I’m stuck between 2 schools of thought on this:
The fewer circuits and cables in the signal path, the better the sound should be. Therefore, eliminating the dedicated preamp and running the Oppo’s output directly to the power amp should increase sound quality.
A separate dedicated preamp will likely have better circuitry and signal quality than the comparatively basic gain stages in the Oppo. Therefore, using a separate preamp should deliver better sound quality.
Thoughts?
1: Correct, the output stage of the Oppo is 47ohms at over 2v completely matched to drive any poweramp, unfortunately the digital domain volume control can "bit strip" if used too low, this is usually below 75% of full but can vary, so if you can use it above 75% then your hearing the Oppo at it's best with no "bit stripping" warts and all.
2: A dedicated preamp "may" have "better" circuitry, but the best preamp is one that sounds like "straight wire with gain" but the signature will be already given to it by the Oppo, so if the preamp is that good it will let the Oppo’s signature sound through and not sound any different, if not it’s got distortions that will colour the sound, maybe to your liking, maybe not if you were happy with the Oppo’s own sound direct.
Cheers George