Mono Channel Strips
The Onyx24·4 has 20 mono channel strips and two stereo channels, and the Onyx32·4 has 28 mono channel strips and two stereo channels. Each mono channel has a mic and line input connector and an insert jack for connecting an external signal processor.
1. PAD Switch
In most cases, you will leave the PAD switch out. However, you may have a microphone that produces a higher output signal than usual, which may require you to turn the GAIN control way down. If that is the case, push in the PAD switch to insert a 20㏈ pad at the input to the mic preamp, to prevent overloading the microphone preamp and provide better gain control.
2. Low-Cut Switch
The Low-Cut switch, often referred to as a high-pass filter, cuts bass frequencies below 100㎐ at a rate of 18㏈ per octave.
We recommend that you use the Low-Cut switch on every microphone application except kick drum, bass guitar, bassy synth patches, or recordings of earthquakes. These aside, there isn't much down there that you want to hear, and filtering it out makes the low stuff you do want much more crisp and tasty. Now only that, but the Low-Cut switch can help reduce the possibility of feedback in live situations and it helps to conserve amplifier power.
Another way to use the Low-Cut switch is in combination with the LOW EQ on vocals during live performances. Many times, bass shelving EQ can really benefit voices. Trouble is adding LOW EQ also boosts stage rumble, mic handling clunks, and breath pops. Low Cut removers all those problems so you can add LOW EQ without losing a woofer.
Here’s what the combination of LOW EQ and Low Cut looks like in terms of frequency curves.
3. 48V Phantom Power Switch
Most professional condenser microphones require phantom power, which is a low-current DC voltage delivered to the microphone on pins 2 and 3 of the XLR microphone connector. Push in the 48V switch if your microphone needs phantom power. An LED light just above the switch to indicate that phantom power is active on that channel.
Dynamic microphones, like Shure’s SM57 and SM58, do not require phantom power. However, phantom power will not harm most dynamic microphones should you accidentally plug one in while the phantom power is turned on. Be careful with older ribbon microphones. Check the manual for your microphone to find out for sure whether or not phantom power can damage it.
Note: Be sure the MAIN MIX fader [72] is turned down when connecting microphones to the MIC Inputs, expecially when phantom power is turned on, to prevent pops form getting through to the speakers.
4. GAIN Control
If you haven’t already, please read “Set the Levels” on page 5.
The GAIN control adjusts the input sensitivity of the mic and line inputs. This allows the signal from the outside world to be adjusted to optimal internal operating levels.
If the signal is plugged into the XLR jack, there is 0㏈ of gain (unity gain) with the knob turned all the way down, ramping up to 60㏈ of gain fully up (-20㏈ to +40㏈ with the PAD switch pushed in).
When connected to the 1/4＂jack, there is 20㏈ of attenuation all the way down, and 40㏈ of gain fully up, with a “U” (unity gain) mark at about 10:00.
5. HIGH EQ
This control gives you up to 15㏈ boost or cut at 12㎑, and is flat at the center detent. Use it to add sizzle to cymbals, and an overall sense of transparency or edge to the keyboards, vocals, guitar, and bacon frying. Turn it down a little to reduce sibilance, or to hide tape hiss.
6. HIGH MID EQ
Short for “midrange”, this knob provides 15㏈ of boost or cut centered at the frequency determined by its FREQ knob (see HIGH MID FREQ next). Midrange EQ is often thought of as the most dynamic because the frequencies that define any particular sound are almost always found in this range. The HIGH MID EQ range (400㎐ to 8㎑) includes the female vocal range as well as the fundamentals and harmonics for many instruments.
7. HIGH MID FREQ
This knob ranges from 400㎐ to 8㎑ and determines the center frequency for the HIGH MID EQ filter. This allows you to zero in on the precise narrow band of frequencies you want to have affected by the HIGH MID EQ.
8. Low MID EQ
This is a second midrange EQ control that provides 15㏈ of boost or cut centered at the frequency determined by its FREQ knob. It extends down to 100㎐, which includes the male vocal range and the fundamentals of some lower instruments (guitar, lower brass).
9. LOW MID FREQ
This knob ranges from 100㎐ to 2㎑ and determines the center frequency for the LOW MID EQ filter. This allows you to zero in on the precise narrow band of frequencies you want to have affected by the LOW MID EQ.
10. LOW EQ
This control gives you up to 15㏈ of boost or cut at 80㎐. The circuit is flat (no boost or cut) at the center detent position. This frequency represents the punch in bass drums, bass guitar, fat synth patches, and some really serious male singers.
Note: Used in conjunction with the Low Cut switch, you can boost the LOW EQ without injecting tons of infrasonic debris into the mix.
11. EQ IN/OUT Switch
This is a true hardware bypass of the Perkins EQ circuitry to insure that there is no coloration of the signal if the EQ is not needed. When this button is out, the EQ controls to make an A/B comparison between the EQ’d signal and the signal without EQ.
[A Closer Look]
We have completely redesigned the EQ circuits in the Onyx Series of mixers, based on the designs of Cal Perkins, an industry-leader in audio engineering for over three decades and long-time Mackie collaborator. This “neo-classic” design provides the sweet musicality of the British EQ sound, while still maintaining 15㏈ of boost and cut with optimum Q and minimum phase shift(in other words, it gives you plenty of control and is pleasing to the ear!).
