Lexicon NUVERB - FOR MACINTOSH Manual page 108

Reference
Additional delay added with the PDLY control can increase the initial time gap slightly,
emulating a situation where reverberant pick-up microphones are located much further from
the source than the main microphones. If less than about 30ms of pre-delay is added, this
additional delay can add clarity with some music, but it can also sound unnatural. Large pre-
delays can be useful for slap-echo effects.
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Lexicon