Preamps for dummies that would be me

Theoretically, a wire should pass only signal, and a pre should pass only signal, and the original mike should pass only the original signal (of voice), and the mixing board should pass only signal, blah, blah. But the fact is, the empiric fact backed by experience - as in a concensus of the relevant peer group, which is what determines what evidence will be considered valid in a scientific discussion - is that active preamps make a large difference in sound quality in terms of musical involvement, and increasingly so as one's system increases in the ability to so catalyze that listening experience.

Do I know why? No.

Do I think its healthy to ask why? Certainly.

But the fact is that the consensus among the best system builders is that an active pre is essential.

Will it always be that way? Maybe not, but it is now.

That's why someone can talk about how passives should sound better theoretically but in practice they have a CAT.

Every piece of matter between the voice and your ears "launders" the sound. Right now, the active pre translates the musical meaning to a greater degree than the passive in the best systems.

Stereophile via Steve Stone tried to push passives several years ago when CD got going, but it failed and no reviewer I know of with a great system goes passive now. There's a reason for that and it has nothing to do with the rigors of scientific theoretics or the functional requirements of being a reviewer and swapping equipment.

If you don't have the scratch for a good tubed pre and run only a digital source, then many times a passive is the way to go. But that doesn't mean its THE way to go...

Without wishing to get too technical (because I'd probably demonstrate my ignorance) I believe that the biggest problem with a passive preamp is that of impedance matching. Passive preamps can offer a lower input impedance than some sources are able to drive. If this occurs then the sound is robbed of dynamics.

This problem is system dependant, because it depends on the output impedance of the source and the input impedance of the power amp. In a system with a very low output impedance on the source and a very high input impedance on the power amps a passive preamp might work well. There's no denying that a passive pre is transparent and cost effective in this situation.

If your source has a relatively high output impedance and your power amp has a lower input impedance then using a passive pre might not work since the output stage of the source will not be able to drive enough current into the low input impedance of the preamp. An active preamp will be able to offer a better match of the impedances in this situation, and if it's a decent preamp then it will also be pretty transparent, and will not be coloring or conditioning the sound at all. It's a hell of a lot cheaper to build a quality amp at preamp current and voltage levels than at power amp levels, so there's really no reason an active pre should be any less transparent than your power amp.

So in summary there is no blanket rule that active is better than passive or vice-versa. I believe that impedance mismatches are the core issue in system matching, and the reason that you can't apply simple rules and then buy components without first demoing them.

OK, let's try again...

About what Gs5556 said:
CDP's and DAC's have steep HF filters kicking in at around 20KHz to reconstruct the analog signal and keep HF digital artifacts at bay. In contrast, any competent active preamp will have its upper -3dB point (and often even the -1dB point) well out above the audioband. Given that truth, what do you propose to be the magic mechanism in active preamps that is supposed to "launder" your allegedly dirty signal coming from the CD source and make it "clean" for the power amp? As I and many others know from experience, the direct, unattenuated and unpreamped output of a CD source cannot not harm your amp, speakers, or ears on any basis other than possibly that of sheer volume.

You then posit a contradiction, by suggesting (correctly, if not comprehensively) that a passive attenuator can interact with the source's output impedance, the amp's input impedance, and the cables' capacitance, to cause mis-matching and insertion losses which can combine to roll off response prematurely at the LF and/or HF ends of the audioband, sapping signal fidelity and drive vs. an active preamp - but then put forth in the same breath your contention that a passive attenuator will pristinely pass along all of your alleged digital HF garbage to the amp unhindered vs. an active preamp, which you suggest will somehow filter this alleged spuriae that you claim is part of the CD output signal.

Well, which is it? - it can't be both. In any given situation, a passive attenuator will either preserve the fidelity of the input signal or reduce it vs. an active preamp, and the same thing applies the other way 'round; you can't simultaneously but selectively argue that passive attenuators will *both* preserve and destroy fidelity (as well as making the same argument in reverse for active pre's), depending on what's conducive to bolstering your position in the debate. As for your claim that you "personally cannot stand to listen" to a CD source not run through an active preamp, I have to assume this rhetoric is based as much on what you (erroneously) think about the output of CDP's and the action of active pre's, as it is on what you actually hear. (Which isn't to say that in any particular instance, one might not prefer the sound of their CD source run through an active preamp [especially as compared to its sound run through some other sort of attenuator, or volume-controlled in the digital domain], but that it won't be for the 'reason' Gs5556 alleges.)

If a passive preamp did the job better than my Ayre for the same price or less (and had phono as magical as the Ayre), I'd buy it in a heartbeat. My main goal iis end product sound quality and not fancy smancy equipment (unfortunately, I have found that if you really want to get world class sound.... well, you need to dish out at least national class dolars...) Eeeking that last %10 of heavenly sonic quality from your speakers tends to be pricey at best.

I am the first to tell folks that if I could get the same sound out of coat hangers used as speaker cables as I could my Nordost SMP speaker cables, I'd be the first to raid all the closets in the house. (I remember an audio designer telling me that monoblocks and coat hanger could sound very good. I asked him to demonstrate, but he declined.) LOL.

KF