You're either looking at a mixer or thinking of buying one but either way you need to know exactly what it's for and how to use it. Few bits of band kit carry more mystique than the mixing desk - it comes with its own language and resembles the flight deck of a large airliner. Don't be put off by the jargon and the complexity, its really quite a simple beast once you've played around with it a little - and trial and error is the way that most of us come to terms with our mixers. Trial and error though can lead to costly errors and waste valuable time. I recently tried to record my band live but couldn't be both playing and on the desk, and only discovered afterwards that the engineer hadn't sent the signal to the DAW... All the complicated setting-up and checking was right but two and a half hours of live gig weren't captured at all because a simple matter of pressing one tiny button was overlooked - but... there you go, it's that easy to go wrong.
If you already have one, read this article with it in front of you. If you have yet to take the plunge, look up the one that interests you and check the specification, keep this handy while you read.
What is a Mixer?
A mixer, mixing console, mixing board or desk is a device that allows you to balance, position, effect and equalize various different audio channels into one sonic image - a mix. You can add FX to selected channels, position instruments to a location in the stereo field (pan), route channels to external FX units and shape the sound of each channel with a dedicated equalizer allowing you to adjust the bass, treble and mid range.
The first piece of 'band' kit we bought, as opposed to individual pieces of kit, was a Behringer mixer. Lots of venues have their own, as an integral part of the PA system, but many don't, or - if they do, they often turn out to be less than perfect - with channels that don't work, sticky faders, dodgy connections. The first gig we played, we found on setting up that the house mixer didn't work at all ie - no PA. We simply plugged in our trusty beast and left it to our own sound engineer to sort out. At other gigs it's proven a better desk than the resident one or it's mixed our stage sound for us. Inexpensive digital mixers, like ours, include microphone pre-amps, phantom power and the ability to record from the desk. It can be used to get tracks onto a home pc for DIY recording projects and a wide variety of loops, samples and FX that can be triggered live. Get one. Now. What follows will make a whole lot of sense if you are looking at a mixer - and hopefully much more sense than the manual does.
Why do we need a mixer?
Acoustic sounds - voices or musical instruments - are often collected through transducers - microphones and pick-ups. These produce weak electrical signals which must be amplified to line level. Amplification is performed by a pre-amplifier ("preamp"). At line level, signals can be more easily manipulated by devices such as mixing consoles and tape recorders. Manipulation at line level is what the mixer desk is for - it takes a number of signals (vocals, guitars, bass, drums etc) and allows you to balance and blend them into an audio mix, an output signal blended from all those inputs. Output signals are then sent to a power amplifier, where they are amplified to levels that can drive loudspeakers, which then convert the signals back into sounds that can be heard through the air. When you consider the variety of different sounds (vocal, percussive, electronic etc) and volume levels that a band produces, the need for a mixing desk to put it all together as a cohesive, balanced sound is easy to see.
Mixer Terminology
So, you're looking at the desk, a bewildering array of knobs and sliders with strange, alien names. Sound engineers excel at creating new names for otherwise familiar things and concepts - our sound engineer once stared blankly and uncomprehendingly at a question I raised about 'output leads' and after several minutes of this said cuttingly - "You mean 'feeds'. You should have said so". There were other words, mostly shortish ones denoting body parts and sundry related activities. Such are sound engineers. So, you're looking at the desk and you ask...
... What is a Channel?
A channel is an audio input that goes to a fader. A typical mixer channel will have an input selectorfor choosing mic (microphone) or line signals (such as a guitar output), a trim knobfor adjusting the input level (volume), and dedicated EQ(equalization) controls to alter the bass, midrange and treble bands of the signal (see above). A channel usually has sends which send part of the signal to an FX (effects) unit (or other destination). Finally a channel may have a bus selector switch which switches the channel output to a bus.
... What is a Fader?
