Look Ahead; Expander - RME Audio ADI-96 PRO User Manual

9.8 Look Ahead

9.81 Expander

When set to Fast the Expander has a very fast attack time of less than 1 ms. However such a
low reaction time already leads to a smoother sound when processing percussive signals with
strong attack noises (click). The smoothing depends on the actual Gain Reduction. With high
Gain Reduction the Expander needs a longer time to open (between 0.1 and 1.5 ms). A faster
reaction of the Expander is not possible, as it will cause clicks and pops.
The damping on the beginning of the signal can easily be avoided by delaying the audio signal,
but not the control signal. With this the Expander will open although the audio signal isn't pre-
sent yet. This method of processing with a preview is called Look Ahead.
The ADI-96 PRO has no extra switch to activate the Look Ahead mode. As Look Ahead
requires a delay of the audio signal we found it both logical and easy to use when Look Ahead
is simply activated by the already implemented function Delay. As soon as the Delay is acti-
vated and the delay time is at least 0,1 ms the Expander will work in Look Ahead mode. Please
note that the above problem can only be adressed by a minimum delay time of at least 1,5 ms.
Wheter the chosen delay time is sufficient or not can easily be checked by using the function
Bypass DSP.
When set to Slow the attack time is 25 ms. This is necessary to avoid a reaction (an opening)
on very short noises like cracks and clicks, for example when digitizing LP's. The long attack
time can again easily be compensated by a delay of 25 ms, so there is no loss of sound on
material which starts without any fade in.
G
The usage of Look Ahead leads to a delay of the digitized signal, which might be a serious
problem in recording situations where realtime behaviour is required. Please note that the
function EXP was optimized to give excellent results even without Look Ahead.
User's Guide ADI-96 PRO © RME
21