wht does a preamp do?

When I first got my Audio Aero Capitole CD player I ran it through the pre on my receiver. I had a hard time getting past my own personal bass and treble adjustments that were on the receiver.

Then I tried feeding the Audio Aero to the amp (McIntosh 2102) and bypass the receiver. This sounded much better. Using the Audio Aero's tubed volumn control I was able to power two amps into two locations with that balanced and unbalanced outputs.

At the moment I am using two unlike amps in the same room to bi-amp and I am now running the signal through a McIntosh CR12 AV system which has 4 individual preamps that can feed from one source if I like and this allows me to somewhat correct for the mismatched amps. With the McIntosh it sounds really good.

I have been playing around with passive attenuators for the last couple of weeks, it has been hellish trying to get it to function properly, I have tried several configurations and values, from the single pot, to a resistor loaded pot, to a series resistor and a pot, Then chnanging the values of the resistor and the pot.
All this because I made a simple test pot box and it sounded amazing. My amps have very low sensitivity, that is supposed to help. The passive is intalled inside the amps (monos) and 3 inches away from the input tube. One IC only.
I have noticed that changing the values changes the sound of the passive completely. If I go to the lowest resistor value for the pot I get more dynamics, If the series resistor is too high it cannot solve complicated passages of the music, if it is too low the extension of the high freq. will go down (no highs), so it has been a fine tuning effort but clearly rewarded.
The main diferences I noticed between the passive and the active are:
Passive:
-Darker backround...incredible backround! no noise.
-More extension on both sides (when porperly intalled)
-The music is more relaxed but dinamic non the less.
-The tone of the instruments seem more natural.
Active:
-Dynamics man, the impact of the drums and cimbals and horns is so big it puts you there.
-The tone of the instruments seem very real. (dinamics help here)
-I would not have noticed but yes there is a certain distortion not heard on the passive.

To round it up I would say the active preamp is more "Be There" distortions and all, while the passive is hypnotical...

Beware; I used to have a top of the line DAC with volume control and in no way would it compare to the passive I have now, I cannot compare side by side since I sold it about a year ago, but it seems pretty obviuos to me now.

I cannot tell you I prefer one over the other...

I can run my B+K preamp in passive mode, and I've spent the last couple days messing around with passive vs. active mode. One might think that because it's a decent, but not terrific preamp that passive would sound better. But I've found exactly what jsadurni found--better imaging, brighter and the like with active mode. The voices seem to hang there in the air with the active mode, instruments come from outside the speakers. It does reveal imperfections--some disks are too bright on active mode. I really expected to prefer the preamp in passive mode, but I don't.

Cheers,

Matt