Building the Perfect PA System for You: Mixers

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Part 3: Choosing the Right Mixer for Your PA System

The mixer is the brain of a PA system. It is Grand Central Station. The entire purpose of a mixer is to take various feeds from different sources, mix them together, and route them to the appropriate destinations. While mixers are sold as complete units in most cases, they are still modular devices – that is, they are a collection of components meant to work together to complete a task. As such, there are hundreds upon hundreds of options available, each suited to a particular situation. While a live music venue may permanently install a large mixer with tons of functionality, the solo singer/guitarist has no need for such a beast of a machine.

So how can you tell which mixer would suit your needs? The key is to Know Thyself. More to the point, know your setup. We will get into typical situations and the features they call for later in this piece, but for now, let’s take a look at the essential components of a mixer.

Anatomy of a Mixer

Big mixers are especially daunting to the uninitiated, but it’s really not as complicated as it looks. That iconic bank of rows of knobs and sliders are really just a single set of controls, reproduced over and over again for each individual input.

Starting from the top, we have:

• The Input/Preamp – this is where you plug in. The ones with XLR inputs have preamps – a necessity for amplifying microphone signals. The TRS inputs are line level inputs for media players or line-level instruments like keyboards or synthesizers.
• Gain – This is where you adjust the level of the signal in the preamp as it goes into the mixer, before any routing or processing.
• EQ – This allows you to accentuate or attenuate key frequencies in order to address issues like feedback and mix integrity. The Input/Preamp – this is where you plug in. The ones with XLR inputs have preamps – a necessity for amplifying microphone signals. The TRS inputs are line level inputs for media players or line-level instruments like keyboards or synthesizers.
• Gain – This is where you adjust the level of the signal in the preamp as it goes into the mixer, before any routing or processing.
• Equalizer (EQ) – This allows you to accentuate or attenuate key frequencies in order to address issues like feedback and mix integrity.
• Aux/Sends – These allow you to send a signal to a secondary location in addition to the master channel. These are needed not only to send signals to the monitors, but to send signals to external effects. Any effects send must utilize a return channel. Some mixers feature dedicated return channels for FX loops, but any extra channel can function as a return.
• Pan – Allows you to decide the stereo placement of the particular channel’s signal.
• Volume Fader – Dictates the volume of the channel in the master channel. This is different from the gain control – and you will need to learn how to use the two level controls together in order to achieve optimal levels in your mix.

Different mixers provide different levels of control throughout, but those are the basic modules of a mixer. Some smaller economical mixers will even sacrifice these bare-bones features for the sake of portability or affordability.

Must-Have Features

So now that we know the elements of a mixer and what it is supposed to do, let’s look at some key features that, in my opinion, are MUST HAVES in your choice of a mixer. This is my bare-minimum recommendation for any situation.

Enough Preamps/Inputs/Channels

You need to be able to plug everything in. That means every microphone, every keyboard, and every electronic do-hickey you plan on using MUST have a channel (or two if a device needs a stereo input). This includes your media player for set break. Each microphone you plan to use must also have a channel with a preamp. Do not skimp here – your mixer will not get the job done if you do.

48V Phantom Power

Some microphones require power from the mixer in order to work. Often, these will be condenser microphones used for drum overheads, but you may come across others as well. This is also required for active DI boxes. You may be able to get away without it, but you will kick yourself when you need it. It’s pretty standard, so you shouldn’t have to do without it anyway.

Aux Sends

You need at least one send on your mixer in order to have a monitor mix. Solo performers may have an easier time working around this one, but in my opinion, this is still a must-have for any mixer. Even one send can be daisy-chained to as many monitor speakers as needed.

Nice-to-Have Features

Now that we know what we absolutely need from our mixer, let’s have a look at some features that aren’t dealbreakers if they are missing, but still very nice to have.

Extra Channels/Preamps/Sends

You never know when you may want to feature a guest at a performance. Perhaps your act may grow in the coming months, changing from solo performer to a small combo. Maybe your patron wants to plug in an extra microphone for the event’s emcee. There are tons of reasons to have a little more than you absolutely need, so if it’s doable, get a board that is slightly bigger than your situation calls for.

