When you look at an audio mixer, it can be kind of intimidating. However, as you’ll see in this video, it’s a lot less complicated than it looks.
Right here, I’ve got a Mackie ProFX12v3+, but what I’m about to teach you can be applied to almost any analog mixer on the market.
Thanks to Mackie for sponsoring this video and supporting audio education.
Basic Layout
Most analog mixers will have the same basic layout.
There are inputs for connecting sources, such as microphones. Each input has its own line of controls, called a channel strip. There are also outputs for connecting to destinations, such as speakers or recording devices.
You can use a mixer like this for anything from live streaming and podcasting, to recording music or running live sound at an event.
For the sake of understanding the features and controls of a mixer, picture this scenario: You and I are running sound for an event with live music.
The system includes two powered speakers for the audience and one powered stage monitor for the performer.
The musician on stage will be singing and playing acoustic guitar and we’ll record the performance to a laptop.
When the musician is taking a break between sets, we’ll play background music from a tablet.
Outputs
We can start by connecting the outputs to the speakers.
The main speakers (for the audience) will be connected to the ‘MAIN OUTS’. In this case, we can use an XLR cable from ‘MAIN OUT LEFT’ on the mixer to the input on the left speaker and another XLR cable from ‘MAIN OUT RIGHT’ on the mixer to the input on the right speaker.
The Mackie ProFX12v3+ gives us the option to use either XLR or TRS, but you can always use an adapter if needed. XLR and TRS are basically the same connectors. The adapter you’ll need just depends on the type of connections on the mixer and the speakers.
The ‘MAIN OUTS’ are controlled by the ‘MAIN’ fader. This is commonly called the ‘Master Fader’ and it can almost always be found in the bottom right corner of the mixing console.
You can think of the ‘MAIN’ fader as the volume control for the ‘MAIN OUTS’. Just above it, you’ll find a mute button that mutes everything coming out of the ‘MAIN OUTS’.
In a moment, I’ll explain how to route our input sources to the main speakers. But first, let’s set up a stage monitor for the performers so they can hear themselves play…
We can set up a stage monitor using an auxiliary output, such as the ‘MONITOR SEND’ on this mixer. In this case, we only have a ¼” output, so we’ll use a ¼” TRS to XLR adapter and a long XLR cable to the input on the powered speaker.
Similar to the ‘MAIN OUTS’ being controlled by the ‘MAIN’ fader, the ‘MONITOR SEND’ output level is controlled by the ‘AUX MASTER’ knob.
Next, we need to set up the recording. There are a few ways to do this.
1) We could connect the mixer directly to the laptop via USB and record directly into a DAW using the built-in audio interface within the mixer. In ‘STANDARD’ mode, this option will record the signal that is sent to the ‘MAIN’ fader.
Or, option number 2… We can connect the ‘SUB 1-2’ outputs to the inputs of a stand-alone audio interface using TRS cables. Let’s go with this option, because you may not always have a mixer with a built-in USB interface.
You’re probably starting to see that each of the physical outputs on the mixer is controlled by a dedicated knob or fader here in the master section. The ‘SUB 1-2’ fader controls the level of the ‘SUB 1-2’ output.
There’s one more very important output that we will want to set up – the ‘PHONES’ output. The reason a headphone output is so important is that it allows us to check the audio BEFORE the audience hears it.
On the mixer, there is the headphone jack and its output level is controlled by the ‘PHONES’ knob.
Inputs
Now that we’ve connected the outputs of the mixer to the destinations, let’s connect our sources. Remember – the inputs include vocals, acoustic guitar, and background music.
I always start by testing the system with music from my smartphone or tablet, and this mixer offers us a few different ways to do that.
With channel ‘11/12’, we can connect via Bluetooth or an ⅛” aux cable. For this demonstration, I’ll connect my tablet with Bluetooth and start playing some music. We don’t hear anything yet though.
This vertical line of controls is called a channel strip. At the bottom of each channel strip, we see a channel fader and a couple of buttons.
One of these buttons is the ‘PFL/SOLO’ button. (It’s called ‘PFL’ for “pre-fader listen”, which means what we hear when we press this button will be unaffected by the fader position.)
Pressing the ‘PFL/SOLO’ button will send the audio from channel ‘11/12’ to the ‘PHONES’ output. Now I can hear the music from the tablet playing in my headphones and I can see the signal on the ‘MAIN METERS’.
Based on this meter, I’m going to adjust the output level of the tablet. Yellow lights are ok, red lights are not ok. I’ll aim for the signal level with peaks around (or just over) 0 dB.
It sounds clean in the headphones, so I’ll disengage the ‘SOLO’ button.
Now we can bring the music up in the speakers. First, we need to unmute channel ‘11/12’. Then we need to select which output to send it to with these routing buttons.
The ‘1-2’ button routes the signal to the ‘SUB 1-2’ output, which is currently connected to an audio interface for recording. We don’t need to send the background music to the recording, so let’s leave the ‘1-2’ button disengaged.
