There is no late 70's Prog

Colosseum and Curved Air are two that come to mind.

If you are into early soft machine, I can recommend the Robert Wyatt biog "Different Every Time".

But I don't follow convention very much. The amplifier I have is a SET that is true, which is kind of a niche in our hobby. But this is a proof of concept piece I bought from the designer, its a one off. It has a pair of op amps as the first gain stage instead of a tube. The designer needed to see ...