What's the best Tube DAC you have heard?

I loved the Modwright Transporter. With the tubes optimized, it is difficult to imagine it could be bettered without dropping a whole lot more cash. It directly serves your computer-based library as well. If you can find an Audio-GD reference 7 or 8 (no longer available) - They don't have a tube output, but are an outstanding implementation of the PCM1704UK chip, rumored to be discontinued by TI, and one of the last great R2R chips - both DAC's I'm currently using utilize these DAC chips and render a very natural sound. There are other great players and DAC's that utilized this chip as well. If you are looking at tubes for the reasons I assume you are, I'd also consider this direction, in which case you would not really need a tube buffer to cure hyper-detailed digititis because it won't be there if that R2R chip is well implemented. Not that there aren't great delta-sigma options (the Transporter actually uses an AKM delta-sigma chip).

since nobody has specified what "best" means, the implicit connotation is one's favorite dac, regardless of its sound.

in that case, the first zanden dac smokes them all.

since nobody has specified what "best" means, the implicit connotation is one's favorite dac, regardless of its sound.

in that case, the first zanden dac smokes them all.

Regardless of its sound? What else would it be a favorite on the basis of? Its looks, perhaps...construction? I kind of lost you there.

It is reasonable to assume the OP is asking for a personal favorite based upon experience. What qualifies as "best" obviously will differ from person to person depending upon their priorities. In this respect, the best one could hope to come away with is a general idea of what some people prefer, and use that as a point of departure. If one wanted to reference this further one might go back and look at the posting history and or ask questions of the person rendering the opinion, to further discover where their preferences might be similar or disimilar to their own. Your statement, "...the zanden smokes them all," implies that you've heard "them all" in direct comparison to the Zanden. In what respect does it "smoke them all"? And what "all" have you done direct comparisons with, having both DAC's in the same system in the same room, at the same time?

I have been using a VAC DAC 2 Mk 2 for many years----done a lot of A/B with other digital gear---the VAC remains-----I also own an Audio Logic 34 which is very close to the VAC (same person designed both, Jerry Ozment)

Not all of my list has tubes but here are my favs....Museatex Bidat, Audiomeca Enkianthus (1st gen and X model), Camelot Uther Mk 4, Kora Hermes (if modded), Audio Aero Capitole (has digital in, so can be used as a DAC), Check out the TADAC..a real sleeper and very flexible with tube rolling. EAD 9000 Mk 3 (whatever was the last version). The Berkeley is quite good.