Hi Piotr,
To answer this, I should note that Oversampling (and subsequently the Upsampling option on your Bartók) is directly tied to the filtering process - I appreciate that sometimes isn’t clear.
The short answer is that if you don’t Oversample (and perform the subsequent digital filtering to remove Nyquist images), you either:
- Have loads of Nyquist images in the audio signal which are not filtered up to wherever your analogue filter is (100kHz in a dCS DAC) which would ruin the sound quality.
- Or you run a very steep analogue filter at 20kHz-22.05kHz to remove these images, which would have real problems of balancing left and right channels and would be non-phase linear.
This filter is then the same for all sample rates, so using such an analogue filter defeats the point of higher sample rate audio.
Using digital filters from 20kHz-100kHzby performing Oversampling to remove Nyquist images there, then having a gentle analogue filter removing anything above say 100kHz, is a very good way to address the problem of Nyquist images. Not Oversampling means you are subject to loads of images, or a brutal low analogue filter, both of which will harm sound quality.
For more info on filtering, take a read of the posts here. The whole series of posts explains why we do things the way we do in our DACs.