Know the types of compressors and how they work.
Table of Contents
Did you know that there are different types of audio compressor? Get to know each one of them and learn how they work
Optical
These use an optical isolator circuit formed by a lamp or LED and a photocell. The light source shines more or less depending on the input level. The photoelectric cell reads the varying brightness of the light source and changes gain accordingly. Optical compressor response time is slower than other types, with a smooth attack that can be almost unnoticeable. A good example of this type of compressor is the “Shadow Hills Mastering Compressor“.
VCA
Probably the most common type of compressor is the VCA (Voltage Controlled Amplifier). These are super versatile. A VCA compressor uses an integrated circuit (IC) to give precise control over gain reduction. These generally don’t “color” the sound much, and have very little distortion making them one of the most popular types of compressors on the market. Example: Vertigo VSC-2 Quad Discrete.
FET
These use transistors to vary the gain. FET compressors use transistors to more reliably emulate tubes. They tend to have a unique, fast, clean sound. There aren’t really that many of them, due to the extra circuit required. Example: Universal Audio 1176.
Valve
Most tube compressors are based on one of the circuits above, with one or two tubes in the signal path, for a warmer sound, or colorful as we call it. Example: Manley – STEREO VARIABLE MU
Multi-Band
A multiband compressor is exactly what it sounds like, a compressor that works differently in different frequency ranges. This allows more or less compression to be done on the low frequencies than on the highs or vice versa. The advantage is that the Atack, Release and Ratio for example can be adjusted completely differently, reducing or increasing the amount of compression in each frequency range. They work by splitting the input across multiple filters. Each signal is then passed through its own compressor then recombined (mixed) at the end. In this case, we have at least 2 compressors working at the same time. These, mostly found in DAWs in the form of plug-ins, are uncommon in Hardware, the famous analog world. Example: TUBE-TECH SMC 2B
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