Mackie onyx 4-Bus Owner's Manual page 16

38. COMP ASSIGN
Use this switch to assign the compressor to either the
MAIN MIX, GROUP 1-2, GROUP 3-4, or OFF (not assigned).
When the compressor is assigned to the MAIN MIX, it
is inserted in the signal flow after the MAIN MIX fader,
so it works as an external dynamics processor. Once the
signal crosses the THRESHOLD, boosting the MAIN MIX
fader results in little change in the output level (de-
pending on the RATIO setting).
When the compressor is assigned to one of the GROUP
pairs, it is inserted in the signal flow before the GROUP
faders. In this way, the compressor can act on a group of
channels assigned to the subgroup (for example, drum
microphones), and the overall level of the compressed
group can be mixed into the main mix.
39. FAST ATTACK
The ATTACK setting determines how fast the com-
pressor reacts once the threshold has been exceeded. It
also affects the release time, which determines how fast
the compressor turns off once the signal falls below the
threshold.
With the switch up, the attack and release times are
calibrated to respond to the overall signal level without
the audible "pumping" and "breathing" artifacts that are
sometimes associated with compressors. In
most cases, this is the setting you would use
for live sound and recording applications.
There may be some situtations that
require a faster acting attack and release.
For example, mic'ing a snare drum produces
some fast transient peaks that may get
through the compressor before it can act
on the signal. Pushing in the FAST ATTACK
switch allows the compressor to react much
faster on quick transient peaks and release
the compression quickly between the peaks.
You can experiment with both settings to
determine which one works best in your
application.
40. BYPASS COMP Switch
When the BYPASS COMP switch is pushed
in, the signal bypasses the compressor, but
still allows you to see the input signal level
to the compressor and the amount of gain
reduction applied to the signal on the me-
ters. This is useful when setting up the com-
pressor settings prior to actually engaging
the compressor in a live sound application,
and for making A/B comparisons between
the compressed and uncompressed sound.
16
ONYX 4•Bus
41. COMPRESSOR Meters
The INPUT meter indicates the signal level at the
input of the compressor. Use this to help determine the
setting of the THRESHOLD control. Once the input level
crosses the threshold setting, the G.R. (Gain Reduction)
meters begin to light (top to bottom), as they indicate
how much gain reduction is being applied to the signal.
Note: If the COMP ASSIGN switch [38] is OFF, the
COMPRESSOR meters will not indicate any signal.
42. LEFT/RIGHT Level Meters
The Onyx 4•Bus Left and Right Level meters are
made up of two columns of twelve LEDs, with three
colors to indicate different ranges of signal level, traffic
light style. They range from –30 at the bottom, to 0 in
the middle, to +20 (CLIP) at the top.
The 0 LED in the middle is labeled 0 dB = 0 dBu.
You may already be an expert at the
world of "+4" (+4 dBu=1.23 V) and
"–10" (–10 dBV=0.32 V) operating
levels. What makes a mixer one or
the other is the relative 0 dB VU (or
0 VU) chosen for the meters. A "+4"
mixer, with +4 dBu pouring out the back will actually
read 0 VU on its meters. A "–10" mixer, with a –10 dBV
P R E M I U M A N A L O G M I X E R
w / P E R K I N S E Q
MATRIX
A B
-10
GRP
-20
1
-30
MAX MAX
O O O O
THRESHOLD
GRP
2 2:1
1.5:1
MAX MAX
O O O O
GRP
OFF
3
RATIO
MAX MAX
O O O O
GRP
4
MAX MAX
O O O O
COMP
ASSIGN
MAX MAX
O O O O
LEFT
FAST
ATTACK
MAX MAX
O O O O
RIGHT
MAX
O O
+15 +15
O O O O
PHONES
MASTER
STEREO
MAIN
AFL AFL TO MON
POWER
LAMP
12V, 0.5A
COMPRESSOR MAIN MIX
INPUT G.R. LEFT
0dB=0dBu
0
20 1
CLIP
CLIP
15 2
+10
3
10
6 4
3 5
5:1
LEVEL
0 6
SET
LIMIT
2 7
4 8
7 9
10 10
20 12
30 15
BYPASS
COMP
MAX MAX
O O O O
MONITOR
SOLO LEVEL
TB ASSIGN
MAIN AUX AUX AUX
MIX 1-2 3-4 5-6
PHONES
RIGHT
0dB=0dBu
20
15
10
6
3
0
2
4
7
10
20
30
PFL AFL
RUDE
SOLO
MAX
O O
MONO
MAX
O O
TALKBACK