PreSonus AudioBox 1818VSL - Manual (Page 90)

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PreSonus AudioBox ™ 1818VSL
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5.5 Digital Effects
5.5.2 Delay
A delay essentially creates an echo, although you can often use
delays to create more complex time-based effects. The source signal
is delayed so that it is heard later than it actually occurred.
Delay Time. Delay time is the time between the source signal and its
echo. The simplest delay effect is a single repeat. A short delay between
30 and 100 ms can be used to create slap-back echo, while longer delay
times produce a more distant echo. Delay times that are too short to
hear as distinct echoes can be used to create thickening effects. Whether
these echoes are timed with the tempo is a matter of stylistic choice.
Variable Feedback. Variable feedback, or regeneration, produces multiple
decaying repeats. Increasing the feedback value increases the number of echoes
as well as the resonance that is created as one echo disappears into another.
5.4.3 Modulation Effects
Chorus
As its name indicates, a Chorus effect creates copies of a single source signal to
artificially create the impression that there is more than one instrument playing,
voice singing, etc. This ensemble effect is created using a series of short, continuously
varying delays that produce slight pitch-shifts and add fullness to a sound.
LFO Speed and Width: The copies are delayed using a low-frequency
oscillator. Some chorus effects allow you to adjust the speed and width
of the waveform being applied to modulate the source signal.
Depth: The depth control affects how much the total delay time changes over
time. As the delay time changes, slight frequency modulations can be heard.
Phase
Phase shifting creates a copy of the source signal and shifts the copy
in time relative to the original signal, creating from 0 to 360 degrees of
phase difference throughout the frequency spectrum. The shifted signal
is blended with the source signal so that you can hear the copy moving in
and out of phase with the original. This creates a characteristic “swoosh.”
Flange
Flanging is a type of phase shifting. It is created by splitting an audio signal into
two identical signals; applying a constantly varying, short delay to one signal; and
mixing it with the unaltered signal. This results in a swept, “swooshy” effect. The
effect was originally created by mixing the outputs of two synchronized tape decks
playing the same material. By pressing a finger against the flange (top) of one
tape reel, the speed of one machine was slowed slightly, creating phase shifts.