I'm not getting why tubed digital sources are a bad idea, in general.
Georgehifi mentions added challenges mating with downstream equipment, but are there other reasons?
Surely there are better and worse designs, but people have mentioned numerous well thought of units, including high end ones. (I'd add add Lampizator to the list; I've heard several of their models sounding quite good in a friend's system.) I'm now solid state, but I've had and enjoyed both.
I'm genuinely curious, but barring more information, it seems like a blanket dismissal of tubed digital is hard to maintain.