Pendulum Audio PL-2 Peak Limiter

The Pendulum Audio PL-2 Peak Limiter owns the category of 'peak limiter' and is virtually a requirement for any mastering studio.

The Pendulum Audio PL-2 Analog Peak Limiter is a stand-alone two channel version of the very popular peak limiter in Pendulum Audio's 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.

Pendulum Audio PL-2 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
• Controls:
  • IN/BYPASS Switch: With the switch in the 'IN' position, the peak limiter activated, and the LED near the switch is illuminated. When in 'BYPASS', the PL-2 is entirely out of the signal path.
  • INPUT: The INPUT control is an 11 position stepped switch that increases the gain of the input stage in 1dB increments from 0 (unity) to +10dB.
  • OUTPUT: The OUTPUT control is an 11 position stepped switch that increases the gain from 0 (unity) to +10dB, or decreases the gain from 0 (unity) to -10dB in 2 dB increments.
  • CEILING: The CEILING control determines the signal level at which the peak limiter is activated. It can be set from +22dBu to +10dBu. This encompasses the range of 'digital zero' most often encountered with typical A/D converters, as well as having additional margin for using the peak limiter creatively at lower levels. When the OUPTUT is set at unity gain, the CEILING control indicates the maximum output level.
  • JFET/MOSFET: The JFET/MOSFET switch determines which type of device is doing the peak limiting. The JFET gives a stiffer form of limiting, while the MOSFET is more forgiving. Due to the differing nature of the JFET and MOSFET devices, slight re-adjustment of the CEILING control may be necessary when switching between the two modes.
  • LINK: This switch links the two channels for stereo operation. The IN/BYPASS, CEILING and JFET/MOSFET controls are linked and controlled by Channel 1. The INPUT and OUTPUT controls are not linked and must be set individually.
  • I/O GAIN: With the switch in the 'IN' position, the Input and Output Gain switches for both channels are active. When the switch is OUT, the PL-2 is in unity gain mode and the INPUT and OUTPUT gain stages are completely bypassed. This shortens the signal path (desirable for mastering applications) and calibrates the maximum output level to the value set by the CEILING control.
  • LED Display: The 13 segment LED display gives a true indication of the amount of peak limiting applied to the signal. It displays the amount of peak reduction in 0.5 dB increments from 0 to -4dB, and 1 dB increments from 4 to greater than -8 dB. The LED ladder uses a 3 color scheme to indicate how audible the peak limiting might be on transient source material.
  • Multi-Unit Link: The MASTER OUT and SLAVE IN jacks permit linking several units for multi-channel applications. Connect the MASTER OUT from one unit to the SLAVE IN(s) of all linked units. When all units switched to 'Link', the CEILING control of Channel 1 of the master unit sets the ceiling of all slave units.

Pendulum Audio PL-2 Peak Limiter Specifications

• Circuit Type: Class A solid-state peak limiter with transformerless balanced inputs and outputs and dual-mono or stereo operation
• Input Sensitivity: +4dBu
• Input Impedance: 20k Ohms
• Input Gain: 0 to +10dB in 1dB steps
• Freq. Response: -1.0dB 5Hz and 80kHz
• Noise: >90dB below +4dBu
• Distortion: less than 0.03% THD+N, 20Hz to 20kHz, at all signal levels below limiter threshold
• Output Impedance: 300 ohms
• Output Gain: -10 to +10dB in 2dB steps
• Max. Output Level: +27dBu
• Polarity: input and output XLR connectors are pin 2 hot
• Display: 13 segment LED ladder from 0 to -8dB
• General:
  • Power: 120V or 240Vac, 16W
  • Power Supplies: +± 18Vdc, +15Vdc, +12Vdc, fully regulated
  • Dimensions: 1U enclosure, 19" x 1.75" x 8.0" (48.2 x 4.4 x 20.32 cm)
  • Weight: 6.7 lb. (3.1kg)
  • Note: Operating level is +4dBu = 0VU = 1.228v

Pendulum Audio PL-2 Peak Limiter Includes

• Pendulum Audio PL-2
• IEC Mains Power Cable
• Operating Manual