The Volcano device is a little one-knob wonder inspired on EQD Erupter, with roots on the all-time classic Fuzz Face.
The people from EQD had a pretty interesting approach on the conception of this fuzz, first of all, their idea of having one single Bias knob, leaving the standard ‘Fuzz’ and ‘Volume’ as it was cranked at 11 as most of guitar players like to use, but having the chance to dial it at taste by controlling how much voltage you are feeding into the transistors by the Bias knob.
Another interesting thing about this pedal is the first section, the buffer, and the pickup simulator. The goal of this is to make this circuit ‘Pedal board friendly’, especially with wahs.
On this circuit we have included two internal trimpots, one acts as a volume to set up the max output you’d like to get out of this box, the other one ‘Bias+’ allows you to do some fine-tuning on the behavior of the main bias knob.
For further analysis on this circuit take a look at this thread on Free Stomp Boxes Forum