Thinking of buying a mixer?

The place for general discussion of Cakewalk Pro Audio.

Thinking of buying a mixer?

Postby andychap » Tue May 02, 2006 4:00 pm

Mixers come in many forms, but they
basically all perform exactly the same task – they take a variety of different audio signals, blend them together and balance their volumes, process them with EQ and effects, and then output the finished product in a specified way for whatever you want to do with it.

Yet even in that relatively simple sentence, there are any number of variables that can alter the choice
of system that’s right for you. And then there’s the differences in the way they work, the formats, and the features.

It’s pretty safe to say, that for whatever mixing task you can think of, there are a couple of solutions
available – and we’re going to try to look at a good few of them here.

The essential differences between mixers is basically; the number of input channels, and the type of connections they offer, the presence of phantom power, the nature of the sound shaping capabilites (EQ), the number of busses and auxiliary channels, the routing and patching systems, and the number of output options – if that’s all gobbledygook, then; Read on McDuff...

There’s a fair amount of transportation related terminology to mixers – depicting the journey of the audio signal from one side to another. The major one of these is channel – the path (there we go again) that one of the given audio signals to be mixed takes. Channels are usually arranged vertically down the mixer, with the input at the top and the channel fader (long slidy thingy that sets the volume)
at the bottom. On the way from one to the other there are a range of detours, alterations and travel arrangements that can be made – but all mixers
adhere basically the this channel format.

Another term you’ll here plenty about is ‘bus’, which basically is a mass transit system for any audio signal that you want to assign to it. Let me
explain, bus' are additional outputs from the mixer additional to the master fader. You can assign an audio signal to ‘get on’ the bus of your choice,
which is routed to a specific audio output. This can be an effects bus, a record bus for routing to a multi-track, or a submix bus for a monitor mix.

Auxilliary bus’ are slightly different in that you can control the amount of the signal to be sent to them. Whereas output bus', or subgroups, or submixes are simply assigned and then controlled
by a fader. More is explained below. The vast majority of mixers adhere to this model – and use this terminology of the channel strip – and the order in which these features come is pretty
standard too. So here’s a general description of one based on a relatively standard analogue desk.

INPUTS

Analogue desk inputs are usually via three types of connection; XLR for mics, ¼” jacks for instruments
and RCA phono connections for stereo sources like tape/CD/Minidisk and turntable. Digital inputs are
another whole new world, and formats like ADAT, S/PDIF, mLan, R-Bus etc. are worthy of a new article in
themselves – so we’ll assume that if you use those formats, you have some knowledge of them and their requirements. Digital signal inputs, and digital mixers are unique in the flexibility of routing that they offer in terms of inputs and outputs, because
of the nature of their construction any signal can be routed anywhere.

For analogue users though it’s a choice of mic or line in depending on the signal source. The channels are invariably given a gain control, to boost the incoming signal to the optimum level (it’s usually
recommended that you set the fader to 0dB/Unity gain (the point where it neither boosts nor cuts the signal strength) employ the PFL (see below) and then attenuate the gain until it reaches the optimum level.

The dynamic mics generally used in live work do not require any external power – however many types of studio mics, and an increasing number of stage condenser mics available, do. This is generally
referred to a Phantom Power, and it is provided to the mic via its XLR lead from the pre-amp of the mixer. It is usually employed via a switch on the
desk, either to mic inputs individually, or globally to all mic – needing you to ensure that no unbalanced
lines are connected to XLR ins when you activate it.

Mic inputs may also be afforded a low cut filter on the input channel – to help combat any low frequency rumbling or proximity effect.

LINE LEVEL

Line in, or Line Level inputs for instruments such as keyboards, samplers or drum machines, can also be used to accept the returns from multitrack tape
machines and other recording media.
The insert point is used to add signal processing into the channel – effective on 100% of the signal (this is important later), these are traditionally applied for connecting dynamic effects like compression or gating via ¼” TRS jacks – where
the signal is sent and returned on one jack. However, there is no hard and fast rule as to how these insert points can be used.

FILTERS + EQ

EQ or Equalization, is effectively frequency conscious mixing... Allowing you to cut or boost specific
frequency ranges within a given audio signal. The most obvious example of this is a graphic EQ – they don’t call them that for nothing, you know – which
offers a pretty obvious visual explaination of the amount of cut/boost being applied to a specific frequency bands. Unfortunately, graphics take up a lot of space, if you want them to be as accurate as we’d often like. So a mixer employs different methods.

Less well spec’d desks will employ fixed EQ, where the designer will make a decision as to the frequency location that the EQ controls will be centred around.

These are denoted Low/Mid/High (some desks may offer Low-Mid and High-Mid) in basic systems. Also decided will be the Q, or the amount of signal either side of that frequency point that the control will effect.

Then all that’s left to be controlled is the amount of cut available to the mixer – usually the better the mixer, the more control you’ll have.

