I quickly surmised that the dying battery was the cause and kept playing until the battery was killed. It sounded like an Atari with emphysema towards the end, but for a few minutes I got a great, unique sound that my other fuzzboxes couldn't come close to. I then used one of those multi-voltage adapters from Rat Shack and pinpointed the voltage at which the fuzz is born. Once in half-dead emulation mode, the Threshold knob functions more like the Distortion knob on a fuzzbox. There is still some sustain added too.
Volume is pretty much the same as regular.
Bought it used nearly a year ago. Volume pot date code says 1979. Now I always am surprised to hear the fuzz that this thing barfs. Therefore, my overall rating reflects the unintended use of the Soul Preacher. 8 Has volume and threshhold knobs plus treble boost switch.