Universal Audio 2-1176 Dual 1176LN - Manual (Page 23)

The Technical Stuff
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maximum value. At very high ratios of 20:1 or greater (some limiters even offer a theoretical infinite
ratio of Infinity:1), “brick wall” limiting kicks in—that is, almost any change in input, no matter how
great, results in virtually no increase in output level. Note that the 2-1176 has been designed so that
selecting higher ratios also raises the threshold level.
As an aside, an expander is the opposite of a compressor: a device that increases the dynamic range
of a signal. For example, a 10 dB change in the input signal might result in a 20 dB change in the
output signal, thus “expanding” the dynamic range.
Knee
A compressor's knee determines whether the device will reach maximum gain reduction quickly or
slowly. A gradual transition (“soft knee”) from no response to full gain reduction will provide a gentler,
smoother sound, while a more rapid transition (“hard knee”) will give an abrupt “slam” to the signal.
The 2-1176 utilizes soft knee compression and limiting, which is generally preferred for most musical
applications; hard knee compression or limiting is more often used in applications where
instrumentation (such as broadcast transmitter towers) must be protected from transient signal
overloads.
Attack and Release
The main key to the sonic imprint of any limiter or compressor lies in its attack and release times;
these are the parameters which most affect how “tight” or how “open” the sound will be after gain
reduction. The attack time describes the amount of time it takes the limiter/compressor circuitry to
react to and reduce the gain of the incoming signal, usually given in thousandths of a second
(milliseconds) or even millionths of a second (microseconds). A fast attack kicks in almost
immediately and catches transient signals of very brief duration (such as the beater hit of a kick drum
or the pluck of a string), reducing their level and thus “softening” the sound. A slow attack time allows
transients to pass through unscathed before compression begins on the rest of the signal.
The release time is the time it takes for the signal to then return to its initial (pre-compressed) level. If
the release time is too short, “pumping” and “breathing” artifacts can occur, due to the rapid rise of
background noise as the gain is restored. If the release time is too long, however, a loud section of the
program may cause gain reduction that persists through a soft section, making the soft section
inaudible.
In the 2-1176, both the attack and release times are user-selectable and are independently set for
each channel. Attack time can be set to between 20 microseconds and 800 microseconds (these are
among the fastest attack times offered by any analog compressor), while release time can be set to
between 50 milliseconds and 1100 milliseconds (1.1 seconds). Unlike many other devices, however,
the 2-1176 attack and release times get faster, not slower, as their corresponding knobs are turned up
(clockwise).