More advanced desk will offer parametric EQ – or at least a limited version of it. A Parametric EQ is
much like a synthesiser filter – as it relies on three controls; a cutoff frequency control (defining the centre point) – allowing you to tune the EQ to exactly the right area of the signal, a Q control for widening or narrowing the bandwidth which it will effect, and
a control for the amount of cut or boost. But, instead of a resonance control – which provides a small boost
around the cutoff point - a parametric EQ swaps the filters fixed slope for a variable control to designate the amount of cut/boost applied. Fully parametric EQs can sweep the entire frequency range of a mixer, but what’s more common is ‘swept’ EQ, whereby the
cutoff point of the Low/Mid/High frequency range can be moved within a limited area – offering plenty of flexible control. Some desks will offer a mixture of fixed and parametric EQ – with the more flexible type being located within the mids, where the most
accurate EQ is needed to get a good overall sound. These are often referred to as a ‘swept mid’ EQ.

AUXILIARY CHANNELS

Auxiliary sends are essentially extra output channels from the desk – that are married to corresponding auxiliary return channels (depending on the desk,
these will either appear as separate channel strips or more likely, rotary potentiometers in the master section). The main purpose of an auxiliary send is
to route the signal to effects processors, the results of which are then blended with the original signal
dependant on the setting of the send and return levels – the level of which is controlled by the pots. The more flexibility you need in your signal
processing, the more auxiliary sends you’re going to need. A secondary use in smaller mixers (which don’t have subgroups - explained below) is to create submixes – using the aux sends to control the levels – for output to monitors, or a recorder.

PFL

PFL or Pre-Fade Listen, sends a channel’s signal to the monitor bus prior to it being routed to the channel fader, this means you’re listening to the incoming signal, not the end result after the fader... good for monitoring input levels.

MUTE/SOLO

These switches usually sit below the EQ section near the channel fader. Mute does pretty much what it says and stops the channels signal being sent to the
master output fader, and the solo switch allows a signal to be routed to the monitor busses without being sent to the master bus. This allows track to be previewed before being bought into the mix, or to be monitored over headphones in isolation during a
live mix – great for troubleshooting.

ROUTING

In a similar area to the mute/solo buttons, on some mixers you will find further buttons for assignment of signals to subgroups, or output busses – they will be numbered switches corresponding to the number of subgroups allowed by your mixer. They are similar to auxiliary channels, but are afforded their own channel strip and EQ controls for their specific task.
In a studio, they would be used when the number of recording channels is limited, to sub-mix incoming signals down to the desired number (i.e. seven
incoming mixed being recorded down to four tracks available on the multi-track). In a live situation, if
subgroups are available they are often utilised to provide a monitor mixes to the stage. Or, simply to group various sets of instruments together, making
them controllable with one or two faders rather than a whole bunch – especially useful for multi-mic’d
instruments like drums. This is useful at mixdown too for making quick changes on the fly.

DJ mixers use routing like this to monitor records not in the mix, many will have a monitor switch for each channel, the pressing of which will route that channel’s signal to the headphone/booth outputs of the mixer, effectively a Pre-Crossfader Listen. Other more advanced DJ mixers will allow you to balance the levels of Master and Monitor signals in the
headphones too.

THE MASTER SECTION

The Master section of a mixer, is the main output bus. Usually dominated by twin-fader control and a metering system of some kind to visually monitor
output levels. This is where the all signals intended for the main stereo out are routed to during a mix. It will also be the home to the various other
outputs of a mixer, or at least their controls (the physical outs are positioned either be on top of the desk on smaller consoles, to the rear, or on a patchbay interface with some large consoles). These include the in/out jacks for the aux sends, and their
master output and return level faders – controlling the level of the aux outs and the amount coming back into the desk, monitor outputs and level
control, headphones socket and amplifier, and any final routing switches offering options for directing
subgroups to the main mix (though they may be located as part of the subgroup channel, depending on design).

So, the questions you need to ask yourself before whilst you’re planning a purchase should run a little
something like this;

So, you can see the audio signal can take a long and convoluted journey through a mixer, being EQ’d, submixed, sent through auxiliary channels to effects or submixes, subgrouped before eventually being routed back out either to amplifier, recorder, monitor
or headphones.

• What’s it for?
• Where am I going to use it?
• Is it going to be fixed in one place or portable?
• How many audio sources am I going to
need to connect?
• How many simultaneous mic channels
am I going to need?
• What kind of input/output formats and
connections do I need?
• What kind of processing does it need to perform – in terms of effects and EQ
• How much can I afford?
The three main areas of application for a mixer in music are in the studio, a live show, or for use by DJs. Though there are several sub-types of within each specialist discipline, their uses also crossover the genres – because, like we said earlier, all mixers
work essentially the same way – and using the ‘correct’ mixer for the job, is often as much an issue of convenience, not necessity. You see, most audio adheres to certain standards – analogue signals are usually described as mic, or line level signals; meaning the former needs pre-amplification in order to boost the signal for use in the mixer. Most mixers
can deal with both, but some with only one... such as some basic DJ mixers, only designed for use with the output of decks, that need pre-amplification. In
fact, in general DJ mixers can often be the simplest of the mixer layouts – because many time you will only be mixing two stereo sound sources (so the
mixer may only need four mono channels), the records are already EQ’d, so do not need advanced EQ – though some mixers do employ them, they
are generally done differently for DJ mixers. So decide in advance what you’re going to be recording, or playing back – if it’s lots of mics,
check the quality of a mixer’s pre-amps, you’ll also want filters and good EQ, Insert points and probably subgroups too.

