12AU7 and 12AX7 long black plates vs short black plates. Any difference ?

I choose more dynamic, that's, 12AX7.

Yeah, let's stay with classics

Mazda 12AX7 silver plates ?..Hmm, got to compare them with Mullard long plates one day.

@slaw Were those Sylvania's the Gold Brand Gold pin 3 mica 5751's? If so, I'm surprised but maybe a difference in other components and maybe not the best for your preamp. I found them to be my favorites in my Cary phono preamp. RCA cleartop 5751's were nice too but I found the Sylvanias to be better overall, super clean, clear and dynamic in my system. Tons of factors go into tube characteristics in different gear, that's for sure. 

@inna I think you asked about 12AU7 variants as well? Amperex Bugle Boy long plates were Joe's favorites. I like them but I find them a tad bright in my rig and am more likely to use Sylvania 6189 Gold PIns, I have two micas which are nice, there is a 3 mica version that may be better. I also have quite a few 5814's that I use for 12AU7, Sylvanias are good. 3 micas, gold pin if you can find them but the non gold pins are good, GE 5814's are pretty good, also RCA clear top 12AU7A are good. I've not tried the older Mullards but don't care for the newer ones. . 

goodlistening64

that's an interesting insight. i never thought about how different tubes would react differently to different gains. the more i learn, the less i know

billpete, of course, I asked about both 12AX7 and 12AU7.

@inna Yes, I thought so and is why I passed along my own observations over the last 20 plus years. My main source of info in the beginning was Joe's Tube Lore and I agreed with most of anything that he ever had to say. I was surprised to learn that Joe based all of his opinions on CD listening and I based mine on vinyl listening. Just kind of an interesting sidenote.