How Does an Audio Mixer Work

Audio mixers lie at the heart of any recording. 

Serving as your control center, a mixer is where you plug in different signals, blend them and add in sound effects. It is also responsible for stereo positioning, routing input signals to recorders and EQ.

In lieu of their extreme importance, it only seems wise to know how an audio mixer works. While the tons of knobs on a mixer may overwhelm you, its working mechanism is quite simple to understand.

Let’s dive right in then. 

How Does an Audio Mixer Work?

Simply put, an audio mixer aka a sound mixer combines various audio signals and turns it into a unified, harmonious mix. Each audio signal is from a different source and undergoes processing and modification on individual channels. This process enables an engineer to manage and tweak sound effects, volume and equalization (EQ.) Finally, the combined audio mix is used for recording, monitoring, broadcasting or any other purpose.

This is the basic mechanism of an audio mixer’s functioning. To understand how an audio mixer works in detail, you need to grasp hold of its different components.

• Input Channels
• Preamps
• Equalizers (EQ)
• Faders
• Pan Controls
• Auxiliary Sends
• Routing Options
• Master Section
• Metering
• Outputs

You may have also come across the term ‘digital mixer’ which is basically a type of an audio mixer. Also referred to as a digital mixing console, or audio digital mixer, it mixes and processes audio signals employing digital processing technology.

Digital mixers are frequently used nowadays. If you understand the mechanism of audio mixers, you can easily use digital mixers too. For now, we’ll focus on the working mechanism of an audio mixer.

Input Channels- Where Audio Processing Begins

The inputs and channels aka input channels are the integral components of an audio mixer. Inputs are basically the real-time, physical connections wherein different audio signals arrive in the mixer.

Typically, playback devices, instruments or microphones feed audio signals to a mixer. Now, every input is related to a specific channel on an audio mixer. For every input, there is a dedicated channel. This allows the audio engineers to individually manipulate as well as control different sound sources.

Input channels on audio mixers are the fixed pathways or processing strips responsible for sound control and manipulation.

Within each channel strip lies numerous functions and controls involved in processing and shaping audio signals. The channel strips play an instrumental role in improving the input level of the signal.

Input Gain

It is in charge of adjusting the amplitude or strength of input signals. The input gain is basically supposed to optimize every input signal before it is further amplified or processed. 

When you increase the input gain, you boost the signal level. So naturally, you reduce the signal level by decreasing the input gain. The ideal processing level depends on the intended outcome and equipment including the digital consoles you are using.

Typically, the input gain is set at a level that increases the signal-to-noise ratio. As a result, you get quite a strong audio signal. The mighty signal is then fit for amplification or processing without adding any distortion or unwanted noise in the signal.

Equalization (EQ)

Equalization or better referred to as EQ helps an audio engineer to modify an audio signal’s frequency response. The engineer attenuates or boosts certain frequency bands to achieve the goal. Typically, the EQ control consists of sliders or knows that help adjust different low, mid-level and high frequencies.

Auxiliary Sends

They route a part of an audio channel’s signal to different auxiliary buses for monitor mixing or processing effects. Auxiliary sends supply signals to the effects units lying externally. These include delay or reverb, and create monitor mixers for stage performers.

Pan Control

This control changes and manages an audio signal’s spatial placement within a stereo field. With the pan control, an audio engineer can position the audio signal’s sound source between the right and left speakers.

Routing Options

These determine the way a channel’s signal is dispersed within the audio mixer. This includes sending the signal to main output channels, auxiliary sends or subgroup buses.

Mute and Solo Buttons

These are helpful in silencing or isolating channels to monitor the audio.

Channel Fader

The channel fader in a sound mixer controls a channel’s overall volume which allows the audio specialist to manage and modify the channel’s contribution to the mix.

An audio mixer’s channels offer control and flexibility to mix and process various audio sources at the same time. You can sculpt each source’s sound, and even blend them well with the help of the channel’s controls.

Gain Control and Preamps: Boosting Audio Signals

Preamps form the initial phase of processing signals in a mixer. An audio signal is typically at a very low level when it enters an audio mixer. This is particularly in the case of a microphone which produces quite bleak electrical signals.

A preamp or preamplifier amplifies this signal and brings it to the line level signal which is the benchmark operational level for audio equipment.

On every input channel lies the ‘gain control’ knob. It adjusts the amplification intensity applied to every line input When you turn this knob clockwise, the amplification or gain increases and the level of the input signal increases. Turning it anticlockwise decreases the gain which attenuates the line inputs.

Modifying the gain control helps ensure that every audio signal is optimally sound for processing, and is free from clipping or distortion. Clipping happens when an audio signal’s level surpasses the mixer’s maximum capacity. The resulting sound is unpleasant and distorted.

Fine-tuning the gain control balances the signal level which improves the signal-to-noise ratio. As a result, the audio reproduction is crystal clear and pristine.

Dynamics Processing and EQ: Sculpting the Sound

After an audio signal passes through the preamp phase, the audio signal is then directed towards dynamics processing and EQ. The audio signal is then contoured to attain the desired sonic qualities of the mic level signals.

I have mentioned above what EQ is responsible for. In this stage, the commonly used EQ controls include:

Frequency Bands

Graphic or parametric EQs help adjust the different frequency bands including bass (low), midrange and treble (high) frequencies.

Gain

It controls how much cut or boost a frequency band needs.

Bandwidth (Q)

It regulates the frequency band’s width that is tinkered by EQ. As a result, you can make precise adjustments to widen or narrow that frequency range.

With these controls, you can diminish frequencies as calibrate and fine-tune the audio signal’s tonal balance. The resulting audio signal has presence, warmth and clarity.

Dynamics Processing

This is where an audio signal attains transient characteristics and a dynamic range. The important dynamic processing controls and tools include gates, limiters and compressors. They ensure that the signal has a consistent level, and that the mix comprising all the inputs is free of unwanted artifacts and noise.

The following controls help achieve this goal:

Threshold

It formulates the level required for dynamics processing.

Ratio

It is used to determine the extent of gain reduction required for a signal when it surpasses the threshold.

Attack

It modifies how efficiently the dynamics processing effect interacts after the signal moves beyond the threshold.

Release

The release is responsible to manipulate the dynamics processing effect to disengage if the signal does not meet the threshold.

You can regulate and employ these controls to completely control an audio signal’s dynamics. In consequence, you can control peaks, smooth out the volume fluctuations and enhance the mix’s clarity to turn it into a balanced mix.

Routing and Mixing: Fusing the Sonic Elements

After all the different sound sources have been modulated, they are blended together to produce the desired audio mix. This is the stage wherein you or a sound engineer will mix up and harmonize the numerous audio elements to get the intended sonic outcome.

Faders

The faders come in handy at this stage. The sliding fader controls reside on a mixer’s channel, and are used to adjust a sound source’s volume level.

You can increase or lower each channel’s volume by shifting the faders upwards or downwards, respectively. They are crucial to attain the desired cohesiveness among all the sound sources for multitrack recording.

Pan Controls

The pan controls aka pan pots help establish an audio signal’s spatial placement within the sound field or stereo. You can position various sound sources between the right and left speakers by panning a signal to the right or left. This creates dimensionality and a sense of space in the audio mix.

Pan pots spread the sound sources across the sound field or stereo which improves the audio mix’s spatial realism and stereo imaging.

Routing Options

An audio mixer’s routing controls help you transfer the signals to the diverse destinations within external devices as well as the mixer itself. 

This does include the different options to transmute signals to the auxiliary sends to monitor mix. They may also be sent to subgroup buses for further subgroup mixing, and finally to the primary output channels to monitor mix which produces the ultimate mix.

With the routing options, you get a lot of flexibility in the signal processing and routing. This is helpful in combining signals so you can fashion intricate mixes with numerous effects and layers.

Auxiliary Sends

They enable you to send an audio signal’s portion from every individual channel and instrument sound to the corresponding auxiliary buses for monitor mixing or processing the effects.

Accordingly, you can apply different effects like delay, chorus or reverb to the separate channels, or even channel groups. This step elevates the mix’s depth and sonic texture.

Using the auxiliary sends, you can fashion individual monitor mixes for the stage performers, and can ensure complete monitoring during a live performance.

Subgroup Buses

With the subgroup buses, you can combine various channels and multiple audio signals to convert them into a combined unit. This step is beneficial in subgroup mixing wherein numerous channels like the background vocals or drum mics can be grouped and processed as a whole.

You get seamless control over different channels at the same time with the subgroup buses. As a result, you can apply EQ, compression or processing to the group as one unit instead of working on each channel and input section individually.

Monitoring and Output: Where the Mix Comes to Life

This is the final phase of the entire audio mixing process. This is where the mixed signal is sent to the master output segment to prepare it for playback as well as monitoring.

With this step, you can assess a mix’s quality before finalizing it, and then sending it to the desired audience.

Master Output Section

This is the portion wherein you consolidate the signal mix. It contains controls that allow you to regulate the mix’s overall volume. These include the volume knobs and the master faders.

It may also comprise level indicators or meters that give you the signal levels’ visual representation. You can check whether or not the mix is within the suitable limits. 

Monitoring Options

You can monitor your audio mix in a recording studio using the headphones or studio monitors attached to the mixer’s primary output channels. 

With the studio monitors similar to monitor speakers, you get a comprehensive and authentic sound reproduction. You can also hear any imperfections or the detailed sound nuances in the mix with the main speakers. 

On the other hand, you get a more secluded listening environment with the headphones. This allows you to critically evaluate the mix and live sound without any distractions from the external environment.

Final Adjustments

When monitoring the mix, you carefully listen to the mix, and make any final improvements if the need be.

You can fine-tune the volume level of every element individually. Moreover, you can adjust the EQ settings, and apply dynamic processing to upgrade the mix’s clarity and balance. 

Basically, your objective is to ascertain that the output level of the mix fulfills the specific sonic requirements, and is consistent across the diverse playback systems.

Recording and Broadcasting

Apart from monitoring, the mixer also has fixed output for broadcasting and recording the ultimate mix.

With these outputs, you or a sound engineer can capture the final mix to archive it, or send it to the desired audience for streaming and broadcasting platforms.

The recording outputs generally link up to the outer recording devices including tape machine or digital audio workstations (DAWS.) On the other hand, the broadcasting outputs often interface with television networks, online streaming options or radio stations.

Well, that’s primarily how mixers work and allow you to carry out sound check.

Wrapping Up

An audio mixer is an essential tool to produce audios as well as shape, blend and create a sense of balance in different sound sources. As a result, you get a polished and refined mix. 

Once you properly comprehend its functions and components, you can unlock its full potential. You then have the ability to generate professional-grade audio content to better hook your audiences to your podcasts and audio works.

Frequently Asked Questions