

(click on photos for larger image)
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.