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Compressors were originally a technical solution to the limitations and constraints of the equipment used in broadcasting and the limitations of the recording mediums.

In radio, in order to make things easier, sound technicians use a “leveling amplifier” to automatically reduce the audio segments that are too intense. This prevents the risk of distortion during signal transmission.

This technological breakthrough in the world of radio gave birth to a classic compressor that is still used today. The LA-2A from Teletronix is highly esteemed by sound technicians.

The dynamics of a symphony orchestra, which can be up to (+/- 100dB), needs to be compressed, i.e. reduced, so that it can be pressed to a vinyl record (+/- 75dB).

Some embrace the versatility of compressors to manipulate a sound source, either surgically or aesthetically, while others take another approach and use them only as a kind of safety net. The compressor is then adjusted only to prevent overloads and unwanted distortion.

Technological evolution and the audacity of some audio technicians (Joe Meek, Bill Putnam) have diversified the creative and technical motivations that have expanded the use of a compressor beyond its original use.

Possible uses:

  • Improving and giving weight to the drums (fattening drum sounds)
  • To increase the natural sound of an acoustic instrument
  • Timbral modifications (e.g., to brighten a sound source and/or give it more presence)
  • Modify the rhythmic expression of a song
4 major types of compressors are widely used in the arsenal of audio technicians:
 

  • Tube compressors

The quality of these compressors is intimately linked to the particularity and degree of maintenance of the tubes they use. They naturally modify the timbre of the sound signal.

The Fairchild 670 contains about twenty tubes in its case and has shaped the sonic identity of Motown and Beatles recordings.

 

  • FET compressors

FET compressors are trying to reproduce the sonic imprint of the tubes with transistors. They are faster and very versatile.

The 1176 (Urei) is probably the most used compressor if we count the original as well as the countless software reproductions. The “all-button mode” (or “british mode”) of the 1176 during parallel compression has no equivalent and the timbre and amplitude of the signal are changed in a unique way.

 

  • Optical compressors

In an optical compressor the louder the sound source, the brighter the light emitter (the bulb). Consequently as the impedance increases the output volume decreases.

The housing of this type of compressor can contain various components apart from the light bulb (the photocell) such as tubes or a VCA. Each model has something unique. The compression can be very transparent or more coloured. Ideal for soft and not overly percussive sounds.

The TUBE-TECH CL 1B and of course the LA-2A (mentioned above) are particularly effective for controlling a voice, acoustic guitar or bass.

 

  • VCA compressors

VCA compressors are also very versatile. This type of compressor made music history when Solid State Logic introduced a VCA compressor in the master section of its SSL 4000 console.

This allowed users to compress their entire mix to both control levels and increase the “glue” effect.

Other VCA compressors that are worth mentioning : 

– The DBX 160 VU  is known for its unique sound character. Manufactured in 1976 and easy to  handle,
– The Vertigo VSC-3 (or VSC-2) Quad Discrete Compressor has built its reputation largely on its four “1979” handcrafted discrete VCAs.
“The Mercedes of VCA Compressors” – VINTAGE KING

The compressor models mentioned in this article can also be used as plugins.

 

Notes : UAD plugins require external DSP cards to work.

If you want native alternatives of equivalent quality (that can be used in the classical way with a simple computer) you can turn to Plugin Alliance or IK Multimedia T-RackS also offering emulations of La-2A, Fairchild, 1176, SSL G Bus Comp, Vertigo VSC-2 and many others …

Any question or comment on this article? Contact the author: Jonathan Doyon.