Hello iansr,
That's an understandably intuitive question to ask. For years now most all modern recording studios have been recording their artist sessions directly to 24 bit (Sometimes much higher) resolution and storing and mastering in the digital domain. The quality and precision (Same thing) of these encoding A/D convertors is quite exceptional. So asking whether digitizing an analog signal is deleterious to the final sound of the reconverted analog signal is a little mute.
The real question involves a few more levels; A) Is the quality of that initial analog source of high quality or not (Garbage in, garbage out), and, B) If it's a phono signal, is the RIAA stage inside the D-Premier a good one, and, C) Is the A/D convertor inside the D-Premier of high enough precision to not add an imprinting distortion to the converted analog signal?
Here's what is found on the FAQ section on Devialet's website that addresses your question from their viewpoint - "Internally routing all the analog inputs as differential signals although received via a "single-ended" RCA connector, with an insulating washer (a very meaningful detail), which makes all the difference: doubles the needed devices of the analog chain hence its cost and removes all the ground noise and distorsion, making the phono ground connection virtually useless, providing a configurable resistive (9 to 460 Ohms) and a capacitive (100 to 700 pF) loading of phono MC cartridge for optimal operation, paying the same attention to noise and distorsions as on the DAC and the ADH amplifier, providing the same extremely wide and ultra flat (FIG.) frequency response</a> as the digital inputs, totally independant from the speaker impedance, except a security sub-bass cutoff at 0.1 Hz for speaker safety purpose (no cutoff in digital), using the most optimal and accurate RIAA corrector, volume control and gain stage architectures, clearly demonstrates the analog inputs have not been designed for legacy purpose or "connectivity", but with the Devialet quality and total lack of compromise. Should we disclose that it's the most expensive section of the whole product? Should we mention some customers are using their D-Premier as an ultimate "RIAA-ADC" to rip their vinyl LP collection and build a bridge between recording technologies? But of course when it comes to playing genuine digital music, however meticulously designed, the analog inputs cannot rival with our internal DAC for architecture reason (shortest path): because all the blocks are so transparent, what you will end up hearing is... the external DAC. "
I hope that helps - John