XTA C2 Operator's Manual

XTA C2 Operator's Manual Manual pdf 21 page image

C2 Operators Manual Page 21Look Ahead Delay – Pre-emptive ActionOne of the most significant advantages of digital signal processing over analogue is theability to delay the audio signal precisely and without extensive complex hardware.The entire domain of digital signal processing is based around the combination ofdelaying, multiplying, and accumulating numbers (representing samples of audio) toimplement 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 processormodule to delay the main signal in relation to the sidechain (the signal beingmonitored relative to the threshold), so that it can compensate for peaks prior to thearrival of the main signal.Consider the situation of a monitor engineer listening to a band perform1. Having noaccess to dynamics processors, he has had to resort to manually ‘riding the faders’ inan attempt to keep control of the levels. Should the level of one of the channels onhis desk reach an unacceptably high level, he will turn it down appropriately.There is a hiddensidechain in operationeven in this case. Themain signal path is fedthrough the monitordesk and the gaincontrolled by adjustingthe fader. The sidechainis formed by thefeedback path betweenthe engineer’s earschecking the level and hisbrain instructing his hand to turn the fader down if the volume goes over thethreshold he has chosen.In this case, the delay between the signal actually going over the threshold, theengineer registering the situation, and then turning the signal down will be in theorder of several hundred milliseconds at best. This will only be true if he is notdistracted – in reality, it may be several seconds before any gain reduction is imposedon the signal to bring it under control.For an analogue dynamics processor, the situation is much better. Controlling thegain electronically, and not relying on a human sidechain feedback mechanism, it canreact much more quickly.1 XTA would like to point out that whilst the C2 might‘sound’ male, not all engineers are necessarily male.Some might well be female, or at least have long hair.