I've been playing my bass in passive mode lately, and really enjoying the sound.
The preamp in the bass is no slouch - a Nordstrand 3B; I like that the Nordy's EQ is flat at center detent, and there's no gain boost unless you dial one in.
It's been my favorite pre in this bass so far; the bass came with a Bartolini NTMB-F, then I installed a Bart TBIBT, then a Darkglass Tone Capsule, and now the Nordy.
I think I keep trying stuff out because the buffering and impedance change from every preamp I've tried so far alters the tonal profile in a way that I'm not liking. And when I think about it, the dual-buffered signal chain of the TBIBT was the one that moved the bass farthest from my preference.
Are there any preamps that truly sound the same flat as the bass sounds passive?
Right now I'm leaning toward removing the active electronics from the bass and replacing with a passive, bypassable varitone circuit.