the goat generator demo suggests that the auto-clean circuit is still under patent protection, but that seems unlikely at least for anything originally patented in the 19080s. the demo suggests that the "clean" button is just a gain boost (and that may or may not be accurate), but it seems like something truer to the original pedal could have been done there if it made a significant difference in the sound. maybe the overall circuit in the GOAT is quieter than the original and the boost was enough to "clean" it up.