Phono preamp tube rolling.

mulveling-- Those Mullards, despite their lore and hype, have never really found favor for me, either as gain tube in my Rogue ST100, nor here in the Zestos. I paid a fair amount for them, and really wanted to like them, but I suppose my ears and system don’t really need to be fattened up by the Mullards. : ) If I need thickening, the RCA black plate will achieve that, with no compromise on bandwidth.

I am indeed smitten with the Zestos, but it is my first tube phono amp, so I am new at phono tubes. It is just beautiful all around. I got a good deal on it here at Agon and jumped on it. I’m REALLY glad I did. Insert your audiophile cliches here: "veils lifted...." etc. : )

Another great and cheap alternative (NOS) for me was the Sylvania 12at7WA

Sylvania Gold Brand 12AT7WA is a high-frequency twin triode in a small 9-pin miniature glass package. This is a very rare military gold pins version from the 60’s, made in the USA. The 12AT7WA is found in many high fidelity applications, as each triode section in normal use operates as a class A amplifier. This tube is very low in microphonics due to its rugged construction. Sylvania Gold Brand is an extremely high demand vintage tube. Sylvania was a U.S. manufacturer of vacuum tubes, transistors and electrical equipment, formed in 1931. Their vacuum tubes from the 50’s and 60’s (Gold Brand series) are very nice!

pindac, what’s your 6SN7 keepers ? For what preamp ?

Check out Kevin Deal's videos on tube rolling.

I enjoy tube rolling, but there are three 12au7 tubes that I keep in a virtual rotation in no particular order: Mullard, Chelmer, and Telefunken. These three are consistently quieter than a lot of other tubes. 
I have a small collection of 50s, 60s GE, RCA (clear top in particular) that become noisy with ghosting and microphonics after a fairly short number of hours.
Stick with my three recommended brands and you will be rewarded with stellar sound and stone quiet performance. 
My favorite of the three? Tough call, but I really like the Chelmers, and you can't beat the price!