What is the best phono preamp you have heard?

Best phono preamp and moving coil section I have had is the
moving coil card or input which Levinson put in his preamps.
Lots of adjustments and tons of gain without hum. Plus it
sounded super. I think the sensitivity of the input is
critical to the sound you get: too little and the sound is
dark and not dynamic or even might be peaky; too much and
the overload is prominent on peaks. Close to the Levinson
have been transformers which match the cartridge used; a
hum problem at times, but usually can be worked out with
grounding and careful placement of the transformer.
CEM

I'm a statified Herron owner who gets to hear the seemly top two contenders (the I/O Sig & Lamm) on a regular basis. I never come home after hearing either the Lamm or I/O with preamp envy. I like the no fuss aspect of the Herron's. The Herron's are at their best with current production tubes and are easy on them. IMO, the Herron's are under appreciated in audio land.

Nothing can beat the midrange of the BAT VK-P10SE SUPER PACK.
Yes, not even the Aesthetix IO Signiture. I heard them both.

The phono stage in my Supratek Grange is absolutely breathtaking; best I've ever owned/heard in 42 years of audio.

I think it depends very much on combinations. I do not think that, with many years and spending a lot of unnecessary money (of course, within my own financial means) pursuing the so call "best single" component per se, makes me realize that there is one such component exists but eventually to presume that the whole concept is just simply a business ball game. It is strictly a system dependence. You can have the so called "best Phono" but to a larger extent you have to consider the cartridge/s to go along with it. I feel that there isn't any single best PHONO STAGE to cater for different cartridge/arm/turntable/preamp combinations. If so, we will at least not to receive reviews on components. Even reviewers have to admit that their reference system has to be changed from time to time. More so, with careful notice, it is the combination of the whole system that got to be changed from time to time let alone the speakers. You can't simply find any reviewer to just to stick one best component and allow the rest of the system to evolve. So, I would advise that, with these forums, try to find out the musically satisfied combination of components from others and of which, it fits nicely within your financial capability.