SIZE IS EVERYTHING

The problem with choosing a mixer is always going to be capacity - how big does a mixer need to be? The more specific the task, the easier this is to come to a conclusion on – I mean, a two decks and a mixer guys, needs a DJ mixer right?

Simple. Yeah, but look ahead – are you going to want more channels, more instruments – better to buy big once. Then it’s the I/O considerations, are
you all analogue or a mix of the two? Whatever the format, does the mixer your looking at have all the right options, or will it be a compromise?

The big home studio choice these days is – of course – analogue vs. digital. Or even, in many cases whether to invest in a mixer at all, or to just
purchase a controller surface for a DAW system. A new development in mixers is the hybrid concept illustrated by systems like Yamaha’s 01x – part
controller, part soundcard, part pre-amp, connected to a computer by a digital mLan connection.

When system such as Cubase provide such
powerful EQ facilities, automated mixing, instant scene recall and all the other features that the computer interface can offer, one may wonder ‘why
bother with a mixer at all?’, and indeed many are. If you are rarely recording more than two or three
simultaneous sound source, then this is probably a good option for the PC/Mac based studio – if you are only recording single sources (vocals only for example), then a quality pre-amp would be an even better investment, unless hands-on mixing is what
you require.

Digital mixers/controllers like the 01x tend to offer much more than just mixing though – they virtually all include their own effects, dynamics
control – like compression and gating, EQ and great routing options due to their flexibility of internal
configurations – so those wanting to get more out of their computer by taking strain from the CPU, should
look this way perhaps... Behringer’s DDX3216, appearing to be the budget option of choice at the present time, with Yamaha’s O2R unit also being a
popular choice.

WE GET AROUND

Obviously, the portability of a mixer is important to anyone who wants to take one out on the road, these compromises to keep size down will effect not only flexibility, but ergonomics – a factor that many people don’t consider. It stands to reason
that the more channels you want, the bigger the mixer you’re going to need – and it also stands to reason that the smaller you want a mixer to be, the
more cramped all of the controls are going to be, or the more they are going to have to take away.

Many small notepad mixers like Spirit’s
Folio Notepad utilise rotary pots instead of the more accurate fader controls to save space – Studiomaster’s C1 being a notable exception. And the features set you’re offered is going to relate pretty much to what you’re willing to lug around with you the bigger the desk, the more features
you’re going to have and the easier it is going to be to use those features in the dark/under pressure – providing the mixer layout’s good in the first place.

Live applications also throw up a range of configuration options; with powered units available that integrate the mixer and the power amplifier – units like the IMG Stageline powered units or
the Allen&Heath PA range – which are styled like conventional desks. Another style for powered mixers is that of the new Wharfedale BX range. These units employ the mixer/amp approach as a
rackmount unit, ideal as a low-intensity portable PA for rehearsal spaces or gigs, but limited in their
routing and channel capacity. Units like these often also include internal effects to make up for this (these usually come in preset form, as a opposed to the greater flexibility of digital mixers whose LCD screens usually afford more editability)

Studio desks – certainly those for larger project studios – can afford to be a lot less concerned about space restrictions... Due to the obivious fact
that they don’t have to move. Of course this makes for some monster desks offering heaven-knows how many inputs and 48 busses for routing to the
recorder (all with their own channel strips), then the the auxiliary channels and what not. You’re talking
mega-bucks here, and most mere mortals will never get close to one, but they exist.

The important thing to remember is that mixers are simple, all perform the same function – just in very different ways. The best thing to do is to map out exactly what your input and output needs are – including bussing (be practical though), then make a
budgetary assessment of what you can afford, then start to look at the different options for that size of
desk for that amount of moolah. This will invariably point you to a ready-made solution.

The aesthetics of EQ and mic pres is for another day, but will also influence your decision – and the
rule is often ‘you get what you pay for’, in terms of quality, durability and ergonomics – but the gaps are closing, and these essentially simple items are getting more advanced and cheaper. Happy mixing!

Thanks to Music Mart UK for the info.
andychap
 
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Re: Thinking of buying a mixer?

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Postby jatkins » Sat May 15, 2010 3:29 pm

How do I access a manual equalization for my total mix before converting to a .wav file using Cakewalk Sonar>
jatkins
 
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