Oppo 105 and Hegel H160 DACs

This is nonsense. Do you have any noise or jitter measuremtns to back up this claim? You can use the Oppo as an excellent pre amplifier. The DAC inside is first rate.

The answer is it depends.  If your connecting your Oppo with the XLR or RCA outputs into one of the line inputs of the Hegel integrated then your bypassing the builtin DAC on the Hegel.  If your connecting to the Hegel via USB or some other digital input, then your using the Hegel’s builtin DAC. How are you connecting the Oppo to the Hegel? 

@nycjlee -- I'm using the xlr outputs on the Oppo

Those are analogue, so you are using the Oppo's DAC. If you want to use the Hegel's DAC you have to use the Oppo's digital output into your Hegel's digital input. I would expect the sound to be very similar or identical. However, the hard bit is to do a proper comparison. Apart from the fact that it should really be double blind, you have to make sure that levels are exactly matched (within 0.2 dB). Also, the gain between the analogue output of the Oppo and the analogue input of the Hegel should be properly matched to avoid clipping. If you use the digital connection you may hope that you avoid this issue, provided the internal gain structure of the Hegel is correct.

To claim that the Oppo can be excellent pre amplifier is nonsense, It is very good blu ray that can be a decent CD transport but certainly not great one .Pure CD transport with quality coax cable will upgrade the the dound by far.