A fader is a sliding level control that can be used to vary the loudness of any mixer channel. The name comes from "fading in" and "fading out" tracks. Look at your mixer - Is there a little "infinity"symbol at the bottom? Infinity means "zero" in mixer-speak. I did warn you about Sound Engineers' terminology... See the heavy line nextto the solobutton? That is the marker for 0dBvu, sometimes called the "nominal" or normal level. It signifies that at that point the signal that exitsthe fader is the sameas the signal that enteredthe fader. If you lowerthe fader from that point you attenuate(ie reduce) the signal. If you raisethe fader from that point you add gainto (or boost) the signal.
... And What's a Bus?
A bus is a faderwith its own dedicated output. You could also say that a bus is a major pathway from all channelsto a single faderconnected to an output. You can send everything going to that faderout of the mixer to another piece of gear - You can also bring the signal back in to the mixer on spare channels. Why would you want to do this? External FX processing for example - sending the signal for effects to be applied by an external unit then returning the processed signal so it can be sent on to a pa or other destination. On mixers with buses, there are routing buttonson each channel that lets you route the whole signal to one of the buses. The main busis often called the 'L/R bus'. Other buses are often grouped in pairs, like the 1-2 bus and 3-4 bus. There may also be another switch that lets you route these bus fadersto the 'master fader'. Typical uses of buses are to send a track (or groups of tracks) to a digital multi-track, or to a sound card or audio interface. Yet you can also be very creative with them, sending them to samplers, groove-boxes with analog inputs, surround encoders, separate compressors etc. Some buses may have channel inserts.
... Channel Inserts?
An insert is a pathway out and then back again into a single fader, letting you return the external signal to the mixer without using more channels. Use an insert to patch in an external piece of gear that only affects that one channel. Typical uses of inserts are patching compressors, outboard EQs, exciters, pedals, multi-track recorder input/outputs, and FX boxes. Lots of people route channel inserts to a patch-bay where they can plug in various devices conveniently. A well-featured mixer will have inserts on individual channels, busesand the master fader.
What is a Pan Pot?
Easy! A pan pot, is a little knob marked 'pan'... OK, you'll want to know what it is for - it is a panoramic potentiometer and it allows you to place the signal it applies to (see 'channel') anywhere in the stereo field, from extreme left to extreme right, and all stops in between. It helps you separate the sounds in the mix - very handy when you find yourself with flute, sax and harmonica playing guests.
What are the Mute/Solo buttons for?
The mute button silencesthe audio on a channel (so you can hear other stuff in the mix, from other channels). A solo button silences everything exceptthe signal on a channel so you can hear that channel in isolation. Our (un)sound engineer has been known to mute a channel not currently being used (lest someone inadvertently wreck his mix by coughing on a live mic or smacking a guitar into a mic stand. It's reasonable, but not when he goes off in search of more beer and the next song up requires that channel... be warned.
What are Routing Buttons?
Routing Buttons switch the audio signal down the pathway to the buses. Think of them as an output selector. If you press the '3-4' routing buttonand pan it (rotate it) all the way to the left / counter clockwise, the signal goes out by bus out 3. If you press the '1-2' routing button and pan it all the way right / clockwise, the signal only goes out bus 2. If you press 1-2, 3-4, and L-R and pan to the center point, the signal goes out through all 6 outputs. I recommend you try all these options just to know what the results are - we had our desk for 6 months before we realised how useful this could be.
What's a Send - and a Return?
A send is a major audio path that goes out of the mixer. There is, usually, a knob on each channel for each send so you can direct variable amounts of that channel to the pathway. These knobs send a variable amount, a little or a lot of each channel to a single mono output. A send can function as a separate monitor mix and is used forstage monitors. In a recording situation, the send typically goes to an FX unit. The signal is brought back to the mixerby the returns, and can be added to the main signal. A send is effectively a sub-mix. You don't have to bring back the sends to their returns. You can bring them back to an empty channel and continue to process with EQ, or on to a bus fader. You can use the returns like any other line input, patching in synths, other mixers, computer sound-cards, a CD player, decks and anything else you can think of.
