Active or passive preamps?

If passive preamps add nothing , then it should be the purist to the origianl signal, so why audiophiles want active preamps? And then is it true that all the passive preamp are created equal? Thx.
I am currently using a Virtual Mode Straightline 3 pasive preamp. I have used it now for over three years. A Motif MC-7 and Conrad Johnson PV5 were previously used. The passive preamp is simply much better. I agree with the approach of passive preamps. What is "put in" is what is "put out". Obviously, many active preamps must be outstanding. Some have commented that passive preamps leave out micro detail. My experience has not found that to be true. Maybe you should audition a passive in your system.
I found that while a passive preamp did indeed provide the last n'th degree of detail, it did sometimes sound a little anemic with some source components. It sounded great with my tube phono stage, good with my cd player, and anemic with my tuner and tape deck.

If you just have one or two higher end source components that can drive a passive, go passive, otherwise an active is a more general solution. I noticed my new (used!) $4000 pass labs active-only preamp actually outperformed my old $1250 adcom while running in passive mode. Barely though! And that was while running with pass amps too! I don't think all passives are created equal - some have higher quality parts which affects the signal.

Check out the adcom gfp-750 - it has both active and passive modes. I think it's the best buy out there in used audio. Being able to just flip a front panel switch to go active/passive was a great feature. Plus you can resell it pretty easily.
John_1 is certainly right that not all passives are equal. Not only parts quality but the choice of attenuator matters. Most agree that stepped attenuators based on rotary switches are superior to potentiometers--though makers and users of very expensive pots will disagree. But assuming stepped is best, it can be series, shunt or ladder configuration. I see no excuse except money-saving for series, though some very prestigious active preamps--the CAT's, for example--use them. The switch matters too. Elma is good, but Shallco is impossible to beat in my experience. A DIY passive can compete with the best commercial ones available, and if you don't use more than two sources, it can be quite simple. But as others have said, your sources have to be up to driving a passive. However, if they aren't, why not aim for ones that are? The money you save not buying an active preamp should make this a practical option.
What's a source for diy passive preamps??
If you like analytical, detailed sound then use a passive pre-amp - or - like Wadia suggests, no pre at all! However, if you want "musiclaity" in your system, with a better level of dynamics, you need an active pre-amp that buffers the input and amplifies and attenuates the signal properly.
One source for DIY passive preamps is Arne Roatcap has designed Elma switches with circuit boards, in various configurations, and has at least one schematic for a passive. He's a helpful source of advice too. If you want info from me on what I've built, email I used Elma switches once, Shallco several times, from either The Parts Connection or directly from Shallco.
Kitty- Checkout Michael Percy Audio at (415) 669-7181 for passive components and kits, and active kits for the DIY. I've used both types in my audio past, but always end up back with active (tube) pre-amps. However, the cost of a great tube pre-amp can be rather high even if you build it yourself. Keep in mind, the passive approach is limited by the length of cables, the output impedance of the sources and the input impedance of the amp(s). Goodluck.
Thx for all the inputs. My system include Sony SCD 777es and Simaudio Moon W-5 , the spkers is Maggie 1.6QR. I am looking for the preamp right now, can I go with a passive preamp? Or I have to go for a active preamp? Any suggestions? And thx.
Try Placette ($1,200) ther designer claim its superb with SACD. 30 days money back warranty. If you will do it - please report results