Layout of a Mixer

-A mixer can be quite daunting, so many faders and knobs…

When looking at a mixer it is important to look at it as a set of duplicated columns.  The first column starts with a microphone input, a ¼ inch input, an insert, a set of knobs, and then at the bottom a fader or a volume knob.  This vertical column is call a channel strip or more simply called a channel and more specifically channel one.  The first channel of a mixer is duplicated horizontally across the mixer.  The reason we call a channel a channel strip is because each individual component or more simply put every knob can be used to manipulate the way a microphone or instrument sounds.  There are several typical components of a mixer and each component is in a specific order or signal flow when being connected so that the input source can be most effective.



-Signal Flow Example


Channel Strip Layout on a Mixer

1- Mic Input

2- ¼ Input

3- Insert

4- Gain

5- Low Cut

6- -20db Pad

7- EQ

8- Auxiliary

9- Effects (pre/post fader)

10- Pan

11- Mute

12- Volume (Fader/Knob)

13- Routing Options (PFL / 1-2)




1- Microphone Input


Most mixers have a 3 pin female microphone input located either at the top of the channel strip or on the back of the mixer.  These 3 pin female inputs are meant for an XLR cable or more commonly referred to as a mic cable.  As combination inputs have become much more popular, instead of a mic input there is often a combination jack.  An XLR cable is still used with a combination jack.  If you look close you can see the 3 circular holes that are meant for an XLR cable.  The combination jack also accepts a ¼ inch cable.  Next we will look at the next input on a mixer.


2- ¼ Inch Input


After the microphone input, we see that there is a ¼ input that is next on the channel.  Make sure to read below the ¼ inch input and that it reads “INPUT”.  If it says insert then your mixer may be using a combination jack or your mixer does not have a ¼ input.  Now, if your mixer has a ¼ input then you can use these inputs for anything that uses a ¼ inch cable.  Guitars, pianos, mics, etc…  There are several different instruments and sound sources that can use a ¼ cable, even cell phones can use an ⅛ inch to ¼ inch cable to play music (refer to the cable chapter for more information).



3- Insert

Insert can be quite deceiving of a term.  Though insert looks like regular ¼ inch input, the ¼ inch slot labeled insert is not a regular input for an instrument.  Insert is used to add some kind of external processor to be inline with the channel.  Specifically the insert allows you to “insert” an external processor like a “compressor” between the mic input (1 on the above chart) and the gain knob (4 on the above chart).  




Now it is important to explain how an insert works.  Remember when we were going over TRS (Tip Ring Sleeve) cables and I brought up a Y cable.  Well now we are going to clarify when you would use a Y cable.  The insert on a mixer is a ¼ TRS input, but this input is built to send and receive audio.  This means that if we connect the TRS end of a Y cable to the insert we have two mono cables left on the other end. On of the mono cables is able to transmit sound out of the mixer and into an external piece of gear like a compressor.  For instance if we connect a singer and a mic to the mixer the singer’s voice will enter the mic input (1 on the chart) then travel through the inest and into the TRS end of the cable which then goes through one of the mono ends and into the input of the compressor.  Then the vocals are processed through the compressor.  Now we connect the left over mono cable to the compressor’s output.  Now the singer’s voice can travel out of the compressor and back into the TRS end of the cable which is connected to the insert on the mixer.  Now we have added a compressor into the channel strip by using a TRS Y cable.  


The insert section is important when connecting vocal processors, compressors, and gates.  We will go over these individual components later in the book.


4- Gain

Gain knobs on a mixer are actually controlling a preamp.  The word gain is simply referring to volume, and sensitivity.  So the gain knob on a mixer is controlling a preamp, a preamp is how a microphone is brought up to a volume that we can hear through speakers.  For instance, pretend we had a mixer that we could plug a mic into and on the mixer there was no “gain knob” or “preamp” but the mixer did have a volume knob down at the bottom of the mic channel.  Even if we turned the volume knob all the way up, we would not hear the mic.  Microphones are at a different volume level, which requires a preamp to be heard.  So overall, the gain knob is a preamp and it controls the sensitivity and initial volume of the mic.  A volume knob then controls the overall sound volume of the mic to the speakers.  So the gain knob essentially sets the volume of the mic for the mixer to control, then the volume knob that is located at the bottom of the channel strip controls the volume of the mic in the speakers.


