Conclusions
Some of these tubes really catch your attention and make you want to listen to more. The Hitachi is a good
example. Japanese versions of N. American tubes don’t have a great reputation but these are very dynamic and
exciting to listen to. The overall balance and effortless smoothness of the 12SX7s and older RCA 6SN7GTs is
quite noticeable. I liked the Russian red base versions but not the black base ones. The former had the best
detail resolution of all the tubes tried. We would have liked to try some Sylvania and some RCA JAN but the
pairs on hand were not perfect matches so we passed. There are so many physical variants of these tube types
that two tubes coming from what look like identical boxes of the same vintage are often entirely different in
appearance, some differing in overall height (glass pinch vs glass button construction), base height, and
orientation of the two triode structures. If you want to try the Hitachi 12SN7GTs, several suppliers are currently
offering these at very reasonable prices. The Hit-Ray brand is identical.