Best small signal tube for a preamp?

e\Each of those tube types, their variants and diff manufacturers will have a different sound. Try looking at Joe's Tube Lore over at Audio Asylum for description of each. FWIW, Joe does not like the sound of almost any 12AT7.

Yeah, I copied Joe's paper a couple of years ago and noted he doesn't even discuss the 12AT7. That is the only tube my CDP uses. He also doesn't like 12AU7, saying - "I would say this is a fairly unexceptional tube family." I found it interesting Andy at Vintage Tube didn't seem to like 6922 tubes, a few years ago when I called him to discuss retubing my SF Line 3SE. Some like 6SN7's in preamps for their "bigger" sound, and I found that true in an A-S MP3. BTW, the Amperex E81CC's sound different, but overall better in the Zoe than the EH 6922, although they do not seem to offer as much gain and they may not be as good as the 6922 at higher volumes. At low/mid volumes they are smoother, richer, more dimensional and maybe quieter, but that may be a function of tube quality and not tube type. Thanks for your thoughts.

I have a Zoe, and have acquired the following tubes thus far:

Sovtek 6H30pi
NOS Mullard 12AU7
NOS Siemens 12AT7 (early '60's)
NOS Sylvania 6BK7B

The Sovtek was warm, smooth and too weighty, and lacked some focus, detail, and dimensionality. I wouldn't say it's accurate.
The Mullard was a fantastic all-rounder. Rich & nice balance, but I was looking for more punch and midrange clarity. I'm now trying the Siemens. It's not yet broken in (20 hours or so). I'm very impressed so far. Very quiet, more 3d, solid bottom, and slightly more air, although w/ some grain and not as rich as Mullard's midrange (maybe after a few more days?). I've not yet tried the 6BK7B. About the others, I'm not sure if 6BZ7 is worth a try (the only one I can find is $8 a pair though), and I've read that the 12BH7 and 6922 are not low in microphonics and were not originally designed for pre-amp use... so I'm leaving them for later.
One odd thing I noticed when changing from 12AU7 to 12AT7 was that I had to turn the volume dial 40% higher with the 12AT7 to achieve similar volume levels. I was under the impression the 12AT7 tube has about 40% more gain than the 12AU7. So shouldn't it mean I should be turning the volume dial down instead? Anyways, I'll let you know when the Siemens has fully broken in.

Also don't forget the Zoe is a phase-inverting pre-amp, so you should reverse the polarity of your speaker cables (on one end) for optimum sound. Cheers.

Are you sure about the phase inversion? I did not know that. I will reverse leads and see what it sounds like. Keep me posted on your tube trials. I am in the process of getting a pair of NOS Amperex 6922's to try.

The manual doesn't say anything about phase inversion, and I don't have testing equipment to be 100% sure, but the Audiogon fellow I bought it from actually tests and writes technical papers for Soundstage magazine, so I'm taking his word for it. I'm very pleased with the Zoe, as it's right at home (center of it really) with the rest of my system, each costing more than Zoe.
I've read that NOS Amperex Bugle Boy 7AU7/7AT7 are some of the best. I'd love to also give Telefunkens a try. Can get used for about 1/2 price, which might be good as they usually have twice the life of others...