Can you use a live console/mixer for recording to your DAW(digital audio workstation)?
Yes! Use the buses (now you know what they are) to get an isolated signal to your DAW, sound card, or audio interface. They all work the same way. Or use the inserts to connect to the DAW with unbalanced cables (see below and also your mixer manual will explain these). Shut off the global EQ. Things to look for - does the mixer have all the ins and outs you need? Does it have enough buses? Do you need direct outs? How many sends and returns, pre-amps, do you need? How is phantom power implemented? Are all the connections balanced (see below)? Which are not? This is a recording issue and beyond the scope of this article but any good home recording guide will give you the information you need. 90% of the digital mixers now available will do the job well - the size of the mixer, in terms of the number of inputs, is likely to be the variable factor but then - how many channels will you need to record at once?
How Big a Desk Do We Need for our Live Work?
The number of inputs is the key issue but note that 24 channels may only give you 12 analogue inputs and those are the ones you need for your mic's and any Dis (direct inputs). Bear in mind that if you are mic'ing drums that could involve 3 to 5 mic inputs or more. Behringer typically indicate the specification of the mixer in the model name - for example the Xenyx 2222 has a USB interface (that's the Xenyx bit), 22 channels, 2 buses and 2 master outs. The 2442 has 24 channels, 4 buses and 2 master outs. The former gives you 10 analogue inputs, the latter 12. Not all manufacturers use such descriptive model names however so be sure to read the specification data first.
Balanced and Unbalanced Cables
The XLR (mic') lead is balanced, similarly speaker leaders, and the guitar/instrument lead is unbalanced. Three wire system, balanced, and two wire system, unbalanced. In the balanced lead the positive and the negative don't contact the earth whereas in the unbalanced lead the negative and the earth are one and the same thing. The earth - (ground) is exactly that. The green earth wire goes to a copper stake in the ground so that any short circuit between the positive and earth will send the current to ground, but because the positive and the negative don't contact the earth it is said to be floating 'above ground'. The shield acts as a protection from interference by sending any extraneous electrical interference like hum, to ground. Unfortunately in the unbalanced circuit negative is ground! This makes your choice of stage box (multi-core cable) important as good ones feature a built-in 'ground-lift' that cancels that irritating hum which can drive sound engineers to distraction - and beers.
Unbalanced
The two signals of an unbalanced connection are referred to as "signal" and "ground". The ground is the zero reference while the signal has a voltage level that is above or below zero. This voltage level determines whether the signal is a 1 or a 0 (VGA, Audio & Video are Analog signals, the analog signal can have a voltage level anywhere between the high and low voltage levels). Coax cabling reduces exposure to cross-talk.
Balanced
Balanced signals are often called "current loop" signals and travel on "twisted pairs" (UTP for Unshielded
Twisted Pair or STP for Shielded Twisted Pair). The two signals in a balanced pair are like opposite charges of each other. What that means is if one wire has 12 volts, the other wire will have -12 volts. As the signal travels the pair, one wire radiates a magnetic field but as its partner wire generates an opposite field, the two fields cancel out. This cancelling is how balanced signals eliminate 'cross-talk'. Since Twisted pair wire is usually cheaper then Coax wire, balanced signals are more popular. Make sure that you have the appropriate cables and always have back-up. As with so many things in your live set-up, the cheap buy often turns out to be the most expensive over a period of time but a misplaced boot can swiftly kill the best shielded cable.
Your mixer can make a huge difference to your band's on-stage sound and getting to grips with it will teach you a lot about sound engineering and how to get the best out of your kit. It can also lead you into the fascinating world of recording - and be a huge help in writing and developing your own songs. Along the way you can discover the fun to be had with samples and other ways to enhance your live sound. Good luck!
