[Amps] where to begin

[Gustavo LU6AGV]

Hello,
I'm a homebrewer ham, and wish to lean (and build) about amps

I have read a lot from internet (KK4DR, ND2X, VK3HZ  and other pages)

I saw lot of circuits & diagrams, even when I have a good Electronics
backgroud (High School Technician) I really don't finish to understand
why some thing are there.

so, do you have any point, link, etc where I can learn about *Design
with valves* ???

ps: I believe that I'll build an amp based in Russian G35B triode.

why: cheap, ¿reliable?, I live really far away (end of world) and
money is a scarce thing by here

thanks in advance

73's
Gustavo
LU6AGV