http://www.catalinbread.com/karma-suture.html (http://www.catalinbread.com/karma-suture.html)
Catalinbread now have their take on the Harmonic Percolator.
Four controls: Input, Output, Diodes, Density.
What? How? Interesting.
I'm going to guess diodes is a 10K-25K pot in series with the whole diode shebang, and I think the best place for "density," if that's the bass control, would be a cap blend with the 2.2uF cap between the collector of Q1 and the base of Q2. It COULD be the 47uF on their emitters, but the pedal has a tendency to not work when that cap gets too small, so I'm not sure.