Compressor Types and Applications

Feb 16 / Max Porcelli
Welcome Back!
Talking about Compressors, let's understand something more.
So, you want to use a compressor.
The question is: Why?

  • Do you need to glue tracks together?
  • Do you need to tame peaks and transients?
  • Or do you need to prevent clipping?
  • Do you need a Transparent Compression or a Compression as an Effect?
  • Do you need to add color with some harmonic saturation?
  • Or do you need to highlight the rhythmic movement?
  • Do you need to increase the attack?
  • Or the sustain of a recording?

Each answer for each question above implies the use of a specific type of compressor rather than another. Some are better for peak limiting, while others are better for adding glue to bus groups or enhancing a track with some warm harmonic distortion. 

So let's now talk about Types of Compressors. 

Compressor Types

Based on the way that Gain Reduction is applied, we can find up to 6 compressor categories:

  • FET
  • VCA
  • Optical
  • Tube Vari-Mu
  • Diode
  • Pulse Width Modulation

Choosing a suitable compressor also implies understanding its functions and designCertain Compressor types are great for some types of applications, while others are for other kinds of applications.

FET Compressor 

This compressor uses a solid-state "Field Effect Transistor" to control gain and tends to have super-fast attack and release times.

It was developed as a faster version of tube-based compressors, and it's the most colorful type of compressor that can bring instruments forward in a mix, giving a lot of intensity, grit, and grime to any track.

Perfect for peak limiting, they are often used for Kicks, Snares, and all Percussive Instruments. The most popular vintage FET compressors are the Urei and the Universal Audio 1176.

Note that, in the 1176, the Attack and Release times are reversed, meaning that a fast attack and release time are achieved by turning the controls completely clockwise. In contrast, slower attack and release time are on the opposite side.

VCA Compressors

This type of compressor uses a "Voltage Control Amplifier" to control the gain.
It can be both smooth or fast and punchy.

Attack and release times range from very slow to very fast, making them easy to use in many situations like peak limiting or bus compression, and it's great for adding punch and excitement.

One of the most popular vintage VCA compressors is the DBX 160, the SSL Bus Compressor, or the API 2500.

Optical Compressor

It is one of the oldest forms of compression, where the gain reduction is triggered by a T4 optical light cell. With a very slow attack time, it is excellent for gentle and sustained compression. It's musical and superb for smoothing out inconsistent levels and fattening sounds.

Many optical compressors are tube-based, which is perfect for adding harmonic distortion to a recording, and program-dependent, meaning the attack and release times change automatically depending on the input signal.

They are primarily used on Vocal and Bass Guitars. 
The Teletronix or Universal Audio LA-2A Leveling Amplifier is a classic example of this type of compressor.

Tube / Vari-Mu 

This tube-based compressor is entirely program dependent, meaning the ratio and attack/release times change depending on the incoming signal. Thus, it doesn't have Ratio control.

Great for gluing instruments together and controlling dynamics, it has a unique tone, and it's primarily used in the Master Fader or Mastering Applications.

The Fairchild 670 and the classic Manley Vari-Mu are some of the most popular Vari-Mu compressors, but in the list, we can also find the newer IGS Tubecore Mastering Compressor.

Diode Bridge Compressors

This type of compressor, as the name would suggest, uses a diode bridge to control gain that adds a unique character thanks to the tremendous harmonic distortion it can give.

It has a very fast attack and release times and is commonly used as a Drum Group or Bus Compressor.

Some of the most popular Diode Compressors are the Neve 33609, the Chandler Limited Zener Limiter, or TG1, and the most recent IGS Zen Limiter.

Pulse Width Modulation (PWM)

Thanks to its wondrous transparency and low distortion, this compressor is commonly used in mastering applications and allows compression and peak limiting simultaneously.

It has very fast attack and release times, and the gain reduction here is triggered by high-frequency pulse signals with "on" and "off" values.

There are not many Pulse Width Modulation Compressors on the market, but some examples are the Great River PWM 501, which is a 500 module, or the glorious Crane Song and STC-8.

Isn't Enough?

The list above is not exhaustive because we can even find other compressors.
Sometimes you may find that a compressor can't control a sound the way you want. There are several other types of dynamics processors, each with its specific job. Let's see other Compressor Types.


make electronic music limiters
Technically, any compressor with a ratio over 10:1 is considered a limiter. If the ratio could also be set to an ∞:1 ratio, then the compressor is considered a "brick-wall limiter," meaning that, if correctly set, it's impossible to clip the audio.

Typically, they are used to increase the overall volume when mastering or to prevent damage to the speakers.

Some good limiters are the
Maselec MPL2 and the Bettermaker Mastering Limiter or the Pendulum PL-2.

Single Band Compressors

How to Make Electronic Music De-Esser
They are specialized compressors like the De-Essers and do exactly what they sound like remove "ess" sounds.

In fact, they're just single-band compressors that focus exclusively on a specific frequency range to remove the sibilance from vocals and overly bright audio.
Glorious hardware to mention here is the Weiss DS1 MK3 or the DBX 520.

Multi-Band Compressors

Multi-Band Compressors - how to make electronic music
Sometimes, a single compressor isn't enough. The multi-band compressors come in if you need to compress each frequency range differentlyIn fact, each band has its threshold ratio and attack/release times. 

Thanks to its flexibility, this compressor is typically used during mastering.
Some of the most popular Multi-band compressors are the Maselec MLA 4, which is also an expander, the IGS Multicore Compressor, or the TubeTech SMC 2B Multi-band Opto Compressor.


GATES - make electronic music
The gate is a particular type of Dynamic Processor.
With the same classic compressor settings, instead of reducing the gain of a signal when it goes over the threshold, the gate mutes it when it falls below the threshold.
That's why the name Gate and we can consider it an on-off compressorThey are typically used to remove noises from a guitar amp or in close microphones on drums.


And finally, we have the expander, which is the opposite of the compressor. When a recording is dynamically poor or a recording is over-compressed, you might need an expander.

In this case, the ratio is reversed and sets the rate of gain increase (not reduction).
For example, if we set the ratio to 1:3, for every 1dB of signal over the threshold, the expander will increase the signal by 3dB.

Belonging to this category, we have again the Maselec MLA-4, which is a tremendous mastering expander.

We have finally covered the different compressor types 
and their general applications
Now, if you want to get deeper with compression, you can look at this post FeedBack and Fast Forward Compressors.

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