Rare John Kallas clone. No Velcro, runs on 9v. (Description from John K's website) The Mike Beigel designed vintage Mutrons from Musitronics are highly sought after envelope pedals. I used to own several of them when they came out in the mid 70's so I built this clone of one and then modded for bass use. I did away with the high pass and bandpass settings (since they cut most of the low end from the pedal), made it true bypass,added a sensitivity control, and added a 'Moog' filter switch. The originals are excellent sounding 'auto-wahs' and mine is capable of sounding just like one, only with a little more adjustability.