Can I use my passive preamp with tube amps?

Perhaps he wants his music to sound real, rather than to sound like audio. He did say that he prefers the sound with a passive. Stan's comment is right on the money. The goal used to be called, "straight wire, with gain."

That's tell en um rodman. Hope you found your gold.

The Sonic Euphoria PLC was designed in a shop that ran Antique Sound Labs Hurricane mono amps on practically a daily basis.
So long as the output from your source components will drive the input of the amps to full volume, you'll do just fine.
With the PLC's autoformer based design, it also does not care so much about the length of interconnects that you're running. Of course, keep them to reasonable lengths, no more than is really needed and you'll do just fine.