12BZ7 ///12AX7

Try some "used test strong" Telefunken 12ax7 when you get a chance. They’re solid all-rounders, and relatively common on the 2nd hand markets. But favorite 12ax7, by a good margin, has been the Mazda silver/chrome plate. Unfortunately they’re rare and expensive ($350+ a pair), and they have a bit of extra energy up top - so won’t be ideal for systems that need a push towards a relaxed top end.

Also I like those RCA tall black plates pretty well, but think the Mazdas are much better.

@lowrider57 I responded to the Q concering so called ~~Burn In Theory~~ over at my New Kids topic.
There i completely expose that scam and believe my comment is 
verifible , believebale, honest, fair, unbiased.
I put the final, last nail in 
~~The  Snakeoil Coffin* once and for all.
 @ Mulveling
Someone here on audiogon mentioned in a  post, he has tried Teles and Siemens , the Teles he found more on the ~~warm~~~ side, vs the highly detailed Siemens. 
I always go for clean/clean/details. 
I have Siemens AX's / RCA AX's /tall blacks, arriving this week. 
Look or a YT vid upload , late sunday night. 
The Mazada's , chome plates, , I recall havinga  pair, i did not like them at all.

My system now with new added silver sterling to speakerwires (16 individual wires total, = biwire 1 copper + 1 sterling 14 ga silver  = 2 X 8 = 16 insul wires,,,
and the wires are correctly employed = no criss crossing .
+ took out the E188's in the Lite LS9 Jadis clone pre and installed tyhe stock EH 12AT7's and that as well made a futher gain in details, but is more *beefier* sound, not as laid back/quiet,  as the E188's. Prefer the AT's overall. and so the AT's will remain.
My system has made some progess, and will report back on futher mods/critque.
Our goal here is to finda  path to Pure Class A resolution/highest fidelity. 
3 things , no 4 things are required
1) Patience
2) reserachreserachresearch
3) trial and error
4) $$$$$$$$

The Tele ribbed plates aren't as warm as the smooth plates - you may like those better. Surprised you didn't like the Mazdas, but systems change and optimal tube selections can change over time - are you sure they weren't the 5751 silver plates? Those were awful lol. 

Yes 5751, horrible, 
I am bidding on  a pair of Tele, 16 hrs left,,I am winning at $81,,,tubes pulled from a  estate sale, working ociliscope, look NOS 100%, I am at top $, doubt i win. 
Might try in 2 yrs to pick upa  pair.

I have tried Mazda 12AX7( S) silver plate with Sylvania 12BH7(A) in my Rogue Apollo’s upgraded to Darks at factory, actually on Mulveling’s recommendation. I am very pleased with the results. Currently, I am using  Mazda 5751 silver plate 3mica and like them. They sound more revealing, albeit not as quiet as the silver plate 12AX7S. I understand it’s a matter of personal taste, but am I missing something here?