One characteristic of the BEST-sounding 'passive' devices is that they're detailed--they pass all (or nearly all) of the information WITHOUT adding an edge to the sound that some of us think is more detail. For instance, the sounds of live trumpets and trombones when blown hard have an edge to them, and sometimes they're VERY sharp sounding. When heard live and unamplified, you know you're hearing 'detail' without edginess. Less-than-ideal passive (and active, too) components add an edginess to the sound that's unattractive, and too much of it gets ugly quickly. 'Smoothness' is detail without edginess; I love it and it's my principal sonic goal when modifying equipment*. What I call 5-star components and parts are smooth AND detailed--and tonally neutral, too, without losing any of music's essential fundamentals and harmonics.
* I truly am NOT a GEA; I have to work hard at hearing differences that for me are subtle. The GEAs hear and talk about all kinds of differences that I can't hear.
.
* I truly am NOT a GEA; I have to work hard at hearing differences that for me are subtle. The GEAs hear and talk about all kinds of differences that I can't hear.
.