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. Â Both have lots of detail. Â I think Mazda has better bass and is slightly more precise, forward and transparent. Â But Mazda is also more dry. Â Valvo is sexier and easier on the ears. Â To me, the Valvos are a bit light on the bass. Â Mazdas have maybe a larger soundstage, but Valvo is deeper and more intimate. Â Tie for first. Â If someone put a gun to my head, I’d choose the Valvos.
Often when I buy or receive old tubes, pins on the tubes are oxidized. Big issue with oxidation is that it prevents pins making good contact with the socket. Because of that in the worst case, tube would appear to be completely dead or it will make strange noises during playback. Fixing this issue is quite simple. Just pray pins with DeoxIt D5, wipe in with a cloth and the problem will be solved in the majority of cases. If that don’t help, sometimes using a small screwdriver and cleaning pins one at a time to remove junk off the metal. They spray with Deoxit again to ensure that what ever is left is dissolved.
There is a lot of discussion about Black vs Gray plates tubes. Some people believe that claim that black plates sound better is just a myth created by tube vendors to increase prices, some people swear by black plates in their systems.