The ‘L-R’ button routes the signal to the ‘MAIN’ output, which is connected to the main speakers where we want to hear the music. So, let’s press the ‘L-R’ button.
Now, when we push the channel fader up, the signal from channel ‘11-12’ will be sent to the ‘MAIN’ mix. However, the ‘MAIN’ fader is currently pulled down and the mute button is engaged. If we want to hear something through this output, we need to unmute it and bring up the fader.
We can bring up the ‘11/12’ channel fader and we start to hear the music play out of the main speakers.
Before going any further, we need to adjust some levels. If the music is extremely loud when you even slightly bring up the ‘11/12’ channel fader, we should probably turn down the volume of the amplifier or powered speaker.
Ideally, the music in the room will be at an appropriate level when the ‘MAIN’ fader and the ‘11/12’ channel fader are at the 0dB mark, also called unity gain (or ‘U’ for short). If needed, you can pull down the ‘MAIN’ fader to accomplish this, but it’s better to keep the main fader at unity and adjust the amplifiers, especially in extreme cases.
(As you become more experienced, you’ll understand that this rule is made to be broken. But I think this is a useful guideline for beginners.)
There are a couple of reasons why you want THESE TWO faders to be at (or around) unity gain. The first is to utilize the full dynamic range of the mixer. We test the system with mixed music at an appropriate level on the meter so we can get an idea of how loud our mix will be in the room during the show.
The second reason to keep faders at (or around) unity gain is that the fader scale is not linear. A small movement of the fader in the shaded area will result in a relatively small change in level compared to a small movement of the fader down here at the bottom. So keeping the fader near unity gain allows us to make subtle adjustments much more easily.
If this mixer didn’t have Bluetooth or ⅛” connectivity, we could have used channel ‘9/10’ with an ⅛” to dual ¼” TS adapter. The same setup process would apply, otherwise.
You may be wondering why the channels so far have been labeled with pairs of numbers, like ‘9/10’ or ‘11/12’. The reason is that these are stereo channels, which facilitate the stereo left and right audio channels of the music.
Next, we need to connect the vocal microphone and acoustic guitar, which will each be mono inputs.
Let’s connect the vocal microphone to ‘INPUT 1’ using an XLR cable. We will assume that we’re using a dynamic microphone like this one, which doesn’t need phantom power. But if it were a condenser microphone, I would engage the 48V button over here.
The acoustic guitar could be set up with another microphone, but in this case, we’ll assume it’s an acoustic-electric guitar so we’ll connect the built-in guitar pickup to ‘INPUT 2’ with an instrument cable.
Because ‘INPUT 2’ is connected to an instrument directly, I’ll press the ‘HI-Z’ button to put this channel into high-impedance mode.
By the way, using an instrument cable is fine up to about 15-20 feet, but if you need to run the signal over a longer distance, check out my video on DI Boxes linked in the show notes below.
Once the vocal microphone and guitar are connected to the mixer, the next step is to check these sources in headphones. Again, we do this by pressing the ‘PFL/SOLO’ button at the bottom of the channel strip.
As you can see, the signal is pretty weak on the meter. We need to boost the signal level using the preamp gain knob at the top of the channel, aiming for peaks around (or just above) 0dB.
Side note – the Mackie ProFX12v3+ has an analog level meter. That’s why it’s ok if peaks go slightly beyond 0dB. But if we were using a mixer with digital metering (or full-scale metering), the 0dB mark would be at the very top. In that case, clipping will occur at 0dB so we would aim for signal levels that hover around -12 or -18 dB on the DAW meter to give the signal some headroom before clipping.
Now that we’ve verified a clean vocal signal with headphones, we can un-SOLO ‘CHANNEL 1’, assign it to the ‘MAIN’ bus using the ‘L-R’ button, and bring up the fader. Now we hear the vocal mic in the speakers.
While we did not want the background music from the tablet in the recording, we DO want the vocal mic in the recording. To do that, I’ll also send ‘CHANNEL 1’ to the ‘SUB 1-2’ bus by pressing the ‘1-2’ button.
Remember – we need to unmute ‘SUB 1-2’ and bring up the fader in order to send audio out of the ‘SUB 1-2’ output.
Once we have ‘CHANNEL 1’ set, we can mute it and go through the same steps for the acoustic guitar on ‘CHANNEL 2’…
Check the audio in headphones using the ‘PFL/SOLO’ button on ‘CHANNEL 2’…
Set an appropriate input level with the preamp knob at the top of the channel strip…
Un-solo ‘CHANNEL 2’, assign it to the ‘MAIN’ bus with the ‘L-R’ button and the ‘SUB 1-2’ bus with the ‘1-2’ button, and pull up the fader.
Once that’s set, I’ll mute the guitar channel as well.
Channel Strip
At this point, we will be able to hear each input source in the speakers, but it may not sound very good just yet.
First, notice that all of the channel strips are more or less the same, depending on the type of input. This means you just need to understand one channel strip to understand all channel strips.