Stereo Channels / Dedicated Aux Inputs

Stereo channels are handy because they have one set of controls to govern a stereo pair of inputs. Aside from streamlining stereo instrument or effects controls, this type of channel is great to set aside for a media player. Some mixers even have dedicated RCA or 3.5 mm inputs for this precise reason.

USB output

Many modern mixers feature a duplicate master output via USB. This is perfect for recording sets or rehearsals for yourself or your fans. Some may also feature duplicate master outputs to accommodate different connections. These can be used to the same ends, but it won’t be as simple as plugging it into your laptop.

Enhanced EQ

Any mixer will have at least a primitive EQ built in – fixed-frequency bass and treble – but if you can find one with more detail, that would be preferable. Some include a control for mids. Some include controls for low mids and high mids. Some even include one or two variable mid controls, allowing the user to select the frequencies affected. The point is if you can find more controls for EQ, the more precise your mix could sound. Just be aware that these extra controls across several channels will drive up the cost of a mixer significantly.

Internal Effects Send/Return

Some mixers feature a built-in effects section. This is incredibly handy in live situations because it allows the user to utilize basic enhancement tools like reverbs and delays on all of the individual inputs. The quality of the effects may vary, but technology has improved to the point where even cheap effects sound decent and can be useful if applied judiciously.

Internal Dynamics Processing

Some mixers come with compressors or limiters available on some or all channels. These allow the user to apply compression to specific channels as an insert effect. This is extremely handy for vocals and acoustic guitars.

The big digital mixers, like Behringer’s X32, Midas’s M32, or Allen & Heath’s QU32 include all of the above and then some. Regardless of what the analog purists may say, these digital mixers – albeit still a few thousand dollars – are some of the best bang-for-your-buck out there.

Typical Situations

Solo Performer (e.g. Singer/Guitarist)

This is the least demanding situation out there. You need two channels with at least one preamp, though most mixers are built with preamps in pairs. Ideally, you also need an input for a media player. This could be as simple as an extra stereo channel. You may be able to forgo sends, though I wouldn’t recommend it. In a case with no sends, you can always use one of your mains as a monitor since you will not be panning anything.

Bare Minimum Needs list:

• Two channels/preamps
• 48V Phantom Power
• Aux Input (for media player)

Full Band – Small Combo

The demands for this situation will vary greatly depending on your band’s instrumentation and how detailed you plan on miking your drummer. Drum miking is a topic all on itself, but in the scope of this article, let us assume you want to mic at least two drums – the kick and the snare. Just bear in mind that any additional drum mic will cost you an additional preamp and channel. Likewise, each additional singer or instrument will cost you the same, though instruments that send line-level signals will not require a preamp; just a channel.

So, for our example, let’s assume a rock quartet – drums, bass, two guitars, two singers.

Bare Minimum Needs List:

• 7 channels/preamps – kick, snare, bass, guitars 1 and 2, vocals 1 and 2 (Round this to 8 – mixers are only made with even numbers of channels)
• Sends (at least one – preferably two or three)
• 8V Phantom Power
• Aux Input

Electronic Music Performers

It’s very difficult to describe a bare-minimum for this type of a situation because the needs will vary drastically depending on the the artists’ setups. Some artists use a standard, portable mixer. Others prefer the unique features found on a club style DJ mixer. Others may also employ a MIDI controller as a mixer, preferring to run all of their audio through a performance-oriented DAW like Ableton Live.

There are so many variables to consider with a live electronic rig that it’s difficult to outline what is needed. Still, there are minimum requirements to consider.

Bare Minimum Needs List:

• One channel per device. (This includes your computer, if you are not using a DAW as your mixer already. It also may vary depending on whether you chain devices together)
• Sends (at least one)
• 8V Phantom Power

DJ’s

Selecting a DJ mixer is outside of the scope of this article. DJ’s shouldn’t need a section here because their mixer is their instrument – if you’re a DJ, you should already have a mixer!

Conclusion

Choosing a mixer for your setup is a crucial decision to make, so it’s important to consider your needs as well as giving yourself some leeway. The best practice is to consider your bare minimum requirements and purchase a mixer that offers just a tad more — a couple extra channels, sends, and/or features.

-AudioMunk