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Brickwall Peak Limiting in the Analog Domain

The PL-2 Analog Peak Limiter features:

  • JFET (hard) or MOSFET (soft) peak limiting modes
  • Two independent channels with stereo link
  • Precise readout of peak reduction
  • Stepped input and output controls - ideal for mastering or session recall
  • Limiter circuit out of the signal path when below threshold
  • Transformerless Class A solid-state design

   The PL-2 is a stand-alone two channel version of the very popular peak limiter in our Quartet II Tube Recording Channel. It uses a novel approach to brickwall limiting in the analog domain, one that is fast enough to prevent digital overs without using time delay or phase-shift delay techniques. This allows us to keep the analog signal path short, and keep the limiting circuit 'switched out' of the signal path below the peak limiting threshold. Distortion for all levels below the the limiting threshold is low, and does not rise as the threshold for limiting is approached. Unlike analog peak clippers, which chop off the top and bottom of the waveform, our limiter retains dynamic information at the top of the peak.

   The PL-2 has two modes of peak limiting, using either junction field-effect transistors (JFET) or metal-oxide semiconductor field effect transistors (MOSFET) as the control elements. While both are equally capable of brickwall limiting, each type has its own characteristic sound. The JFET tends to be a stiffer, harder mode of limiting, while the MOSFET has a softer, more compliant response. The resulting waveforms look different, and each device has its own characteristic sound.

   In addition, Input and Output gain controls allow the user to scale the gain structure for a wide range of applications, from driving the front end of an A/D converter at +22 dBu, to inserting it as an effect into a +4 dBu patch bay. Several units can be linked for multi-channel applications.

   Each channel also has an expanded 13 segment LED display which accurately indicates peak reduction.