Can I use my passive preamp with tube amps?

Passive attenuators can be very transparent/faithful to your signal, regardless of amp topography. In addition to the above: Listening satisfaction will depend on the output voltage of the source/sensitivity of your amp. If the source(CDP, DAC, phono pre, etc) isn't putting out enough to drive your amp to adequate SPLs; you won't be happy. Having owned the(most excellent) Placette Passive Linestage, I found that some pressings, recorded/engineered at lower levels, were less than satisfying. Then again- I like my music loud, and most of my collection produced excellent results.

You could but why would you want to?

If you're asking why he'd want to go to tube monoblocks: If you really need an explanation, you wouldn't understand.

In terms of impedance matching, a passive will in most cases work better with tube amps, they are simply easier loads to drive. What is the input sensitivty of you amps? What is the output volatage of the DAC? In all likelyhood, it will be a very good match.

Rodman99999999999999

That was not what I was asking. I was asking why he would want to use a passive preamp.