Do all Passive preamps exhibit this trait

The idea of passive is to not color the sound? Get something like a creek OBH-12 which is as passive you get and see what your amp and speakers really sound like.

Typically passive preamps do not exhibit this trait, but depending on the rest of your system you may have trouble finding what you are looking for. A good passive preamp should not add or subtract anything from the equation. However, impedance mismatches and cable issues could cause the problems you are describing.

In my experience I have preferred transformer or autoformer based passive preamps versus their resistive counterparts. The TVC/AVC passives tend to match up better in most systems. Impedance matching is important with passives. Just changing the setting on the volume control could impact the output impedance on the passive. Also, since we don't know the rest of your system there are a few things you should look for moving forward.

1. Your source has enough output to drive the passive (2V or better with low output impedance).

2. Your amp should have high input impedance (50k or better) and be sensitive (1V or less to drive it to full power).

3. Try to keep cable lengths short between the source and passive and passive and amp. This is more applicable to the resistive passives, but probably a good practice with any type.

If it were me, after determining if my system was passive friendly I'd try a TVC/AVC and see what happens. Lots out there to try that you can find used for good prices. Promitheus, Antique Sound Labs, and Sonic Euphoria come to mind.

Also try reading this:

http://www.stevens-billington.co.uk/page102.htm

One other thought, try the new Pass B1 unity gain buffer preamp. The buffer eliminates the impedance issues and the circuit does not have a gain stage. Sounded really good at RMAF when I heard it there.

If you don't want to pay the Pass dollars Audiogon member Rawsonte has been advertising a couple DIY versions here for great prices.

Maybe that "more extension and detail" you experience with this pre-amp is exactly what makes it fatiguing and is not representative of what an high quality active pre-amp does when it does highs right. For me, highs done right, is like a star against a night sky. The sky is darker, the star stands out more sharply BUT is not, in itself, brighter. Does that make any sense to you?

In my experience with other units v passives the biggest difference can be in dynamics. As mentioned set up of a passive to compensate for IC impedence problems, etc, can make a big difference.

IMHO, you just need a better (not necessarily more expense) active pre-amp. Oh, BTW, if you decide to go with a passive be sure to do lots of research 1st. They are NOT all neutral, some are additive or subtractive.

I have been using a Reference Line Preeminance 1A passive preamp for the last two years. I find that recessed treble and listener fatigue comes primarily from poor recordings.

The passive to my ears lets everything through as recorded. It has meant that some CD's sit on the shelf because the recording values suck.