watercourseRe: passive preamps. I have used TVCs and resistor-based, and indeed, with digital sources, there was a noticeable flatness to the sound. With all of my phono stages
Very simple explanation for this, this is why I never recommend a passive for a preamp just with a TT/phono stage setup, unless the phono stage has a well known strong low impedance output buffer with enough gain.
If this was the case then your phono stages output stage was not up to the task. As many are hardly ever as strong as other non phono stage line sources, such as cdp, dacs, tuners ect
Cheers George