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 1176LN 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 which
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 1176LN 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 1176LN, both the attack and release times are user-selectable. 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 1176LN attack and release times
get faster, not slower, as their corresponding knobs are turned up (clockwise).
