Top panel features, Channel controls, U. 4 20 4-channel line mix er – MACKIE U.420 User Manual
Page 12: Level set led, Instrument switch, Gain, U.420 4-channel line mixer
12
U.420 4-Channel Line Mixer
U.
4
20 4-Channel Line Mix
er
Top Panel Features
Channel Controls
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 LEDs are 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 passages might be lost in background noise.
11. INSTRUMENT SWITCH
When this switch is pressed in, channel 1’s left input
can accept direct instrument-level signals from guitars
or other instruments. They will be impedance-matched
to the channel 1 left input, without the need for a DI
box. (The right input is disconnected.)
When this switch is out, input 1 is a line-level input,
just like inputs 2–4. You can connect stereo line-level
sources such as CD players, MP3 players, keyboards,
drum machines, and tape players. You will need a DI
box if connecting instrument-level signals to the inputs
when this switch is out.
12. GAIN
These knobs allow you to adjust the gain of each
channel’s stereo preamplifier.
Signals from the line-level input jacks go straight
to the preamplifiers. Phono-level signals entering the
phono inputs [3] of channel 4 are first passed through
an RIAA phono preamplifier to become line-level signals.
The gain ranges from –14 dB to +14 dB, and the
center U position represents unity, or zero gain. Adjust
the gain 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 LED is on for about half the
time during your performance. Listen for any distortion
at the higher levels.
Adjust the gain after plugging in any input, or playing
a new source or instrument for the first time.
O
O
MAX
+14
-14
+14
-14
+14
-14
+14
-14
MID
LOW
HIGH
EQ
GAIN
LEVEL
U
U
U
U
U
U
U
U
U
O
O
MAX
1
2
3
4
U
O
O
MAX
LEVEL
U
O
O
MAX
U
U
MID
LOW
HIGH
EQ
GAIN
+10
KILL
U
+10
KILL
U
U
U
+10
KILL
U
+10
KILL
U
+10
KILL
U
+10
KILL
+10
KILL
+10
KILL
+10
KILL
+10
KILL
+10
KILL
+10
KILL
LEVEL
SET
LEVEL
SET
AUX
O
O
MAX
O
O
MAX
AUX
O
O
MAX
O
O
MAX
OL
10
7
4
0
4
10
20
POWER
L
R
MAX
FW IN
MAX
O
O
O
O
MAX
PHONES
O
O
LOOP
OUT