Do all Passive preamps exhibit this trait

Lack of dynamics hasn't been my experience with any of the passives I've owned:

Promitheus TVC
Sonic Euphoria (autoformers)
Bent TVC (S&B trannies)

In all of these cases, dynamics seemed explosive, not lethargic. The presentation also seemed airier and more detailed than actives in the same price range. I've heard the new Bent passive with Dave Slagle's autoformers and would say the same thing.

I don't doubt the calculations show:

passive controls traditionally limit dynamic contrasts and bass impact as you turn the volume down, due to the interaction between the cable, the input of the amp, and the control itself

but in practice, these shortcomings were minimal or inaudible in my system. This was especially true of the Sonic Euphoria and Bent with autoformers. Low level listening with these passives was a pleasure. They had a fullness at low volumes that seemed more natural and proportional than an active.

However, a back-to-back comparison of the Bent TVC and an Audible Mod3a indicated something was missing in the midbass area. A friend and I both agreed that the Mod3a was noticeably warmer in a good way. After a year of intense interest in passives, I've returned to an active, but I still believe a good autoformer-based passive will outperform most actives in the sub 1000 category.

Ralph, glad we're on the same page with TVCs, although I trust your passive volume control option for the M-60s is well designed.

Mingles, my K&K TVC (S&Bs) outperformed my Cary SLP-98 ($3995) and Joule Electra LA-100 MkIII ($3750). I'd venture to say the Bent units in particular, either the S&B or Slagle models will outperform many preamps, both sub and over $1000.

Now Dave Slagle has come out with a manual DIY version using boards developed by John Chapman for a ridiculously low price. Just add a case and some RCAs and you're done. Even if you had someone build it for you it would still be a bargain.

See here:

http://www.audiogon.com/cgi-bin/cls.pl?preatran&1230319450&/Intact-Audio-Slagleformer-Modu

Mingles, sure sounds like your experience is similar to mine, but keep in mind also the caveat 'properly designed' which I am careful to use. IMO, most of the active line stage technology you see today seriously trails behind amplifier and phono preamp technologies. I feel that this is because many line stage designers are not even aware that control of the interconnect cable is one of the goals/functions of the line section.

Thanks Elizabeth for responding. I too feel that the GFP-750 is a fine preamp in passive mode and for the money is a bargain. My only serious complaint with the GFP-750 is better described in this excerpt from an online magazine review:
At various listening sessions, my son Marc, a trained musician for both trombone and guitar, (not an audiophile) would join me and add his input. One CD we listened to was Keith Jarrett’s At The Blue Note: Saturday, June 4, 1994, First Set (ECM1577 78118-21577-2). The trio was beautifully recorded and it became evident that what was missing was the air and extension in the high frequency range, which manifested itself on Jack DeJonette’s delicate and varied cymbal work. To paraphrase Marc, it was as if the decay of the cymbals was cut short. In the bypass mode, this was slight but noticeable and to a lesser degree with Keith Jarrett’s piano. The bass resolution, timbre, and resonance of Gary Peacock’s bass playing were right there with no apparent differences in achieving the full body of the instrument.

Through the Adcom, the dynamics of the piano and the full body of the instrument almost matched the direct feed, but that slight loss of full note decay or ambience was just barely noticeable. And I do mean barely. I feel this is still quite an achievement and more an act of omission than addition of coloration or artificiality. Consider also the fact that an additional set of interconnects and connectors are in the chain. This in itself will cause some losses to the sonic protrait.