Intro to Mixers Part 1

This Series is meant to be a quick intro small audio mixers, and some tips on how to get the most out of the one you’ve got.  This section will be an intro to channel strips.

 

There’s thousands of models and hundreds of brands out there with consoles as small as 2 channels and as big 300 hundred channels.  But I’m going to focus on the ones that a lot of bands might consider buying if they’re just getting started.

 

For starters lets give a little background info

 

A mixer is simple a box with lots of inputs and outputs.  They allow you to add individual audio signals (channels or tracks or instruments) together and create a “mix.”  Usually you’ll be mixing to stereo, which just means there is an independent Left and Right Channels.  

 

Mixers have lots of identical columns of knobs and buttons on them, called channels.  Each channel is like an independent audio track on your mixer.  When you want to make changes to just one track, the channel strip is where you’ll make that change.

 

The basic “flow” of your audio through a channel is usually something like this: 

 

Input jack -> Gain (Preamp) -> Insert -> High Pass Filter -> EQ -> Fader ->Pan -> Output Assignment

 

1) The Input Jack is simple enough.  There is an XLR (mic cable) jack for hooking up mics and usually a ¼” (guitar cable) jack for hooking up keyboards, basses or guitars directly into the mixer. 

 

2) The Gain knob is probably one of the more important knobs on the channel.  It is the first time your mic or instrument gets amplified.  Most mics put out a very low volume signal and need to be brought up in order to be processed and mixed with other sounds.  It basically allows you to set the incoming volume to a good level for you to tweak it with the mixer.

 

The gain knob is usually the volume adjustment with the most “tone” or “character” to it, unlike Faders which are designed to be more “transparent.”  As such, it is often the Gain or Preamps that give a certain brand or model of mixer it’s “sound.” 

3) Insert Jack are found on some mixers after the Mic Preamp, but before all the processing.  This isn’t always the case, as sometimes you’ll find them after the High Pass Filter, after EQ, or even switchable to different locations.  The basic use is for you to add an inline processor to your channel.  A compressor, Eq, de-esser, etc can be added to your channel.  This is where “outboard” comes in, and it’s also used on some mixers as Direct Outputs.  These jacks usually take stereo cables that split into two mono cables on the other end.  

 

4) High Pass Filters are usually the next stop of your audio.  You’ll usually find a knob or button for the filter right underneath the Gain knob.  It is basically a device used to cut out the Low Frequency (bass) part of a signal. 

 

How-to: As an Example, most guitar amps put out more bass than is actually needed to hear and understand the part being played.  This lower frequency “mud” tends to make the Bass and other low instruments harder to hear, so we cut the Mud out of other instruments to protect that low frequency zone.

 

Some mixers let you choose what frequency you start to cut at and will provide a knob to select it.  Different Engineers like different cuts, but most agree that Below 50-60 Hz, there’s isn’t a lot of musically useful stuff. Of course if you’re recording music destined for dance clubs or an audience that just loves to hear that sub, you can probably cut lower. 

 

Other mixers include a set frequency cutoff and just provide a switch to turn the filter on an off. 

 

How-to: These are great for live performances, or on mics that get all those “handling thumps” when your singer grabs the stand or runs around with the mic. 

 

Some mixers just don’t include them to cut down the cost of the mixer.

 

5) The EQ is probably the section most musicians are familiar with.  They work a lot like the treble/bass or hi/mid/low knobs on your guitar amps.  They let you select bands of frequencies to cut or boost on a signal. 

 

Most Small mixers have a Hi knob that lets you cut or boost frequencies above 8-12 kHz, which is often thought of as the “air” or “sizzle” part of a sound.  It can also be really harsh on the ears if overused and often makes noise and buzz in the system more apparent so listen carefully when you use it.

 

A Low know gives you some control over lower frequencies. Usually letting you cut or boost frequencies below 80-100 HZ.  The same warnings go with the lows knob as pumping this on a smaller sound system can be bad for the speakers, can make your mids harder to understand, and boost funky low noises or hums in your system. 

