Passive preamp

bluetosman
What is passive preamp and how to connect them

A passive preamp controls the volume of the source just like an active preamp, except there’s no added gain, which means no added noise or coloration’s or distortions, they use all the gain that the source has to offer instead of throwing most of it away away.
They replace an active preamp and go in the same position, between the source and the power amp.

Quote from Nelson Pass

We’ve got lots of gain in our electronics. More gain than some of us need or want. At least 10 db more.

Think of it this way: If you are running your volume control down around 9 o’clock, you are actually throwing away signal level so that a subsequent gain stage can make it back up.

Routinely DIYers opt to make themselves a “passive preamp” - just an input selector and a volume control.

What could be better? Hardly any noise or distortion added by these simple passive parts. No feedback, no worrying about what type of capacitors – just musical perfection.

And yet there are guys out there who don’t care for the result. “It sucks the life out of the music”, is a commonly heard refrain (really - I’m being serious here!). Maybe they are reacting psychologically to the need to turn the volume control up compared to an active preamp.

Cheers George

Its just a none powered, zero gain stage, usually for source selection and volume control. basically its a volume pot, switch and in-output connections in a box. Hook it up like a regular preamp source in - amp out. 

Passives adds little to the signal ( minimaly a volume  so that's the attraction. there is advantages and disadvantages with either passive or active preamps.

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.