DIYer, so far put together SET tube amp with 6sn7s and 300bs and a 5ar4, edcor hardware. Made a few sets of speakers with my Dad when a kid, but recenly put together a fullrange smallish TL. Have Class D and Ab commercial amps around the house for TV and background but only valve amps for critical listening. Want to build a low power 6as7 set already designed by Suncalc and learned a little about ltspice enough to simulate output and freq response I should get close to. Would like to know more particularly distortion analysis and how to design an amp from the ground up.