Passive preamp

A passive preamp is one which has no amplification and provides an input selector and a volume control. In theory, the passive preamp has no distortion since there are no active devices (transistors, tubes, etc.) providing amplification. The output impedance can be quite high compared to an active preamp and, as such, is very sensitive to capacitive loading. Low-capacitance interconnects are mandatory to avoid HF rolloff and loss of dynamics. 

I have been dablling with passive devices for years, but only until a few years ago, with the encouragement of georgehifi, above, I have taken it seriously, and purchased a nice passive device, which has, extraordinarily, convinced me, that active preamps, take " somethings " away from my recordings. Some people feel that going passive, robs the music of dynamics, punch, color, or makes the music lifeless. I have found, exactly the opposite. I can say, that details and information, on every recording I play, excels, in all of these sq parameters, and every parameter. The noise background is extremely quiet...... actually, non existent. With my dac, connected, on ( always on ), and no signal, my volume can be at max, and not a sound through the speakers, which are very efficient ( yes, power amplifiers are on ). Never had this with an active preamp, tube, or solid state. System matching becomes a major factor, in appreciating one less gain stage. Most sources today, should have a proper amount of voltage, impedance, and drive ( a robust power supply ), to pass the signal to the power amplifier.......In my system, for my ears and listening, I prefer passive. No right or wrong, imo......and the debates, as to which is better, are ridiculous, just like, analog vs digital, tubes vs ss, etc. Whatever " your " ears like, this is what matters........Enjoy ! MrD.

A few of the replies are saying no added gain, or no gain stage, but more precisely a passive preamp should use no active components in the audio signal path (e.g. it would be fine to use active components for a display or to support a remote control). Active components aren't only used to add gain, but can also be used as an input or output buffer, or implement feedback, etc. Roughly anything that includes a tube or a transistor is an active component.

The downside to a passive preamp are the downsides resulting from the lack of those active components. Impedance mismatches, voltage/current limitations, etc. can all suddenly start to play a role and affect the sound quality, accuracy, or precision.

You can see how this can make selling or buying a preamp much more of a hit-or-miss situation, where one person's experience does not at all translate into another person's experience.

The advantage of a passive preamp is that you minimize any potential non-linearity and noise introduced by those components that you've instead chosen to leave out.

You use and connect a passive preamp the same way you would an active one. However there may be some situations where it is inadvisable to connect more than one input or output at the same time, depending on the internal design.

nikoaudio,

Any active device in the signal path means that the preamp is no longer passive.

MrD, and Neko both said it well.  A major problem, which I learned the hard way is: Impedance Mismatches between passive pres and amp

I loved everything about the looks and function of a Hattor passive, alas, it was a mismatch for the amp I had at the time. I wish I could have kept it, but the cost to add a buffer was prohibitive, AND the sound of Buffers is a whole nother level of discussion.

Nord offers several Buffer options for their designs