Types Of Compression

What is Compression?

In the simplest terms, these are used to reduce the dynamic range ( the difference between the softest and loudest part of a signal). It helps in achieving an overall higher average loudness levels. ( Hicks, n.d.)

The most basic parameters you can find on a compressor are - attack, release, threshold and ratio.

Now, lets discuss about the types of compression-

1. VCA Compression

VCA stands for Voltage Controlled Amplifier which is a type of mechanism that is found in a lot of musical applications. These have all the basic parameters of a compressor i.e attack, release, threshold, ratio and sometimes knee.

“In the case of a VCA fader on an analog console, the control signal (which is you moving the VCA fader) “tells” all of the tracks in the group to diminish in level by an equal amount. In a VCA compressor, however, signal is split through an IC chip (another semiconductor device) into the detector path (which controls the compression effect) and the output path (which is what you hear).” (Messitte, 2018)

VCA compressors can be found on SSL channel strips & API compressors. Their predictability and repeatability is often loved by many engineers. These can be used on master fader, a group or individual channels like guitars, basses, etc.

Most compressors used voltage controlled amplifiers and it can be confusing to distinguish between a VCA compressor and some other. However, the housed integrated circuit of a VCA compressor helps with the tunable aspects of the compressor with minimum distortion. (Silverstein, 2017)

2. Optical Compression

This special kind of compressor used light dependent resistors. But, let us understand what is a resistor first.

In layman's term, resistance is a hindrance to the path of any entity like electricity, light, etc.

According to Woodford, “if you turn the volume down, you're actually turning up the resistance”.

In optical compressor the light element such as the LED feeds on the audio signal and it informs the compression unit or circuit how quickly to act or compress the audio signal. However, the communication between the light source and resistor is not instantaneous. Different types of light sources lights up at different speeds and the material of the resistor defines how quickly it will react. The attacks and release of an optical compressor is not linear and has a little delay following a logarithmic slope. (Messitte, 2018)

It is ideal to use this compression on vocals, leads in general because it is not that harsh as that of any other compressor.

3. FET Compression

It stands for Field Effect Transistor. Now what is a transistor? It is a semiconductor that can both amplify and attenuate signal in accordance with the settings you dial in.

Sometimes, people confuse FET with VCA compression. However, there is a fundamental difference in the transistors: “In a VCA compressor, the transistor is housed within an integrated circuit (an IC) which responds to the voltage of your incoming signal. The FET, however, works with the electrical field as a whole, and gain changes are the result of electrical charges in addition to voltage.” (Messitte, 2018)

FET compressors are capable of extremely high attack times but adds certain colour to the sound. It can be used on guitars or drums for a great sound.

4. Tube Compression

It is probably one of the oldest types of compression ever. Tube compressor usually have a slower response i.e. attack and release times, as compared to any other type of compressor. Therefore, they tend to add coloration to the input signal and thus provides that vintage sound to it which might be impossible to achieve with any other type of compressor. ( Hicks, n.d.)

References

Hicks M. (n.d.). Audio Compression basics. [Blog Post]. Retrieved from https://www.uaudio.com/blog/audio-compression-basics/

Messitte N.(2018). 4 Types of Analog Compression and why they matter in a digital world. [blog Post]. Retrieved from https://www.izotope.com/en/learn/4-types-of-analog-compression-and-why-they-matter-in-a-digital-world.html

Silverstein D.(2017). What are the different types of compressors? [Blog Post]. Retrieved from https://audiohertz.com/2017/08/07/what-are-the-different-types-of-compressors/

Waves. What Compression Plugin Should I choose for my mix? [Image]. Retrieved from https://www.waves.com/which-compressor-plugin-should-i-choose-for-my-mix

Woodford C. (2019). Resistors. Retrieved from https://www.explainthatstuff.com/resistors.html