Obviously if a DAC has a tube, the tube has nothing to do with digital. It is usually a cathode follower for impedance matching to the device the DAC is feeding and it's there to color the sound to be tube like(otherwise it's colored solid state like).
Tube DACs
For some time I've assumed that tube DACS are meant for direct output to power amps -- in other words, no reason to use a tube DAC if you are running through a tube preamp (unless all components are by same mfr and designed for synergy).
But lately I have seen posts implying some run Brand A tube DAC through brand B tube preamp -- say, Primal Luna 100 to Rogue RP-9. Can't find any prior threads addressing this topic directly.
So, question: am I wrong to suppose that pairing random tube DAC A with random tube preamp B is a bad, or at least a silly idea, absent a known synergy?
S