5- High Pass Filter

This section may not be on all mixers.  The high pass filter button will usually just say 80hz and then has the button has a symbol which shows a low cut or high pass filter.  Low cut and high pass are the same thing.  Remember when we talked about the human hearing range is 20hz to 20khz.  So high pass means that the low frequencies are cut, in other words if the high pass filter says 80hz then it is cutting out 80hz and below.  Vocals for instance, do not go al low as 80hz, so we would use the high pass filter on any channels that a mic is plugged into.     highpass


6- 20db Pad

A pad is simply lowering the incoming volume of something that is plugged into a mixer.  There are times when a drum mic for instance, will sound distorted because the drum is so loud.  If the drum mic is plugged into the mixer and it sounds distorted and the gain knob is turned all the way down, the next step is press the -20db button.  This will lower the incoming volume by 20db and will clean up the distorted signal and create headroom.  Headroom is the amount of volume available before the source begins to sound distorted.


7- EQ

EQ Stands for equalizer.  

An EQ is generally with three different frequency groups is called a

  1. a three band eq,
    1. lows (bass)
    2. mids
    3. highs (treble) 


To better explain, the human hearing range is roughly

  1. 20 hertz all the way to 20,000 hertz,


we can roughly guess that

  1. lows are going to be in the 20hz to 400hz range
  2. mids will be in the 400hz to 1500hz
  3. highs from 1500khz to 20khz.  


On a mixer they will be in order from highs on top then mids and then lows.  Generally the highs and lows on a 3 band eq will be labeled at one specific frequency and the knob will say for instance

  1. -12db on the left side of the knob and +12db on the right side.  


DB means decibels, which is the way we measurement volume,  So

  1. if the knob for highs is labeled 2khz and
  2. you move the knob to the left,
  3. you will be lowering the volume of 2,000hz and
    1. also a few surrounding frequencies.

The shape of an eq curve is bell shaped, so when we are turning the knob to the left we are not only subtracting 2khz but also a bit of frequencies from both sides of 2khz in a sloped bell shape.


Now to explain how the section for eqing mid frequencies is laid out.  This eq is generally configured a little different. 

  1. highs and lows on a 3 band eq are set at one specific frequency,
  2. the mid range has the ability to select from a section of frequencies.

This is called a parametric eq,

  1. parametric eq has two knobs,
    1. a knob that is labeled frequency and
    2. a knob labeled “gain” with
      1. -12db and +12db.
      2. These two knobs should have a line drawn illustrating that the two knobs are connected in someway.  


A parametric eq allows you to sweep through different frequencies to zone in on a frequency causing problems.  A good exercise is to set the gain of the mids section to the left about a quarter of the way and then twist the frequency knob slowly to find and remove any problematic frequencies.  


8- Auxiliary

There are often at least two auxiliary knobs on an 8 channel mixer.  These auxiliary knobs can control the volume that is sent to a speaker on stage.  Each channel on a mixer has its independent own auxiliary volume.  For instance, the first auxiliary knob on the first channel of a mixer, controls the amount of volume sent from the first channel to a speaker connected to auxiliary one.  Auxiliaries can also be used to connect external effects, which we will explain later in the external gear chapter.



9- Effects (pre/post fader)

Just like an auxiliary the effects knob is independent to each channel.  When you turn up the effect knob on channel one it is only sending channel one to the effects.  Effects can often have a button that says pre and post.  Pre fader means that the effects are working off the volume at the beginning of the channel strip.  Meaning, when a singer’s vocals are plugged into a channel and we turn down the fx knob, then we press in the pre button next to the fx knob.  At this point we have turned down the effect knob on channel one and we have pressed the pre button.  Now we will lower the channel volume knob / fader located at the bottom of the channel strip.  What will then happen is the vocals being sent to the effects will still be heard, but the main dry vocal sound will be gone.  So we are still hearing the vocals because they are being sent to the fx from before the volume knob, the volume is coming from the gain knob, signifying pre fader.  Pre fader means the volume source is before the volume knob / fader at the bottom of the channel.  Pre fader means that the volume source is coming from the volume set at the gain knob.


10- Pan

The pan knob is a way to move a sound to the left or right speaker.  In a more technical answer, the pan knob allows us to move the sound between the left and right channels of the sound system.  If we move the pan knob to the left on channel one, the vocals will only come out of the left speaker and not the right, because we are panning the vocals on channel one to the left output channel.  The pan knob simply moves a sound source between the left and right speakers.


11- Mute

The mute button turns off the channel so that no sound is transmitted to the speakers.

Mutes are can be labeled different ways but have the same function

12- Volume (Fader/Knob)

The volume knob or fader is located at the bottom of the signal chain.  This controls the volume sent to the speakers.  Remember the gain knob at the top of the channel is different from the volume knob at the bottom of the mixer.  The gain knob sets the volume for the channel, the volume knob sets the volume that we hear in the speakers.  

