FET Compressors

 In TSM Studio Blog
  • In contrast to OPTO and Vari-Mu compressor models, FET compressors offer an extremely quick transient response time, similar to that of a VCA (Voltage Controlled Amplifier).
  • By design, FET (Field Effect Transistor) compressors are solid state. The transistor used in a FET compressor is a semiconductor that can both amplify and attenuate a signal based on the settings dialed in. FET compressors stand out as unique because of how the transistor works with the entirety of the electrical field. The changes in gain are the immediate result of electrical charges and change in voltage. As voltage is increased, the drain circuit’s resistance is lowered. Essentially, this translates simply to:
  • More voltage -> less resistance -> reduction in gain.
  • The signature allure that compels most engineers to use a FET compressor lays in both the color and punch that are a result of the explosive reaction time that is inherent to these models. In fact, the slowest attack time on an FET compressor still reacts faster than most Vari-Mu compressors. FET compressors, namely the 1176, are commonly used for parallel processing to add color with an aggressive edge.
  • FET compressors work incredibly well on an array of sources, namely vocals, bass instruments, electric guitars, and drums. A common practice is to send a signal through a FET compressor solely for the purpose of using the output transformers to achieve saturation rather than to apply any gain-reduction. Driving the input gain is another method of saturating a source signal to increase harmonic content.
  • A useful understanding of the FET compressor goes a long way as its attack and release knobs function differently than most other compressor designs. With attack and release numerical values ranging from 1-7 (left to right), many would assume that turning the knob clockwise would be indicative of a slower attack or release setting, however it’s the opposite. 1 (extreme left) is representative of the slowest setting whereas 7 (extreme right) indicates the fastest setting possible.
  • Examples of FET compressors include:
    • 1176
    • MC77
    • Purple Action
    • Drawmer 1968
    • Daking FET III