Top panel features, Channel 1 and 2 controls, U. 4 20d 4-channel mic/line mix er – MACKIE U.40d User Manual
Page 14: Level set led, Instrument switch, Gain, U.420d 4-channel mic/line mixer
14
U.420d 4-Channel Mic/Line Mixer
U.
4
20d 4-Channel Mic/Line Mix
er
Top Panel Features
Channel 1 and 2 controls
Channel 1 and 2 are mono channels, fed by the combo
input connectors [1]. The controls are mono, but the
final output of each channel is split equally and added
to the left and right main mix.
10. LEVEL SET LED
These LEDs are used with the gain control [12] to set
the level of the channel’s preamplifier gain just right.
They light when the signal level is 0 dBu.
Adjust the gain control so these LEDs come on while
you are playing, and go off when you stop. As a rough
guide, adjust the gain until the LED is on for about half
the time during your performance.
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 your quieter, exquisitely-
delicate performance might be lost in background noise.
11. INSTRUMENT SWITCH
When this is pressed in, channel 1’s 1/4" TRS input
can accept direct instrument-level signals from guitars
or other instruments. They will be impedance-matched
to the channel 1 input, without the need for a DI box.
When this switch is out, input 1 is just like input 2,
and you will need a DI box if connecting instrument-
level signals to the inputs.
12. GAIN
This knob adjusts the gain of the preamp for any mi-
crophone or line-level source you care to plug into the
input jacks [1].
The gain ranges from +3 dB to +50 dB of gain for
microphone-level signals coming in on the XLR inputs,
and from –22 dB to +25 dB for line-level signals coming
in on the 1/4" TRS inputs. Adjust the gain control so the
level set LEDs [10] come on while you are playing, and
go off when you stop. As a rough guide, adjust the gain
until the LEDs are on for about half the time during
your performance. This gives you the best signal-to-
noise ratio for the preamp.
Adjust the gain after plugging in any input, or playing
a new source or instrument for the first time.
GAIN
U
HIGH
EQ
+10
KILL
U
U
U
+10
KILL
MID
U
+10
KILL
U
+10
KILL
LOW
U
+10
KILL
U
U
U
+10
KILL
+14
-14
+14
-14
MID
MID
FREQ
HIGH
12kHz
LOW
80Hz
EQ
AUX
AUX
+50
+3
O
O
+15
-15
U
MAX
O
O
MAX
8k
100
600
+15
-15
U
+15
-15
U
+15
-15
U
+15
-15
U
+15
-15
U
+25
-22
MIC
+50
+3
+25
-22
MIC
150
1.5k
8k
100
600
150
1.5k
CURVE
GAIN
1
2
3
4
3
4
O
O
-20
-10
+10
-5
0
5
O
O
MAX
O
O
MAX
LEVEL
O
O
MAX
O
O
MAX
LEVEL
SET
LEVEL
SET
SLOW
FAST
OL
10
7
4
0
4
10
20
POWER
48V
L
R
MAX
FW IN
MAX
O
O
O
O
MAX
PHONES
O
O
CUE
LOOP
OUT
CUE
CUE
CUE
CUE
48V