Heavily modified revebr unit by BJFe, treated by Chris Stelloh.
A couple of the tweaks are from Björn – in particular, the 2k2 resistor
from the source of Q1 to ground. Lowering that value fixes a volume drop
that can happen when the 50k dwell pot is maxed. I replaced the second
dwell pot with a 10 ohm fixed resistor, so that it is almost at maximum.
I also added a flat-mids BMP tone control and BC337 recovery stage that
sounds really great paired with this circuit. Using a PN3269a in Q2 can
squeal with feedback (a GOOD thing in my world) so dialing in the 10k
output trimpot is a necessary step. It is possible to set it so that it
only howls when the dwell+mix are turned to maximum. The charge pump is
something I redrew from an old tagboard layout. The 555 doubler puts out
30mA of current which this verb circuit needs most of (the schematic
says it draws around 20mA, and that was before I added the extra
transistor) no matter what voltage you are running it at.
