Passive Preamps

It is good to note that passives come in different flavors. I am not a technical expert in this, but a transformer volume control - TVC - I understand will generally work better and in more instances then just a resistive attenuated volume control in both impedance matching and for a fuller sound.

As I've said, with my TVC I don't lack any dynamics -- everything is as 'colorful' as it was with the few active pre's I've had, with the added benefit of more transparency and air between sounds. Bass is low and tight, highs are extended and detailed. Soundstage is better defined.

Another option is an active/passive pre in the same unit. Wyred 4 Sound, Placette and others make such pieces.

I second Tholt on the Promitheus TVCs. One more point I would like to add is that in case of TVC the amp's input sensitivity is VERY important. With a TVC, the input sensitivity of a power amp better be below 1.5V. With this n mind, there is absolutely no loss of dynamics or body or weight. The positives aspects with the addition of a TVC in your system are something to be heard and seen rather than describe in a thread.
So, system matching is very important.

10-04-09: Milpai
One more point I would like to add is that in case of TVC the amp's input sensitivity is VERY important.

Good point.

Also, the output impedance of the source component should also be low to ensure extended and defined bass. I find below 200 ohms is optimal in my system

Many tube output sources do not qualify. Something to keep in mind when considering a passive preamp.

One more point I would like to add is that in case of TVC the amp's input sensitivity is VERY important. With a TVC, the input sensitivity of a power amp better be below 1.5V.

Why is this? Is it because of the TVC volt-to-current conversion from the source? ie an amp with lower input sensitivity means it's easier to drive to full output power? apologize for the laymans terms. What would a 1.5v or higher amp input sensitivity equate to sonically?

Tholt,
no need to apologize. I was not aware of the significance of these measurements till I asked these same questions to a GURU on this forum. He has explained in detail about the TVC and the attenuation it does to the incoming volts. Send me a PM and I can send you the explanation he gave me.