I need to correct some of my information about Jack Gentul, but the timeline is starting to make sense. One really significant piece of information for now: Jack Gentul designed all but the earliest of the Sano tube amp circuits, and ran the manufacturing side of Sano for just over a decade. So Jack is not only the fountainhead of Hilgen amps, but Sano amps as well.
Not a bad track record.
Will revise Jack Gentul page tomorrow with new information.