Cd player what is..

In my own experience most balanced input devices will also accept unbalanced input signals but you will probably notice a little extra noise due to the unbalanced connection not being shielded. When i switch from unbalanced to balanced connections I notice a reduced amount of hum as well as Clearer top end.
I hope that I am helping you out any as most of this is just from my own experience working with professional equipment. Hopefully someone else may be able to elaborate on this.

Dan
 
Unbalanced cables are in fact sheilded. The problem is that the sheild is usually tied to the negative - waveform of the signal. So the noise is tied to the signal with no way to cancel it.
Keep your cables from an unbalanced CD player short
(ie:less than 10 feet) and the "sound" should be fine

Otherwise you may pick up audible noise and hum. You may even pick up noise with shorter cables than this.

The noise problem is one of the reasons why FULLY balanced operation is desireable.

The whole point of balanced lines is for most of this noise to be bled off the sheild to ground(which no longer touches either the + or - of the audio signal) and whats left gets cancelled at the balanced input.

But everything involved must operate in balanced mode.
The output device(CD or whatever) must have balanced outs.
The cables and connectors must be wired for balanced operation.
The input device(your Preamp) must have balanced inputs.
Anything less is not true FULLY balanced operation.

If you want to purchase a CD player with balanced outs consider the brands mentioned above and also HHB.
The HHB Burn-it 830 Plus is a CD recorder that has balanced outs.
But I agree with djquicksiver in that the choice between brands should really be the listeners.