since building the mutron V, I've been on kind of an envelope pedal building binge lately. after the mutron V, I built a mutron III and I love it, but on that one, i'm going omit the HP and BP settings since I use it with a bass. i'm also planning adding a sensitivity control once I figure it out, so it's not boxed yet.
I did also build and complete a Lovetone Meatball. it was a wiring nightmare with 6 pots and 4 rotary switches but I still managed to fit it into a 1590BB. IMO, it's an awesome sounding envelope filter for bass or guitar. I did add one mod to it which is a 'moog filter' switch that changes the q of the low end in the filter sweep.
here's a couple of pics of it: