I removed my tubed preamp and plugged the balanced interconnects directly from the 2 tube monoblocks directly to an Accuphase CD player with volume control. A weird thing happened. The sound got better, more transparent, deeper and tighter base.
This is exactly what should happen going direct if the output stage is good which most dacs are today, more transparent, deeper and tighter base also more detail and better soundstage placement and depth. And "almost" the same will happen with a passive pre, if the input impedance of the poweramp is >10x higher than the output of the passive pre.
As now there’s no distortion/colorations from the active preamp is in the signal path.
Some systems may need to be masked/soften up, with preamp colorations, because they system may have faults elsewhere that need that masking/softening or rounding up in the bass/midbass.
Cheers George