Understanding Your Mixer: The Channel Strip
We don’t do a lot on live sound at Audiotuts+, but it’s an essential area of knowledge every musician should have. After all, no matter how many tracks you record in a studio or at home, nobody will know who you are until you get out there and play for someone. One thing that’s stopping more artists from taking this step is their fear of the big fancy mixer. It’s quite a bit different to the mixer in Logic and Pro Tools.
Due its vast array of controls, many find it intimidating, but it’s really nothing to be scared of. Let’s take a look.
The Strip Layout
The mixer has plenty of controls on it that can make it look rather intimidating, but there’s no reason to feel this way. Instead of having to learn 16 or 24 columns full of controls, you really only need to learn one (plus some master controls). That’s because those strips of buttons and dials are all pretty much identical to those surrounding them — there’s just one for every input you can jack into the mixer.
We’re going to look at the channel strip in detail, followed by the master controls. Then we’ll take a look at how you about setting up your mixer for a gig.
Here’s an image of a Yamaha mixer’s channel strip. Click on the image for a larger version:
Keep the image open beside this tutorial and we’ll go through each element of the strip as numbered.
1. XLR microphone input
This is where your microphone lead connects to the mixer. Signals that are coming in through this input are generally mic level inputs (remember this as it will be important later).
2. TRS balanced line input
This is where line inputs such as CD players, bass guitars, and (less frequently) guitars are plugged in. Guitars don’t sound great this way, but your average external sound source will sound fine, and often bass is cleaner this way than through an amp.
On any stereo channel strips, there’ll be a line input for both left and right sound sources.
3. Insert input/output
Insert jacks are used to connect the channel to an effects device, such as an EQ, compressor or reverb. They require an insertion cable, which has three connectors — one for the input and output from the insert jack, one that sends the channel output into the effect processor’s input, and one that returns the sound from the effects processor to the channel.
If you’re more familiar with DAWs, think of this like a send/return.
This button controls a 26dB attenuator. If the signal is coming in too loud even with the gain control set to zero, turn this on to control it. Some mixers will say “Pad,” some will say “26dB” and there are a few other less common variations.
5. Gain control
The gain control adjusts the amount of gain that’s applied to the incoming signal. This is the control you use to set up what’s called a gain structure, and you’ll need to adjust this as necessary for different input types such as mic, line and instrument levels.
6. High pass filter
On almost all mixers you’ll have a high pass filter. It’s usually marked with the letters HPF or with an 80 under a bent line. If this button is pushed in, the mixer will cut frequencies below 80Hz on that channel. I like to start out by having this button pushed in on every channel to control bottom-end, and if the mix feels a little thin in terms of bass I can take it off on the bass guitar and bass drum channels.
7. Compression pot
This little knob is essentially a compression ratio control. Many mixers won’t have one of these (you’ll need to use the insert jack to use an external one), but those that do either have a preset compression threshold or more advanced controls elsewhere on the mixer.
It’s safe to say that most serious productions will use outboard equipment for this purpose, but if you do get a mixer with this feature and don’t have the cash for hordes or rack gear, it’s quite convenient.
8. EQ: High frequency
The first equalizer pot adjusts the channel’s high frequency band. The default position for this knob is in the centre, rather than the far left as with most controls. Turn left to reduce high frequencies and right to boost them.
9. EQ: Middle frequency center
If your mixer has two pots under the heading “MID”, it’s a mixer that allows you to adjust what the mid frequency range encompasses. The top knob allows you to set the centre frequency of that range.
10. EQ: Middle frequency
The second knob under the heading “MID” — or the only knob in some cases—works the same as the high frequency pot. The default position is in the centre, and you turn it left to attenuate mids and right to boost them. Use it in tandem with the mid center control to adjust the frequencies you’re attenuating or boosting.
11. EQ: Low frequency
This pot adjusts the gain of low frequencies. Again, centre the knob for a default setting, and turn it left to attenuate and right to boost. If this knob isn’t having much of an effect, try turning off the high pass filter.
Note on equalizer functionality: Your mixer’s manual will tell you exactly what frequencies each pot encompasses (or can encompass depending on the ability to set ranges), and how much you can cut or boost these bands.
12 & 14. Auxiliary bus levels
These knobs adjust the signal level sent to the bus for auxiliary one and two respectively.
13 & 15. Pre/post-fader switch
This button determines whether the auxiliary knob it’s sitting beneath is sending a pre-fader or post-fader signal. If the switch is on, the channel’s fader won’t effect the signal sent to the auxiliary bus — only the auxiliary level pot will.
16 & 17. EFF 1 & 2
If your mixer has effect buses, these knobs function much like the auxiliary bus pot and determine the amount of the channel’s signal sent to the effect buses.
18. Pan control
The pan control works just like it would on your DAW mixer — it determines where in the stereo spectrum the signal will sit. Unsurprisingly, turn the knob to the left and the sound will sit further to the left. Turn it to the right and it’ll move to the right. If it doesn’t, check your speaker wiring.
On stereo channels, this will be a balance control that allows you to place the left and right signals where you want them. Most of the time, this will be hard left and hard right.
19. On switch
This switch simply turns the channel on or off. If you’re not using a channel, keep it off, so that any inherent noise is controlled. Considering that noise will be sent to the summing mixer, the auxiliary buses and insert buses, it can certainly add up, particularly on older mixers.
20. Peak & Signal LEDs
These little lights provide you with some basic, but important information:
Peak tells you when the signal is getting close to clipping level (it usually warns you 3dB below clipping). This is essential during mixing for ensuring that the signal stays hot, but not hot enough to risk a loud clip.
