Mackie Onyx 32.4-Bus Owner's Manual - Page 16

ONYX 4•Bus 38. COMP ASSIGN 41. COMPRESSOR Meters 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 (depending 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 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 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 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 meters. 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 OO OO OO OO OO OO OO OO OO OO OO OO OO PREMIUM ANALOG MIXER w/ PERKINS EQ MATRIX A B GRP 1 -10 -20 0 MAX GRP 2 MAX MAX -30 +10 THRESHOLD 2:1 MAX 1.5:1 5:1 GRP 3 MAX GRP 4 MAX MAX OFF LIMIT RATIO MAIN GRP MIX 1-2 OFF GRP 3-4 MAX COMP ASSIGN MAX MAX LEFT MAX MAX RIGHT FAST ATTACK POWER LAMP 12V, 0.5A PHONES COMPRESSOR INPUT G.R. 0dB=0dBu 20 CLIP 1 15 2 10 3 6 4 3 5 0 6 2 7 4 8 7 9 10 10 20 12 30 15 MAIN MIX LEFT RIGHT CLIP 0dB=0dBu 20 15 10 6 3 LEVEL SET 0 2 4 7 10 20 30 BYPASS COMP PFL AFL RUDE SOLO +15 +15 MASTER STEREO AFL AFL OO MAX PHONES MAX MAX OO OO MONITOR SOLO LEVEL TB ASSIGN OO MAX MONO MAIN MAIN AUX AUX AUX OO MAX TO MON MIX 1-2 3-4 5-6 TALKBACK 16 ONYX 4•Bus