How I are inclined to look at it's the Echo/Echo+ tubes (FOM 1600 ~ 2200) are reasonable to excellent tubes with a few "high-end" features, as an example they just about often have Superb halo and IA properties as well as genuinely excellent significant gentle resolution specs (~ mid fifties lp/mm Vs mid twenties for lots of gen 3 models IIRC).If y