First, I've been looking at the Leach class handout and the Yamaha P2100 design. In particular I've already said that I'm really pretty shocked that the amp sounds so good doing so many things we wouldn't do today.
From the Stereophile Carver Challenge - Page 4
I would like to quote:
On the face of it, what Bob Carver pulled off should be impossible. You can't make a silk purse from a sow's ear. What about the audible differences between transistors, capacitors, internal wiring—all the things that we know contribute to the superiority of no-holds barred amplifiers? What about all the things that amplifier designers have learned during the past 20 years, which enable them to build better amplifiers (at whatever price) than have ever been built before? How could all of these things have been factored into the relatively quick and painless transformation of an average amplifier into a world-beater? But, of course, the "factoring-in" was the key to all this.
This is kind of where I started with the Yammies. WHY do they sound so good despite doing a number of things "wrong" compared to today? And why do they spend money on an extra pair of transformer windings to provide extra negative voltage to the cascode differential pair on the inputs?
A very interesting read on circuit memory and the use of the cascode differential pair inputs:
It's all starting to make sense.... just barely.