Designer Craig French says:

Here is a circuit I designed, I call it the “Fullerwell”. It’s an 18 watt amp, basically a 5E3 preamp with cathodyne phase inverter mated to a Marshall model 1974 power amp. Built it in a 1×12 with a Jensen P12R but I’m sure a greenback would sound good too.

Here is the play video followed by the technology/build video using the Adafruit Perma-Proto board.

In the slides there are a few insignificant errata, here are a few I know of and I’d appreciate it if anyone spots something that looks off just let me know, thanks in advance.
Errata:
1) slides 5&6, I didn’t have all of the necessary KiCad libraries so some of the switches may look odd or oddly wired in this schematic, just refer to the wiring diagrams, those are correct for the switches.
2) slides 5&6, same as previous for the transformers — they may look funny here because I cobbled them together from other transformer symbols in KiCad. I used the Heyboers listed on slides 8 and 16.
3) slides 5&6, same as previous for the rectifier tube. I used 6CA4 (EZ81) as listed on slide 9.
4) slide 19, R7 is listed as the PI tail load BUT R7 is actually the PI bias resistor.
5) slide 19, R18 is listed as “V2 Master Volume Leak” but there is no such thing, R18 is the PI tail load resistor.
6) slide 21, these photos were taken prior to some modifications I later made, slides 22 and 23 include the modifications (added a jumper on the B+ bus, the red wire; modified high side of R24, originally had it soldered before both voltage dropping resistors but it needed to be between them, so that’s why there is a black jumper wire in there now).