Technical information

McDSP plug-ins
Colin McDowell’s Operational Notes
The basic operation of the ML1 is fairly simple – select the desired maximum
output ceiling, and then the level, or input threshold, at which signal levels
start to be limited. The di erence between the output ceiling and the input
threshold is the maximum amount of signal increase.
The ML1 uses a very small amount of look ahead (just over 1 msec, or about
50 samples at 44.1 kHz) to minimize the distortion that would otherwise occur
from instantaneous limiting. This low latency allows the ML1 to be used on
other instrument busses (drums anyone?) without exceeding the limit of the
automatic delay compensation of Pro Tools. The ML1 can even be used for live
sound – main speaker arrays can be protected and volume maximums can be
easily maintained.
To further optimize signal integrity and sound quality, the ML1 uses three
stages of limiting for optimum signal peak processing. Each audio sample gets
the ‘triple pass’ to insure the  nal output is of the highest quality and does not
exceed user selected maximums.
The other controls in the ML1 – Knee, Mode, and Release – provide unique
and powerful adjustments to the limiter sound itself, or what is referred to
as the ‘limiter e ect’. These controls allow the ML1 to realize a wide variety of
responses making it suitable for any application.
The Knee mode softens the transition between unlimited and limited signals.
While the Knee control will reduce overall loudness as the Knee percentage is
increased, the limiter e ect becomes even more transparent.
The Release control determines how quickly the limiter recovers from a peak
event, stops applying the limiter gain reduction, and returns to a state where
the algorithm is only boosting the signal by the di erence between the output
ceiling and input threshold. What is not always obvious is the use of the
Release control to augment overall loudness and the perceived limiting e ect.
Short release times (less than 20 msec) increase overall loudness. Longer
release times (400 msec and greater) not only decrease overall loudness, but
also minimize the audible limiter e ect.
Applications
Mastering
During the  nal stages of production, a maximum signal level is determined
and then strictly adhered to. Enter the mastering limiter, a device capable of