 

The Mids of a mix are usually the hardest part for mixers to get right.  Everything has a claim on that part of your mix: Guitars, Vocals, Snare Drum, some Bass notes, Keys, Horns, etc.  Because of this, most small mixers will give you a Mid knob that lets you “sweep” your boost or cut up and down a range of frequencies.

 

If that’s the case, then you’ll get a knob for turning the boost up or down, and another knob to choose the Center Frequency.  Say you choose 1kHz as your center.  When you turn up the mids, 1kHz will be boosted but frequencies close to 1kHz, both higher and lower, will also get boosted, just not as much.  

 

How-to:When I’m searching for the right frequency I tend to do an exaggerated boost and then sweep the frequency knob until I hear something I want to accentuate or get rid of.  Then I readjust the boost to be a smaller boost or a cut depending on what I want. 

 

6) The Fader is probably the coolest part of a sound board.  Admittedly, it’s the part I love the most.  Faders lets you turn signals up and down in the mix. 

 

Now wait a minute… isn’t the Gain knob for turning up a signal?  Well yes, but the Gain and Fader have very different functions.  The Fader isn’t designed to add character or tone to your sound as much as its meant to adjust the volume relative to other tracks.  The Gain knob isn’t a great tool for mixing because the amplification it makes its far more powerful than that of the fader, and its harder to make small adjustments.

 

Take a look at the signal flow again and the MAIN reason you have both a fader and gain will become apparent.  The Gain knob is your way to set volume before you make EQ changes or use filters.  You want to use the Gain and processing to get the sound the way you want it by itself.  The Fader is how you set volumes after you’ve made your adjustments, and so it lets you leave the relationship of the EQ, and Filters and Tone of your sound unchanged while still being able to adjust a track in the mix. 

 

How-to: As a general rule, when I’m setting up the mix, I bring all the faders I’m going to use up to “Unity.” This is usually marked as “0” or “U” on the fader’s scale and it means that the volume coming to the fader is the same as the volume leaving the fader. 

 

Then I have some play or sing into the mic and slowly adjust the Gain knob until the it sounds good to me.  After that I almost never touch the Gain knob again- only adjusting it if the sound is far too low to be used or if the sound is clipping.  This ensures that my EQ adjustments aren’t messed with as I make adjustments to a mix with the faders. 

 

7) The Pan pot is pretty simple to explain.  It lets you move a track left or right in the stereo field.  In other words, panning left makes something louder in the left speaker and softer in the right. 

 

You might be wondering why I put the Pan after the fader, as on most mixers you’ll see it above the fader.  This is mostly because technically your signal hits a pan after the fader, although from a practical standpoint… doesn’t make any difference in how we use them. 

 

8) The last set of things your signal hits on a channel is usually an Output Assignment.  Some mixers have alternatives to the main output called Tape out, Alt 3-4, Sub 1-2, etc.  Every mixer varies in how you assign where to send your channel, but most give you a set of switches.  Engaging a switch lets you send it out that output.  Engaging multiple switches lets you split your signal to multiple locations (the volume doesn’t split in half, it just makes an identical copy and sends them to two different places).

 

9) You’ll also encounter mixers with Inserts  and/or Aux or FX Sends. I’m putting these last, but they actually play a peculiar role in signal flow.

 

Inserts and Aux Sends are built into mixers to allow you to add different kinds of processors to your mix.  With Inserts, you intercept the signal on a channel (Usually after the EQ and Before the Fader) and send it to another unit like a Compressor and then return the signal to the board right before the fader.  It’s basically like adding an extra step in signal flow. 

 

10) Lastly, you may encounter a small mixer with Direct Outputs.  These are great to have, but really rare on smaller budget models.  A couple that do have them are the Mackie 1604 and Allen and Heath Mix Wizard.  (You can also use your Inserts as Direct Outputs – more on that here.)

 

These Direct Outs allow you to make a copy of a signal right after the Gain (Preamp) knob and send it to a recording device.  Direct Outs are predominantly used in recording situations where the main outputs are being used for something else, like at a live show.  The mixer’s main outs are being used to mix the show to the speakers, but directs out allow individual tracks to be recorded separately without recording all the EQ changes or volumes used in the show, which might not be ideal for a recording.  

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