1. VCA (Voltage Controlled Amplifier) Compressors
Features:
- Accuracy and Control: They use a voltage controlled amplifier to reduce gain, allowing fast and accurate response.
- Flexibility: They offer a wide range of compression ratios and adjustable attack and release times.
- Transparency: Generally, VCA compressors are more transparent compared to other types, although they may add a slightly colored character depending on the specific design.
Specific Uses:
- Drums and Percussion: Excellent for controlling fast transients, such as on kick drum and snare tracks.
- Mix Bus: Often used on the master bus to provide cohesion and “glue” to the entire mix.
- Rhythm Instruments: Suitable for instruments that require precise control without losing their naturalness.
Example:
- SSL G Series Bus Compressor: Known for its ability to bind a complete mix together with clarity and punch.
2. FET (Field Effect Transistor) Compressors.
Characteristics:
- Fast Response: Field effect transistors provide extremely fast attack and release times.
- Coloration and Character: Add subtle harmonic distortion and coloration that can bring the compressed signal to life.
- Aggressiveness: Capable of more aggressive compression, ideal for more dynamic styles of music.
Specific Uses:
- Vocals: Popular for vocal compression due to their ability to add presence and sparkle.
- Drums and Guitars: Suitable for drum and electric guitar tracks, where fast and characteristic compression is desired.
- Solo Instruments: Useful for highlighting solo instruments in a mix.
Example:
- Urei 1176: An iconic FET compressor known for its distinctive character and versatility.
3. Optical Compressors
Features:
- Smooth and Natural Response: They use a photoelectric cell to control the gain, which provides a smoother and more musical response.
- Warm Coloration: They add a warm, rich coloration due to the nature of the optical components and amplification.
- Automatic Ratio: They often have smoother, less aggressive compression ratios.
Specific Uses:
- Vocals: Excellent for vocals due to their natural, musical response.
- Bass: Used to compress bass, providing a smooth and sustained sound.
- Acoustic Instruments: Ideal for acoustic instruments that require a smooth and musical compression.
Example:
- Teletronix LA-2A: A legendary optical compressor known for its warmth and musical character.
4. Vari-Mu Compressors
Characteristics:
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- Smooth Coloration: They use vacuum tubes for compression, which adds nice harmonic distortion and warmth.
- Non-Linear Response: The compression is non-linear, providing smoother, more musical compression at lower levels and more aggressive compression at higher levels.
- Retro Character: Its sound is often described as “vintage” and “smooth”.
Specific Uses:
- Mastering: Popular in mastering due to its ability to add cohesion and warmth to the final mix.
- Drums and Vocals: Used on drum and vocal tracks to provide a smooth and natural compression.
- Orchestral Instruments: Suitable for orchestral instruments and strings, where subtle and musical compression is desired.
Example:
- Fairchild 670: An iconic vari-mu compressor known for its ability to provide smooth, warm compression.