Can a direct CD to amp connection degrade sound?

I've had a Cary 300/200 for over a year and always ran it thru my Rogue 99 pre amp. A week ago I tried going CD to my Rogue Zeus amp direct. Many ads suggested that with a volume-control CDP, a pre was a waste. Sounded right on paper, sounded very wrong in person. The sound without the pre was flat,tinny. There was no air around instruments. What happened? How can a pre improve a CDP's signal when the whole point is to leave the signal unchanged? Has anyone tried it both ways and compared the results?
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In line with Elizabeth's post, does the Cary offer the ability to vary the maximum voltage output? When my vinyl source was offline, I esperimented with running my Wadia 302 directly into my amp with excellent results, but I had to vary the output voltage so that in the Wadia's sweet sport (volume control between 67 and 99) it was not over or underdriving the amp. Of course if it is purely an impledance issue this may not help.
I have had the very same experience as you - three times. I think direct connection only works well in certain special cases.

Yep. Sometimes you can get luck and have a good impedance match. But generally, a good line stage is needed to achieve good sound.
of coarse a good preamp is better. only use direct if you have no preamp otherwise why would they make preamps??????? also volume controll on a cd player is best at full volume
My Wadia 830 and 861 experiences replicate yours when using a Supratek Chenin. The Chenin was an improvement over going direct.
Throughout the years, I've seen more negative than positive comments when people go directly from the CD player to the amp.
I am running an Art Audio PX-25 direct to a Audio Aero Capitole MK2 and it sounds better in my system then it did with a BAT VK50SE!!!!! You have to listen to it in your system and let your ears be the judge--------
I have tried a couple pre-amps with my GNSC modded Wadia 850, and never found anything that gave a significant improvement. Most take something away. Even when I felt like there was an improvement in some parameter, there was more lost in other parameters that made it a net loss. IMO
Neither unit mentions impedance so I assume all you can do is try. The Cary can be set for a lower output voltage and I may try that. Anyway, thanks for the education
Manorraul, contact the manufacturers. They should be able to give you the spec's.
Never worked for me. When I tried it, the system was all but unlistenable.