There is a lot of confusion about matching tubes. It starts with some vendors, especially on eBay, matching tubes by the way they look (visual matching) to matching on multiple electrical parameters at the same time.
There are 4 parameters that could be used to match preamp tubes:
If you find a tube with a getter in the form of a flying saucer, you can ignore any branding on the tube. It’s practically guaranteed that you have a Soviet/Russian made tube. Some of them are great, like EV/DR versions of tubes, but in the majority of cases, they don’t sound good.
Brimar (BRItish Made American Range) was a part of Standard Telephones and Cables Ltd (STC) and was founded in London as International Western Electric in 1883. From 1925 to mid 1980s the company was owned by ITT of the USA.
There is very little information available on how to read Brimar tube codes, but in general, they are one of the easiest to decipher.
The code consists of multiple sections and usually look like: 4G9/980 (4th week of production in July of 1959, tube type 6060)
BTW, if Brimar labeled tube doesn’t have the date code or it has foreign stamped on the tube, it’s not produced by Brimar, but by some other manufacturer. Many Brimar labeled tubes are actually Soviet made.
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.
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.