Best 12AU7 Type Tubes for a Preamp

Just be careful who you buy from.   There is a dwindling supply of NOS 

I recently  bought a quad of early 50's RCA 12ax7 and 12au7 and they were not cheap.   Exactly as advertised,  they are true NOS  and test high.  

I recently bought a tube tester , those tubes were exactly as described but I learned that several tubes that were "NOS"  simply were not 

New production tubes were not exactly all that great. Some triodes were so far apart from being matched they are useless .   

Now nothing goes in my gear until I fully test and confirm they are strong and tightly matched 

New JJ gold pin 12au7 are very good.  

The prices you list for two of the three nos tubes is excessive.

The RCA cleartops shouldn’t be $40 each.

The Mullards go for around $175 a pair, unless they are the m8136 variant. Then they’re around $250 a pair.

If you can find a strong tested pair of the Amperex 7316’s (the earlier the better) for $150 each, I’d get those in a heartbeat. 

I've already expressed my preference for NOS tubes and to buy from a reputable dealer, but I must give props to Psvane. My preamp came with a Psvane 12AU7-S with gold pins and it had very nice tonal qualities. It presented a wide soundstage, but lacked the depth that so many NOS have. Nice top-end, not etched like some of the Russians, just a pleasant sounding tube that works very well when combined with NOS.

the PSVANE ART-S series are pretty tough to beat sonically.

If you are looking for more midrange warmth, the RCA black plates are a great choice. 

Brimar CV4003 from Upscale worked great in my Rogue RP-1 and RP-5.
The RCA were brighter.
Genalex Gold Lion we’re pretty good as well.