hz 100 Hz 100 Hz
EQ EQ
U U U
HI HI
12kHz 12kHz
-15 +15 -15 +15 -15 +15
U U U
MID MID
2.5kHz 2.5kHz
-15 +15 -15 +15 -15 +15
U U U
LOW LOW
80Hz 80Hz
-15 +15 -15 +15 -15 +15
AUX AUX AUX
U U U
MON MON
+15 +15 +15
O O O O O O
U U U
FX FX
+15 +15 +15
O O O O O O
PAN PAN PAN
L R L R L R
MUTE MUTE MUTE
29
OL OL OL
1 2
dB dB dB
10 10 10
5 5 5
U U U
5 5 5
10 10 10
20 20 20
30 30 30
40 40 40
50 50 50
60 60 60
O O O O O O
LINE IN 4 LINE IN 5 LINE IN 7
UNBAL
R
INSERT LINE IN 6 LINE IN 8
U
LEVEL LEVEL LEVEL
SET SET SET
U +50
U +50 U +50
+30dB
-20dB
GAIN GAIN GAIN
LOW CUT LOW CUT LOW CUT
100 Hz 100 Hz 100 Hz
EQ EQ EQ
U U U
HI HI HI
12kHz 12kHz 12kHz
-15 +15 -15 +15 -15 +15
U U U
MID MID MID
2.5kHz 2.5kHz 2.5kHz
-15 +15 -15 +15 -15 +15
U U U
LOW LOW LOW
80Hz 80Hz 80Hz
-15 +15 -15 +15 -15 +15
AUX AUX
U U U
MON MON MON
+15 +15 +15
O O O O O O
U U U
FX FX FX
+15 +15 +15
O O O O O O
PAN PAN
L R L R L R
MUTE MUTE MUTE
OL OL OL
3 4 5/6
dB dB dB
10 10 10
5 5 5
U U U
5 5 5
10 10 10
20 20 20
30 30 30
40 40 40
50 50 50
60 60 60
O O O O O O
LEVEL
SET
U +50
GAIN
U
LEVEL
SET
U +50 -20 +20
GAIN GAIN

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
that cuts the bass frequencies below 100 Hz, at a rate of
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.
LINE IN 9 LINE IN 11
UNBAL UNBAL UNBAL
R R R
LINE IN 10 LINE IN 12 ST RETURN
U U
LEVEL
SET
15
10
-20 +20 -20 +20
5
GAIN GAIN
0
5
EQ EQ EQ
U U
10
15
HI HI HI
12kHz 12kHz 12kHz
125
-15 +15 -15 +15
U U
MID MID MID
2.5kHz 2.5kHz 2.5kHz
-15 +15 -15 +15
U U
LOW LOW LOW FX PRESETS
80Hz 80Hz 80Hz
01 BRIGHT ROOM
02 WARM LOUNGE
-15 +15 -15 +15
03 SMALL STAGE
04 WARM THEATER
AUX AUX AUX
U U
05 WARM HALL
06 CONCERT HALL
07 PLATE REVERB
MON MON MON
08 CATHEDRAL
09 CHORUS
+15 +15
O O O O 10 CHORUS + REV
U U
11 DOUBLER
12 TAPE SLAP
13 DELAY 1 (300ms)
FX FX FX
14 DELAY 2 (380ms)
15 DELAY 3 (480ms)
+15 +15 16 REVERB + DLY (250ms)
O O O O
PAN PAN PAN
U
+15
L R L R O O
FX MASTER
MUTE MUTE MUTE
OL OL OL
7/8 9/10 11/12 ST RTN
dB dB dB
10 10 10
5 5 5
U U U
5 5 5
10 10 10
20 20 20
30 30 30
40 40 40
50 50 50
60 60 60
O O O O O O
For hybrid channels (mic input and U
stereo line input), the gain control just
affects the microphone input.
-20 +20
GAIN
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.
MON SEND FOOTSWITCH
UNBAL UNBAL
BAL /
R R
UNBAL
FX SEND MAIN OUT PHONES
STEREO GRAPHIC EQ
15
48V
10
PHANTOM
5
POWER
0
5
POWER
10
MAIN
15
METERS
250 500 1K 2K 4K 8K
0dB=0dBu
OL
MAIN MIX EQ IN
15
MON BYPASS
10
6
3
USB
0
2
4
U
7
10
20
30
+10
O O
L
INPUT LEVEL
PRESETS
MUTE
USB THRU BREAK
(MUTES ALL CHANNELS)
U U
OL
+15
O O MAX +20
O O O O
FX TO MON PHONES TAPE LEVEL
MAIN
MON
FX RTN
dB dB dB
10 10 10
5 5 5
U U U
5 5 5
10 10 10
20 20 20
30 30 30
40 40 40
50 50 50
60 60 60
O O O O O O
R