Hi there, I’ve now listened and analyzed countless 12au7’s (and it’s equivalents) and thought I’d give my opinion on my current favorites.
1st Place Tie: Mazda 6189 Silver Plates 3-Mica and 50’s Valvo Long Plate Angled Getter
*these are somewhat similar to me in that they both have soaring/sparkling top-ends and beautiful midrange. Both have lots of detail. I think Mazda has better bass and is slightly more precise, forward and transparent. But Mazda is also more dry. Valvo is sexier and easier on the ears. To me, the Valvos are a bit light on the bass. Mazdas have maybe a larger soundstage, but Valvo is deeper and more intimate. Tie for first. If someone put a gun to my head, I’d choose the Valvos.