That's interesting, 3d is a term I've used to describe what I strive for in music playback. Something really, physical, present sounding about the instruments I've found through vinyl -> tubes. I listen to guitar based music, I ask myself does this playback sound like I'm at a gig. That's what I strive for. On my system only vinyl (more so with 70's recordings i.e analog), and through some amount of tubes really brings the instruments out in a lifelike way, in my limited experience so far.