Not sure how the Cambridge 851D sounds but I have a 851C and it's a great player. I'm curious how much time you have on it and what is the rest of your system? My local hi if shop which carries both Parasound and Cambridge gear has both the P5 and 851C on the same system with a Parasound A23 driving either Magnepan 1.7 or 3.7i. I've done the comparison with the staff there and no one felt the DAC in the P5 is even close to the 851C. Not knowing your system it's likely the 851D is more revealing than the P5 DAC and maybe you're hearing something else in your system you're not liking such as your digital cable. Give the 851D more time to burn in. I will add my 851C shines with a better power cord. I have a kimber PK10 Gold on mine with Clear Days ICs.
The P5 is a nice pre for the money and full of nice features as well. Not sure how the DAC in the P5 compares with lower priced CD players but I suspect it does well. My guess is an older player with digital out will benefit running through the P5 DAC, but a newer player in the $700 and up range will be better with its own DAC.
Again I will add my 851C took a long, long time to settle in and I have not heard the 851D but I would sure think it's equal to the 851C. Give it time.
The P5 is a nice pre for the money and full of nice features as well. Not sure how the DAC in the P5 compares with lower priced CD players but I suspect it does well. My guess is an older player with digital out will benefit running through the P5 DAC, but a newer player in the $700 and up range will be better with its own DAC.
Again I will add my 851C took a long, long time to settle in and I have not heard the 851D but I would sure think it's equal to the 851C. Give it time.