Valve amplifiers made easy

Valve (or tube, depending on your locale) amplifiers are deceptively simple. There's only a couple components required for amplification from a line level signal into speaker level and impedance. A preamp and a buffer is often sufficient, with simple RC coupling between input stage(s) and the output coupled with a transformer. A handful of components per channel of easy listening audio. The components are inexpensive these days, too, allowing for a full amp to be put together for far less than it would take to emulate a similar sound (single-ended, no nfb) in semiconductor components. If that's the sound being sought, there's little idea in using anything except valve parts to get there except for large scale manufacture.