G2
Operators Manual
Page 21
Look Ahead Delay – Pre-emptive Action
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
2
. 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.
For an analogue dynamics processor, the situation is much better. Controlling the
gain electronically, and not relying on a human sidechain feedback mechanism, it can
react much more quickly.
2
XTA would like to point out that whilst the
G2
might
‘sound’ male, not all engineers are necessarily male.
Some might well be female, or at least have long hair.
Summary of Contents for G2
Page 1: ......
