I used to think passive preamps were superior to active preamps given right the setup, but

Genes,

"Create your own "neutrality" of sound. One that produces a believable sound that YOU THOROUGHLY ENJOY. Not one we are to be told is enjoyable but does not quite move you. It always has to be quality - low noise - design. That never varies.
C'est la vie."

Sage advice. You're a true philosopher. But there are many in high end who will try to convince you what the "truth" should be and what should be "enjoyable". And they will charge an arm and a leg for it.

"The best preamp is no preamp?... Possibly... but only if the recording was perfect and recorded in an ideal space with phenomenal room acoustics.   Otherwise? I still prefer Technicolor movies over the plain variety. I know.. Not real... But, so much more pleasing and stimulating to your soul. After all, that is why we seek to listen to music! Recording engineers know this. That is why they will often times add effects and enhancements to what was recorded.  

I learned my big lesson when I began op-amp swapping with my high quality pre-amp/phone amp. No piece of equipment is neutral. Even the passive ones. For there are various kinds of passive preamps that produce different sound! So? Create your own "neutrality" of sound. One that produces a believable sound that YOU THOROUGHLY ENJOY.   Not one we are to be told is enjoyable but does not quite move you. It always has to be quality - low noise - design. That never varies. 
 C'est la vie."

+++++++++++++1, Genez !!!!!!!

J. :):):):):):):):)

A typical explanation for why passives sometimes don’t perform as well as actives is that the source doesn’t have enough voltage/current to push the signal through a passive to the amp. I think this was even mentioned by someone in this thread. While that can be true, I submit that this is all too often misunderstood and not the limiting issue.

Regardless of the line source type (CD, DAC, phono stage etc.), that source doesn’t know whether it’s connected to a passive or active preamp. All it "sees" is the impedance it’s driving into. If that impedance gets too low the source’s output stage won’t be strong enough (current capacity) to deliver the voltage signal properly because the current demand is too high (resulting in poor dynamics, flabby bass etc. ).

With active preamps, the source sees only the input impedance of the active preamp - typically 10k or higher. With passive preamps (resistive types like pots, stepped attenuators and LDRs), the source sees the combined impedance of the passive preamp in parallel with the amp.

If the passive has a stand alone input impedance of say 20k and is connected to an amp that also has a 20k input impedance, the combined effective impedance seen by the connected source is 10k. No different that the active in the above example.

If a given passive with a decent inherent input impedance disappoints relative to an active alternative, I would submit it’s not simply because the source can’t deliver the goods.

The related question of impedance matching (sufficient impedance bridging) is the number one topic with passive preamps. What we’ve found in actual practice with our LDR preamps in combination with countless different customer sources and amps is that impedance matching is rarely a limiting factor.

For what it's worth, Emmanual Go, producer of the superb lineup of First Sound tube preamps initially marketed a passive preamp.  Eventually he began to engineer, manufacture, and sell dual mono actives with separate power supplies.  I recently paid Mr. Go to install the two "S" upgrades in my FSPD III and an incredibly quiet, dynamic, and musical preamp jumped yet another notch in performance.  It is the only component I've owned during 45 engaged in this hobby that I've never considered selling.  

Mitch2 6-17-2016 4:59 am EDT
It is not just about gain but I believe also about ... frequency variations with impedance.

This is a good point that warrants additional emphasis, IMO. If the component that is driving a resistive-based passive preamp has an output impedance that is essentially constant over the frequency range, and if the component that is being driven by the passive preamp has an input impedance that is also essentially constant over the frequency range, then what might otherwise be an impedance incompatibility will simply result in a slight reduction in gain (putting cable effects aside, which are a separate issue, and assuming that the mismatch is not so extreme that the source cannot comfortably supply the necessary current).

But if for example the source component has a coupling capacitor at its output, resulting in a substantial rise in output impedance at deep bass frequencies, or if the output impedance varies significantly in other parts of the spectrum for whatever reason, using that same passive preamp may result (depending on the specific numbers that are involved) in objectionable irregularities in frequency response and/or phase response.

Perhaps that factor, differences in how source component output impedances vary as a function of frequency, is one contributor to the divergence of opinion about passives.

Regards,
-- Al