I probably said enough about the Crowther Hotcake (and New Zealanders) in the previous post – so I’ll stop now.   Short story – it’s straight op amp clipping with some filtering.   

Although I should say that this has an unusual bypass system – it’s not true bypass, note the switching.  I’ve included a modded layout for standard true bypass switching.    

CROWTHER 1977 HOTCAKE VERO LAYOUT