The 4-band equalization has LOW shelving at 80㎐, LOW MID peaking, sweepable from 100㎐ to 2㎑ on the mono channels, HIGH MID peaking, sweepable from 400㎐ to 8㎑ on the mono channels, and HIGH shelving at 12㎑. “Shelving” means that the circuitry boosts or cuts all frequencies past the specified frequency. For example, rotating the LOW EQ knob 15㏈ to the right boosts bass frequencies below 80㎐ and continuing on down to the lowest note you ever heard. “Peaking” means that the frequencies around the center frequency are less affected by the EQ the further away they are.
12. AUX Sends
These tap a portion of each channel’s signal (pre or post-fader) out to either an effects processor (post-fader) or for stage monitoring (pre-fader). The AUX Send levels are controlled by the channel’s AUX 1-6 knobs, and by the AUX SEND MASTERS knobs [55].
These are more than just effects and monitor sends. They can be used to create stereo in-ear monitor mixes, generate separate mixes for recording, for another zone, or “mix-minuses” for broadcast.
13. PAN
PAN adjusts the amount of channel signal sent to the left versus the right outputs.
With the PAN knob hard left, the signal feeds the MAIN LEFT (and GROUP 1 and 3, depending on the setting of the GROUP ASSIGN switches). With the knob hard right, the signal feeds the MAIN RIGHT (and GROUP 2 and 4)
The Onyx4·Bus PAN control employs a design called “Constant Loudness.” If you have a channel panned hard left (or right) and then pan to the center, the signal is attenuated 3㏈ to maintain the same apparent loudness. Otherwise, it would make the sound appear much louder when panned center.
14. MUTE
Press this switch to mute the individual channel. This disconnects the channel’s signal from all the Groups, the Main Mix, and Aux Send buses (pre and post-fader). You can still solo the channel (PFL) when the MUTE switch is pushed in.
15. Channel Fader
The fader controls the channel’s level… from off to unity gain at the “U” marking, on up to 10㏈ of additional gain.
Mackie mixers have a “U” symbol on many of the level controls. This “U” stands for “unity gain,” meaning no change in signal level. Once you have adjusted the input signal to line-level, you can set the controls at “U” and your signals will travel through the mixer at optimal levels. What’s more, many of the labels on our level controls are measured in decibels (㏈), so you’ll know what you’re doing level-wise if you choose to change a control’s settings.
16. Siganl Level LEDs
These LEDs indicate the channel’s signal level after the GAIN and EQ controls, but just prior to the channel’s fader. So even if the fader is turned down, you can see if a signal is present.
If you’ve followed the “Set the Levels” procedure, the –20 and 0 LEDs should light frequently, the +10 LED should light occasionally, and the OL (Overload) LED should not light at all. If the OL LED is blinking frequently, the signal is probably distorted from overdriving the input. Either turn down the GAIN control or turn down the signal at its source.
17. GROUP and MAIN MIX ASSIGN Switches
Alongside each channel fader are three buttons referred to as channel assignment switches. Used in conjunction with the channel’s PAN knob, they are used to determine the destination of the channel’s signal.
With the PAN knob [13] at the center detent, the left and right receive equal signal levels (GROUP 1-2, 3-4 and MAIN MIX L-R). To feed only one side or the other, turn the PAN knob accordingly.
If you’re doing a mixdown to a 2-track, for example, simply engage the MAIN MIX switch on each channel that you want to hear, and they’ll be sent to the MAIN MIX bus. If you want to create a subgroup of certain channels, engage either the 1-2 or 3-4 switches instead of the MAIN MIX, and they’ll be sent to the appropriate Group faders. From there, the groups can be sent back to the MAIN MIX (using the MAIN MIX assign switches [70] next to the Group faders), allowing you to use the Group faders as a master control for those channels.
If you’re creating new tracks or bouncing existing ones, you’ll also use the GROUP ASSIGN switches, but not the MAIN MIX switch. Here, you don’t want the subgroups sent back into the MAIN MIX bus, but sent out, via the GROUP OUTS jacks [85], to your multitrack inputs. However, if you’re printing tracks via the DIRECT OUTS [76], the channel assignment switches don’t matter because the DIRECT OUTS come before the ASSIGN switches.
18. PFL SOLO Switch
This handy switch allows you to hear signals through your headphones or monitor outputs without having to route them to the MAIN or GROUP mixes. Folks use solo in live work to preview channels before they are let into the mix, or just to check out what a particular channel is up to anytime during a session. You can solo as many channels at a time as you like. It won’t affect what is coming out the MAIN OUT or GROUP OUT jacks.
The Onyx4·Bus has two solo modes. PFL (Pre-Fader Listen) is the default solo mode, and the mode used for inputs, including soloing individual channels and the Stereo Returns. AFL (After-Fader Listen) is activated whenever an AFL switch is pressed on an output, including an Aux Send, Matrix, or Group.
PFL solo mode always overrides any AFL solo mode. The Rude Solo LEDS [43] below the SOLO meters indicate which solo mode is active.
Soloed channels are sent to the PHONES output and MONITOR outputs, and also to the MAIN MIX meters. PFL mode sends the channel’s siganl after the GAIN and EQ controls, but before the channel fader, to the PFL solo bus (and appears on the LEFT meter). AFL mode, sends the signal post-fader (and appears on the LEFT and RIGHT meters), making it ideal for mixdown soloing.
VERY IMPORTANT: Remember, PFL mode taps the channel signal before the fader. If you have a channel’s fader set way below “U”, PFL solo won’t know that and will send a unity gain signal to the MONITOR OUT and PHONES output. That may result in a startling level boost at these outputs when switching to PFL solo mode.
