Teenage electronics nerd in 1960s. Best friend and I would harvest Buick/Pontiac/Cadillac car radios available from junk yards for a few bucks. The audio sections were push-pull 6V6 with a heavy audio output transformer. To use these in our home "hi-fi" we had to power them on 120VAC. So, we'd build power supplies using power transformers from old Philco/ Zenith radios; these delivered 6.3 VAC for cathode heaters of car radio amp tubes, 5VAC for cathode heaters of the full-wave vacuum tube rectifier, which in turn provided filtered [choke and electrolytic condenser] higher DC voltage ["B+"] to the car radio amp tubes.
The push-pull 6V6 amps put out 12 -20 decent watts that drove our home-built bass-reflex enclosed speakers, using drivers we'd got from Radio Shack, Allied, etc.
Since then, gone thru AR3a, Dynaco amps, McIntosh, K-horns, B&W, Anthem...