The Callisto MKII is a fully analog bucket brigade chorus built around an MN3007 BBD chip — the same type of chip used in the classic chorus pedals of the late '70s and early '80s. The MKII adds a Feedback control that wasn't on the original, and that control is where things get interesting.

The Mix knob goes from standard chorus at noon to full pitch vibrato at maximum — a warbling, tape-like effect that's genuinely disorienting in the best way. The Feedback control dumps signal from the BBD output back into the circuit, gradually pushing the sound from clean chorus toward flanger territory without ever quite becoming one. There's a debate that's been going on for forty years about whether Andy Summers on early Police records was using chorus or flanger — the Callisto MKII can get to that exact ambiguous zone and explore both sides of it.

Rate, Depth, Feedback, Mix. True bypass. 9V DC only — running this at anything higher will damage the pedal.