Tech 21 Bass Boost Chorus 100% analog Mix, Tone and Level controls for warm, organic sounds. Mix control ranges from 100% dry to 100% wet. Speed and Depth work in conjunction to control their respective functions of the modulation Pre-Delay (Boost Chorus) adds delay to the chorus effect before mixing it back in, achieving a wide range from flange/chorus to regular chorus to chorus/doubler to chorus/doubler. Operable with 9V battery (not included) or optional DC power supply (Tech 21 Model #DC2, contact us for this option)