Mackie ONYX 4Bus 38. COMP ASSIGN, 39. FAST ATTACK, 42. LEFT/RIGHT Level Meters, 40. BYPASS COMP Switch, 41. COMPRESSOR Meters

38. COMP ASSIGN 41. COMPRESSOR Meters

ONYX 4•Bus

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 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 ATTACK setting determines how fast the compressor 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.

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

There may be some situtations that require a faster acting attack and release. For example, mic’ing a snare drum produces

PREMIUM ANALOG MIXER w / P E R K I N S E Q

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LAMP	PHONES
12V, 0.5A

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

A	MATRIX		B
	GRP
	1
OO	MAX	OO	MAX
	GRP
	2
OO	MAX	OO	MAX
	GRP
	3
OO	MAX	OO	MAX
	GRP
	4
OO	MAX	OO	MAX

-10

-200

-30 +10

THRESHOLD

2:1

1.5 5:1

OFF LIMIT

RATIO

MAIN	GRP
MIX	1-2
OFF	GRP
	3-4

COMP

ASSIGN

COMPRESSOR			MAIN MIX
INPUT		G.R.	LEFT	RIGHT
0dB=0dBu			0dB=0dBu
20	CLIP	1	CLIP	20
15		2		15
10		3		10
6		4		6
3		5		3
0		6	LEVEL	0
			SET
2		7		2
4		8		4
7		9		7
10		10		10
20		12		20
30		15		30

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 compressor settings prior to actually engaging the compressor in a live sound application, and for making A/B comparisons between the compressed and uncompressed sound.

OO MAX OO MAX PFL AFL

	LEFT								RUDE
				FAST		BYPASS			SOLO
				ATTACK		COMP
OO	MAX	OO	MAX
	RIGHT
OO	+15	OO	+15	OO MAX	OO	MAX	OO	MAX	OO MAX
				PHONES	MONITOR		SOLO LEVEL		MONO
	MASTER
						TB ASSIGN
	STEREO
				MAIN	MAIN	AUX	AUX	AUX	OO MAX
AFL		AFL		TO MON	MIX	1-2	3-4	5-6	TALKBACK

16 ONYX 4•Bus