Some fun schematics to "read" are Fender's digital microcontroller adjustable tube amps; basically the modern incarnations of integration of tube technology with solid-state and modern microcontrollers. Last I knew (when I did web dev for them 5-6 years ago), you could download them from their site.

You can find similar circuits from the 1950s-60s Popular Science back-issues on Google Books; that's the time period when hobbyists were transitioning from tube-based stuff to more solid-state and transistor stuff (transistors came down in price enough, plus they were more reliable) - so occasionally, you can find an article on some project combining both technologies.