What may not be obvious is that modern tube amp designs are an evolutionary branch from 1930's technology, with only a little coming across from the transistor->digital tech tree. The amps of the 40s and 50s were pretty closely based on reference designs that came from RCA and other tube manufacturers.

Modern passive components (resistors, diodes and caps) are made to a far higher tolerance and are better understood, but tubes and transformers are a mixed bag. The older designs were somewhat overbuilt and can be more reliable or have tonal characteristics that are not available in modern parts.

The key diagram is the one that shows the signal path through the amplifier. Input feeds grid, plate feeds next grid, final output is from plate. Everything else is supporting circuitry.

Note that between each stage there's a capacitor in the signal path. That's to block DC. If you want an amp that amplifies DC, each stage has to run at a higher voltage than the previous stage. The plate must be above the grid in voltage. This was a huge headache in tube computers, both analog and digital.

Transistor circuits don't have the increasing voltage problem. Outputs and inputs are in the same voltage range. That's because transistors are current gain devices, not voltage gain devices.

https://www.youtube.com/watch?v=wcBEOcPtlYk

And gone by the time I was old enough to be interested in electronics.

Nonetheless, my curiosity about them remained and I did eventually seek out books to understand how they worked. I have since built perhaps a dozen hi-fi stereo and mono-block tube amplifiers—some from kits, some from scratch. I've built a handful of guitar amps as well (even sold some as kits for a bit). Point to point, tagboard, PCBs…

Anyone that likes to tinker in electronics I recommend they try their hand at at least one tube project (probably an amp of some kind).

for people who have not had much EE education, what is important about triodes and transistors is that they amplify. you can put a signal in (a signal like from a microphone responding to your voice), and put some power in (like from a battery) and these amplifiers can make an output "copy" of the signal which is more powerful/"louder" than the original.

from this basic function, everything that we think of as "electronic" flows. we would still have electric things like light bulbs, heaters, spark plugs, electromagnets, but basically just electric steam punk frankenstein machines, and nothing subtle. Amplifiers are termed "active" electronics; without them, we'd simply have passive electricity.

I didn't read this article because I already know how these things work, and the article looks extremely confusing, and I've already read my fill of explanations that don't explain anything and (not saying this is one of those) I don't want to even risk that again. it is very difficult to find explanations for how transistors work that make any sense at all.

https://www.youtube.com/@FazioElectric

My first real amp was a JCM800 2203 (technically a JMP "Mk 2 master model", which is just a cascaded JMP/Plexi, which Marshall then later re-released as JCM800 when their export deal expired...but I digress), and when I got into modding this website was my first real encounter with easy explained guides of the circuits.

I promise you it does not contain AC when unplugged :)

Just his list of 5E3 mods (Fender Deluxe) is awesome:

https://robrobinette.com/5e3_Modifications.htm

A reversal, which occurs in the vaccum chamber compresses electrodes, tagging battery terminal from the +/- amplifier schema AC electricity is transformed.

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