I posted a new page on power output stages with a headphone focus (though it can be applied to speakers as well). My aim is to eventually try all the variants. Between the Estudiante MOSFET hybrid, Papa Rusa parafeed SE, Bad Hombre differential, and Luciernaga series-feed SE, I’m part way there. Been working on ideas for an all-tube OTL lately. Hopefully I’ll tick that box soon!