Tube CD player and no pre-amp

...even if the Pass impedance is low the tube output impedance can be neglected in comparison to Pass input.
Is there an analogue volume control in your CD-player?
Most-likely if you will be using a passive preamp you will have a very small volume range to operate and the length of interconnects will matter.

It is my opinion that the length of the inconnects will make a difference, especially since you are removing the pre-amp from your system (you may lose some drive). The type or brand of interconnects make a difference too. I've heard varying results in systems with long runs using different interconnects. So far, the Nordost Quattro Fil or Valhalla cables performed well in systems with long runs, although these ICs are extremely costly.

I've had very good results in my system using an amplifier with a volume control, replacing my pre-amp. That is another alternative.

Hey,

Currently, I am using Cal Audios transport and dac. In between, they are connected to a Meridian digital preamp that attenuates the volume in digital domain. The dac then connects directly to the amp. This lacked a little bit of drive, as Hawaiikid advised, but sounds super clean and detailed. However, upgrading the powercords to the transport restored the "drive". In my case, I am using a Virtual Dynamic powercord. My system no longer begs for a preamp.