Signal merely lights up when a signal is being fed into the channel. It’s good for confirming that everything is coming through okay or tracking down the noisy channel that’s not meant to be on.
21. Pre-fader listen switch
If you see a button that says “PFL”, it’s a pre-fader listen switch. When you switch this on, it sends the channel’s pre-fader signal to the headphones jack so you can monitor the direct signal. This is good for checking the sound of mic positioning and amp levels right before you make changes through the mixer itself.
You can also monitor pre-fader listen signals even when the channel is set to off.
22. Channel fader
The one part of the mixer that almost everybody knows is the channel fader. This adjusts the signal’s output level, and allows you to achieve a balance of levels between the channels of your mixer, a process we sometimes refer to as mixing!
Setting Up Your Channel Strip
So now you know what all the fancy buttons do on each channel strip, and it’s not that complicated after all. Now you need to learn how to set up a channel strip using those controls!
We’re assuming that the mixer is ready to use, and set up to work with the speakers in the room properly. It’s not turned on yet. Though this tutorial focuses on the channel strip and how to configure it, we’ll cover the rest of the mixer in tutorials to come.
1. Plug your input in
Wait, no! It’s what you were probably thinking, but hold onto your horses. First, zero out all the controls — that is, put them back to their default positions. This is a matter of just turning them all to the left, except for the EQ and pan controls, which should be centred.
Pull all the faders down as well, including the master fader. Most importantly, ensure the gain control is turned to the left.
Also ensure that each channel strip’s ON button is in fact set to the off position.
2. Now plug your input in
Get the other end of your lead, whether it’s a microphone or a line-in connector, and plug it into the appropriate input.
3. Use your HPF
Go and turn on the HPF for all channels, except for those channels for bass instruments. Some (including myself) like to start with the HPF on for these channels as well and take them off if there’s not too much mud, but it’s up to you.
4. Set your pads
If you think any particular sound source is likely to be very loud, push the pad button. You can easily turn the pad off if you’re not getting any signal.
5. Remember phantom power!
If you’re using microphones that require phantom power, turn it on. If you turn this on, don’t use ribbon microphones or very old dynamic microphones.
6. Turn the mixer on
Now that you’ve got your inputs going into the mixer, with the faders right down and any HPF and pads on, you can turn the mixer on without having to deal with the loud pops and bangs that can result from plugging things in and out (and potentially destroy speaker cones).
7. Turn on the PFL
Turn on the pre-fader listening on each channel you are going to use. You need to monitor pre-fader when setting up the gain structure.
8. Gain structure!
This is the most important part of setting up your mix, and that’s gain structure. The gain knob will show you the gain range for mic and line inputs — on the channel strip image we’ve got, it shows -16 to -60 for mic inputs and +10 to -34 for line inputs.
Start with this knob turned completely to the left and have the musician controlling the instrument or sound source plugged into that channel make as much noise as loudly as they can. Increase the gain until the peak indicator lights up only when the musician is playing slightly louder than the maximum volume they’ll play at throughout the performance.
It’s a tough balance to strike as you don’t want to risk frequent clipping, but you don’t want a dull signal, either.
You want to get each instrument’s gain set to a certain level so that all channels are playing at the same volume when set to unity gain on the channel fader (0). This will be a different level of gain for each input type and each type of instrument (for instance, playing a trumpet straight into a microphone is a lot louder than someone singing into one, and will not need slightly less gain than the singer’s microphone).
9. Turn the channel on
At this point you may turn the channel on using the large “ON” button above the peak and signal indicators.
10. Repeat this process for each channel strip
Set up each channel strip so that the signal is coming through at the same level. The faders should all be at 0.
11. Set the master fader
To begin your mix, you want the master fader to sit at 0.
12. Mix your channels
With the gain structure set, you’re free to use the faders to mix the volume of the different sound sources together. When mixing with the channel faders, ensure that you’re listening to the speakers, not the headphones. Use headphones for pre-fader listening when you need it.
13. EQ and effects
Once the instruments are sounding as good as possible on their own, use the onboard or outboard EQ and effects to enhance the sound. You want to wait until this stage because effects should be used in moderation to enhance sounds, not to fix them, if at all possible. If you’ve done what you can to fix the sounds without effects, this is the first time in the process you should allow yourself to resort to such measures.
Remember to cut frequencies before you boost, and when you do boost, do it as little as possible. If the kick drum isn’t getting enough punch across, try rolling off the lows of other instruments such as piano and electric guitar that produce a lot of sound in those frequencies that you don’t need. Your first instinct should not be to boost the bass on the kick drum.
14. Mix your channels (again)
Generally, once you introduce EQ and effects, the levels of each channel change slightly. If you added some reverb, then the channel’s signal will be louder, and if you took out some bass or mids on the EQ, the channel’s signal will be much quieter. Adjust the mix to compensate for any of these changes.
15. Check the room
While not specifically related to the configuration of the channel strip itself, I’m sure this step will help you find any problems with the sound that can be fixed using the channel strip controls.
Once you’re happy with the mix from the centre of the room, take a stroll (or a hike, if you’re mixing in a stadium, in which case you’re probably experienced enough that reading this has been a waste of time!) and ensure that all areas of the room sound good.
Keep in mind that standing close to the front is going to have a proximity effect with extra bass heard in the mix, and standing near the back is going to be much thinner. You only want to try and fix real problems in the mix that other vantage points might make more apparent to you, not the natural loss of low frequencies over the length of the room. If you try and battle the room, you’ll wreck the mix.
So now you know how to set up each channel strip and you can tell grandma what each control does! But this tutorial assumes that someone set up your mixer for you, and doesn’t teach you how to work with effects and groups. Check back next time for this and more in the Understanding Your Mixer series.