XTA DC1048 - Manual (Page 46)

Page 46 DC1048 Integrated Audio Management Operator’s Manual
“D-Max” Clip Limiter
The main limitation with traditional dynamics control is the inability of the
processing to react truly instantaneously to the signal. One of the most
significant advantages of digital signal processing over analogue is the ability to
delay the audio signal precisely and without extensive complex hardware. The
entire domain of digital signal processing is based around the combination of
delaying, multiplying, and accumulating numbers (representing samples of audio)
to implement all the filters and dynamics processing we have come to expect
today.
In the case of dynamics processing, being able to delay a signal allows the
processor module to delay the main signal in relation to the sidechain (the signal
being monitored relative to the threshold), so that it can compensate for peaks
prior to the arrival of the main signal.
Consider the situation of a monitor engineer listening to a band perform. Having
no access to dynamics processors, he has had to resort to manually ‘riding the
faders’ in an attempt to keep control of the levels. Should the level of one of the
channels on his desk reach an unacceptably high level, he will turn it down
appropriately.
There is a hidden
sidechain in operation
even in this case. The
main signal path is fed
through the monitor
desk and the gain
controlled by adjusting
the fader.
The sidechain is formed
by the feedback path
between the engineer’s
ears checking the level
and his brain instructing
his hand to turn the fader down if the volume goes over the threshold he has
chosen.
In this case, the delay between the signal actually going over the threshold, the
engineer registering the situation, and then turning the signal down will be in the
order of several hundred milliseconds at best. This will only be true if he is not
distracted – in reality, it may be several seconds before any gain reduction is
imposed on the signal to bring it under control.