Anyone recommend a neutral tube amp?

The reason tubes are accused of being 'warm' is that they more closely follow the rules of human hearing than do transistors. If neutrality is your goal, and on top of that listenability, due to the constraints of the technology tubes are the only game in town.

Some important rules of human hearing are:
1)Loud sounds mask quiet sounds
2)loudness is detected by the level of odd-ordered harmonics
3)speed can invoke emotional response, slowness often invokes intellectual response
4)ears hear on a logarithmic scale, thus 'decibels'
5)bandwidth is roughly 20Hz to 20KHz.
6)sound location is detected by phase and time

a couple of examples:
Distortion masks detail, which is why SETs can sound more transparent and detailed than a transistor amp (if the speaker is efficient enough to take advantage of the low-power range of an SET).

Getting rid of negative feedback can reduce harshness (rule #2 above). Nelson Pass has shown this in his 'First Watt' amps, and tube guys have known this for a long time.

While no amplifier will ever be 'perfect', the more the rules of human hearing are obeyed the more the result will be an amplifier that is the most neutral while simultaneously being the most musical.

Eagleman6722, could you clarify what you are trying to say?

FWIW the idea that tubes color the sound has the same merit as the idea that transistors color the sound. What colors the sound is anything to do with audio reproduction- IOW it is not a tube/transistor thing...

Hi Detlof, got it!

I play in a couple of bands and I know what you mean there. But as a designer, I do exactly the opposite of what I do in the band. IOW, I try to make the equipment do as little messing with the signal as possible.

Eagleman6722, if you look in the DIY forums, you will see that people are commonly swapping op-amp chips out in their equipment and projects because certain ICs have a 'sound' they are looking for or trying to reduce. This is not a tube/transistor thing, its simply a component thing.

IOW you can no more say a tube amp has the character of certain tubes than you can say that a transistor amp has the character of certain transistors (or ICs.). The only thing is, in tube amps, they are a hell of a lot easier to change :)