The Yacana CMOS Drive is based on the Way Huge Red Llama, the first commercial pedal from Way Huge originally released in 1992.
Jeorge Tripps has not hidden the fact that he was inspired to start building pedals after reading Craig Anderton’s 1978 book Electronics Projects for Musicians. The Red Llama is almost part-for-part identical to the “Tube Sound Fuzz” circuit from this book. The schematic is identical but some of the part values have been tweaked.
The Tube Sound Fuzz circuit actually dates back even earlier. When Craig published it in the February 1977 issue of Guitar Player Magazine, it was the first known usage of a CMOS hex inverter (in this case a CD4049) to generate overdrive tones. Each stage acts as an op-amp in inverting configuration. Unlike op-amps, though, they are very easily overloaded—and also unlike op-amps, they sound fantastic when this happens.
Craig later simplified the circuit for his “Electronic Projects for Musicians” book by dropping the input op-amp stage. This has the effect of making it more sensitive to input impedance and thus a lot more reactive with the guitar’s volume if the pedal is first in the chain.
The Yacana is based on the Red Llama with a gain switch adapted from the EFPM version of the Tube Sound Fuzz. This switch shifts the between two gain modes (which Craig called “Rhythm” and “Lead”) with a third position added in between the two. Otherwise, it allows either version of the circuit to be built, with the default values being for the Red Llama version and alternate values provided for the Tube Sound Fuzz.