At the top of the channel strip for ‘CHANNEL 1’, we see the Hi-Z button. We’ve already learned that this is for connecting high-impedance sources like guitar pickups. We will leave this un-pressed for our microphone channel.
Just below this, we see an ‘INSERT’ connection. Let’s return to this in a moment.
Next is the ‘LOW CUT’ button. When this is pressed, the lowest frequencies (below 100 Hz, in this case) will be attenuated (or reduced). The human voice doesn’t have much information below 100 Hz anyway, so engaging this switch will remove unnecessary low frequencies without really impacting the sound of the vocal signal itself.
The same goes for the acoustic guitar on ‘CHANNEL 2’. Engaging the ‘LOW CUT’ is particularly useful in live sound, where low frequencies tend to feedback very easily through the speakers.
We’ve already set the preamp gain knob for each input, so let’s continue on to the ‘COMPRESSOR’ knob. A compressor can be used in different ways. One thing you can do with compression is smooth out the dynamic range of a performance, reducing the difference between the loud parts and quiet parts.
The more you turn up this knob, the more the compressor keeps the loudest parts in check. This might be helpful for smoothing out the vocal or the guitar – we just need to listen and adjust accordingly.
Keep in mind – compression can be very subtle and kind of difficult to hear if you’re not trained for it. Just keep practicing and you’ll get a hang of it.
As we move further down the channel strip, we find the EQ section. This mixer has a 3-band EQ: ‘HI’, ‘MID’, and ‘LOW’. You can boost or cut the specified frequencies with the corresponding knob.
The frequency of each band is fixed on this particular mixer. However, you may come across mixers (such as the Mackie ProFX16v3+) with a variable frequency control that allows you to specify the frequency and specify how much to boost or cut it.
I’d generally recommend cutting versus boosting when possible. If the vocal sounds muddy, I could either boost with the ‘HI’ band or cut with the ‘LOW’ band.
The compression and EQ settings are completely dependent on the situation – and sometimes you’ll use no compression or EQ at all. In fact, it’s better to not use compression or EQ than to use compression or EQ for no reason. So use your ears and adjust accordingly.
Below the ‘EQ’ section, we see the ‘AUX’ send knobs. The ‘MONITOR’ knob determines the amount of each channel to be sent through the ‘MONITOR SEND’ output, which currently feeds the performer’s stage monitor.
Again, we need to turn up the ‘AUX MASTER’ knob to send audio to the stage monitor. In this case, unity gain is at about 50%. There is a detent when the knob reaches that position, where the knob locks into place to let me know that’s the default setting.
We will set the ‘MONITOR’ aux send knobs on both ‘CHANNEL 1’ and ‘CHANNEL 2’ to provide the performer with a comfortable mixture of vocal and guitar in their monitor.
The ‘FX’ knob below could be used as a second monitor send if we had two musicians on stage who needed different amounts of each source in their stage monitors. The signal would come out of the ‘FX SEND’ output just below the ‘MONITOR SEND’ output.
But in this case, we will add some reverb on the vocal and guitar using the ‘FX SEND’.
First, we need to unmute and bring up the fader on the ‘FX RETURN’. Then, we can use the ‘FX SEND’ knobs to apply reverb to each channel.
If you had an external reverb unit, the signal could be sent out of the ‘FX SEND’ output, into the input of the reverb unit, and then the output of the reverb could come in on a separate mono or stereo channel.
Here, the reverb is built into the mixer, but the signal flow is essentially the same. Send with the FX send, return on the ‘FX RETURN’. You can experiment with sending MORE to the reverb and bringing DOWN the return fader or sending LESS to the reverb and bringing UP the return fader.
We can also send some of the reverb to the musician on stage with this ‘FX TO MONITOR’ knob.
And if we want reverb in the recording (which we do), we can press the ‘1-2’ button on the ‘FX RETURN’.
The next knob on the channel strip is the pan knob. With stereo left and right speakers or stereo recordings, this controls where the input is positioned in space.
Turning it all the way to the left directs all of the signals to the left ‘MAIN OUT’ and ‘SUB OUT’ channels.
Turning it all the way to the right does the opposite.
With the pan knob in the center, the signal will be routed to both left and right outputs evenly.
And now we’ve reached the fader, which can be used to create a good blend between all of the different channels. This control can be used throughout the show when the level of an instrument needs to be adjusted.
Before I forget – let’s go back to the ‘INSERT’ connection toward the top of the channel strip… This is the connection you would use to “insert” a piece of external hardware into this channel strip. While we typically integrate a reverb FX processor by sending the signal out and back in on a SEPARATE channel, we usually integrate an external EQ or compressor by sending it out, through the device, and back in on the SAME channel.
You set it up using an insert cable like this one, with TRS on the mixer side and two TS connections to the external gear – an output and an input.
In conclusion, understanding the layout and functionality of an audio mixer can greatly simplify its operation, making it a versatile tool for various audio needs, from live events to studio recording sessions.