I agree with everyone who said most or nearly all tube preamps are SET, but why?
In other words, why is a simple single-ended triode able to give 21st-century state-of-the-art performance in a preamp circuit, while similar performance in the power amp seems to require ultralinear push-pull circuits or something even fancier? Is it just the ability to drive the nasty load characteristics of the average loudspeaker? Just interested in case anyone knows the answer :)