PWM Compressors

 In TSM Studio Blog
  • An older, and oftentimes overlooked technology typically used in vintage-style dynamic processors is the PWM (Pulse Width Modulation) constructed compressor. PWM is a gain-reduction technology that has been revived and implemented into modern electronics to transparently control dynamics without residual artifacts that are commonly associated with VCA compressors.
  • To understand how pulse width modulators function, it’s first necessary to understand that each and every time a parameter is changed on a compressor, control voltage changes. Pulse width modulators act as an inherent switch that turns off whenever a signal overloads. Comparative compressors, such as the VCA compressor, lacks the ability to perfectly isolate the harmonic distortion from the primary, compressed signal. When using a VCA compressor, you’re essentially hearing a blend of the compressed signal with altering levels of distortion dependent on how hard the compressor is being driven. On the contrary, a PWM compressor contains an on/off switch that is able to alternate between the two settings extremely fast (on and off in less than one nanosecond).
  • You may be curious as to how the width of the pulse changes are determined. The concise answer is that it’s entirely dependent on a change in control voltage that occurs whenever a parameter on the compressor is adjusted. Simply put, whenever a knob is adjusted on a compressor, the pulse width will either widen or narrow.
  • Because of a PWM compressor’s ability to switch on and off at an inaudible rate, they’re typically described as “cleaner” sounding than VCA compressors with applications that often assure minimal coloring will be applied to the output signal.
  • Examples of PWM compressors include:
    • Pye Compressor
    • Crane Song STC-8
    • Great River PWM-501
    • Sknote Leso Stereo
    • ART Dual Limiter