Lexicon DC-2 - Manual (Page 58)

50
Lexicon
AC-3 Effects and Parameters
SURROUND MIX allows independent adjustment of the level of the sur-
round channels. Many AC-3 encoded soundtracks sound better when
down-mixed to two channels with the surround level increased by approxi-
mately 2-3dB.
VOCAL ENHANCE boosts dialog in the center channel. By targeting
specific frequencies, it can boost only dialog, without raising the entire
center channel level (which would alter the output balance achieved during
calibration).