[Charles Calkins]

 
    Hi Guys:
   
                What is the difference between a preamp and a passive preamp?

                 I never heard or read anything about a passive preamp until the other day.
                  I always thought a preamp was a preamp.

                                               Cheers
                                             Charlie

[Samac]

An (active) preamp adds gain to the signal and a passive does not. At least that's the way I've always understood it.

Cheers,

Scott

[RDavidson]

An (active) preamp adds gain to the signal and a passive does not. At least that's the way I've always understood it.

Cheers,

Scott

That's mostly right. There are also active preamps that don't add voltage gain. They're sort of a hybrid between passive and active, sometimes referred to as buffered passives. This is my preferred preamp. You get nearly all the benefits of a passive preamp without the electrical mismatches that can occur with said devices. There are tradeoffs with each type of preamp and system compatibility is always a factor.

[Folsom]

When I read "preamp" in no way do I read "adds gain" unless it's tube based. There's no reason to think it will unless stated.

A preamp is just something that goes before an amplifier, and explicitly always has volume on it. An active device without a volume control that adds no gain is a buffer. An active device that adds no gain and is a buffer but also have volume control is a preamp. A device that adds gain only is a gain stage/ line stage. A device that adds gain and has a volume control is a preamp. Preamps may also have phono section and source selectors.

A passive unit changes the impedance network so that the source struggles a bit more to drive the amplifier as well as possible, and provides at least volume if not also source selection. An active unit typically recreates a better impedance scenario where instead of a high output impedance from a passive preamp (volume) it now has a low output impedance from the active circuitry. Some tube preamps have marginally low output impedance.

Tubes almost always have gain, btw, if that isn't clear.

[RDavidson]

I knew someone here (with technical chops) would get into the semantics of the term "preamp."

[f2a]

yes for 2 mono block  without volume pot ...preamp can let user to use volume .
but  good active  preamp can  help to quality of sound. not only in voltage gain ...it is   difficult to  find good active preamp so someone use passive .
 

[LJ3]

An active preamplifier can improve but also degrade sound quality. Generally, an active preamplifier affects the sound of the final amplifier.
In order not to affect the power amplifier's path, passive preamplifiers are often used. The preamplifier can be omitted if the power amplifier has a volume control or, for example, a source such as a CD.
 

[rollo]

  They each have their place. Passives require a source with at least 3V output. An Amp [ SET ] with a low input sensitivity of less than 1. Without those criteria it will sound lean or bright.
  Active can help drive a low voltage CD player or DAC. Adds weight to sound. Adds needed gain for phono stage as well.

charles