Channel Volume Fader

13- Routing Options (PFL / 1-2)

Routing options refers to mixers that have sub groups.  If your mixer has sub groups then next to the channels volume fader there will be up to 4 buttons.  Each button will say 1-2, then below 3-4, and then the last button will say “main”.  Each of these buttons will send sound from the channel to either sub ground 1-2, 3-4, or the main output.  If these buttons are on your mixer, you will have to press the main button on each channel to hear each channel.  For instance, If the main button is not pressed then the sound from channel one will not go through the main speakers connected to the mixer.  Sub groups can be used several different ways, the chapter over sub groups will go into further detail.


In Summary to the Channel Strip Definition…

So now we know what a channel strip is and we know what every component on a channel strip does.  Now we can explain that a mixer is simply one channel strip duplicated horizontally.  Each channel are the same components, everything from the mic input to the volume fader.




Two more types of channel strip structure Found on a mixer

Explaining Different Types of Channels on a Mixer

-Now we know what a basic channel strip is, this will make it easy to explain the other two of channel strip designs.  

Stereo Input Channel Strip

  1. Stereo channels
    1. Have 2 ¼ inputs, one on top of the other.  
    2. If the stereo channels start after mic input channel 4, then the stereo channel will be labeled channel 5 and 6.  
    3. Since the stereo channel is meant for an instrument that is stereo like a piano.  The channel label 5 and 6 will also have a label on it that says left and right.
    4. Channel 5 is left and channel 6 is right.  This means that when you plug in a piano’s left and right output into the mixer’s channels 5 and 6.  The piano will play across both main speakers.  The benefit of this is that when a piano player plays on the left side of the piano the sound will mainly come out of the left main speaker.  When a piano is plugged into a stereo channel the piano is able to pan across the left and right speaker.
  2. Stereo Return Channels
    1. A stereo return is similar to the stereo channel but meant for external effects.
    2. The way to use stereo return channels will be more clearly defined in the external effects chapter.


Mixer Output Channel Strip Layout– The rest of the Mixer

Now that we know that the general makeup of a mixer is a few microphone channels duplicated, then a couple of stereo channels, and finally a stereo return.  The next part of a mixer is focusing on outputs and a few auxiliary / effects parameters.  


Main Outputs Found on a Mixer

The main outputs on a passive mixer come in two forms,

  1. XLR Outputs-
    1. Use an XLR cable to connect to speaker / amp
  2. ¼ TRS Outputs-
    1. Often used either a ¼ TRS to TRS cable to connect to speaker / amp
    2. Recommend to use ¼ TRS to XLR male to connect to speaker / amp


Auxiliary Outputs on a Mixer

Aux outputs are either labeled,

  1. Aux Send
  2. Monitor / Mon Send
    1. When an aux send is labeled mon or monitor send, it is because the manufacturer expects the user to connect what is called a Monitor Speaker.  
      1. A monitor is a speaker placed on the stage, which is pointed towards the singer or musician, and it is used for the musician or singer to hear themselves.

Auxiliary outputs are generally ¼ TRS outputs.  The auxiliary output is generally used for monitor speakers which are used by musicians and singers to hear themselves on stage.  Aux outputs use the following.


Aux Output List

  1. Aux output uses ¼ TRS cable
  2. A ¼ TRS to TRS cable can be used to connect to speakers / amps / external gear
  3. Recommend to use TRS to XLR Male cable to connect to speaker / amp / external gear
  4. An Aux is used to connect a monitor speaker
    1. A monitor is a speaker placed on the stage, which is pointed towards the singer or musician, and it is used for the musician or singer to hear themselves.
  5. An aux can be used to send audio to anything.
    1. Recorders, speakers, other rooms for audio, etc…


Auxiliary Send Master Knobs

Each aux send has a master knob found on the far right of the mixer.  The master aux knobs control the amount of overall volume from all channels that is sent to a speaker.  In other words, the “master aux knob one” is what controls the overall volume of every channel that has turned up the first auxiliary knob, the “master aux knob one” controls the overall volume of every channel that is sent to the speaker that is connected to the mixer output “aux send one”.  

Aux master knobs should simply be set at one volume which is generally in the middle, once the master aux knob is set in the middle, each individual channel can be easily added to a monitor speaker connected to an auxiliary output.

Effects Send Master Knobs

Effects sends master knobs are used to control the overall volume of each individual channels fx send.  This is just like the aux send except the fx send knob sends sound to an effect that comes out of an fx return channel.

  1. Fx Return
    1. Is a fader on the mixer that must be turned up to hear the overall effect.  
    2. This helps control the amount of overall effect in the mix
    3. Helps make sure not to have an overwhelming amount of fx
    4. Keeps everything clear and easy to hear.  


Effects to Monitor / Aux

Next to the Aux or Fx Master knobs there is usually an fx to aux knob.  This knob allows the engineer to add effects to the monitor so that the singer or musician can have a little bit of extra inspiration to perform help add to the performance.  


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