Do all Passive preamps exhibit this trait

I am using the Adcom gfp-750 with two Classe Dr-15 amps (in bridged mode), Apogee Stage speakers, Marantz SA-1 SACD Player, Krell 300cd player, Herron MM phono stage with VPI Scoutmaster turntable. Cables have been Cardas Golden Reference (very low capacitance) and Nordost Quattro Fil. I've switched between both cables and haven't noticed much difference as it relates to treble extension. There was an online magazine review done which noticed the lack of transient decay when the Adcom was used passively. I suspect that's it's a feature of this preamp which can't be overcome regardless of which cables and components are used. Can anybody confirm this or had a similar complaint with the GFP-750?

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.

I may have disovered the trouble. For the past two weeks I have been using my Krell 300cd player with single ended interconnects. Previously (for 6 years) I had been using it balanced. With a full-level 1kHz sinewave, the output from the 300cd is 4V from the balanced outputs, 2V from the unbalanced. I'm would say the output is too low unbalanced to make a satisfactory match with this passive preamp.