Kubrak wrote:Upsampling is just another form of digital filtering to avoid antialiasing on systems that have poor DA.
If audio signal is sampled 44.1 kHz, no upsampling, resampling, digital filtering is not able to add any information to signal. It may only better or worse mimic ideal filter which has to cut off frequencies above 22.05 kHz to avoid aliasing.
Not to forget–
The great majority of DAC-chips do exactly this for DA-conversion:
Internal upsampling to a way higher sample rate, plus calculation of a digital filter, then output the result on that very high sample rate.
This is the reason why there is a choice of reconstruction filters e.g. inside ADI-2.
Preliminary upsampling just dublcates some of that process.
Kubrak wrote:And there is no ideal solution for that case by definition. There are always compromises by definition, one cannot beat mathematical reality. One may prefer one method, the other another, but none of them is perfect, none of them is "right".
That‘s exactly the point:
DA-conversion and it‘s filtering is a compromise between:
• Frequency response linearity of the upmost range.
• impulse response precision and shape.
• Aliasing artifacts inside the audible range.
The optimization is in the range between so called “Sharp” filters on one side, that optimize freq. response and anti-aliasing, on cost of impulse respone –
and on the other side the NOS filters that optimize impuls response on cost of audible high frequency loss and aliasing artifacts.
IMO the best compromise is located in between:
Slow Filter (on AKM DACs) and SD-LD and Brickwall (on ESS chip based DACs).
They offer good and natural shaped impulses (no pre-ringing, which doesn’t exist in nature), while sacrificing a little bit of upmost treble and allow a minor amout of aliasing.
The result is cleaner and more detailed, with better separation of high frequency instruments like hihats and shakers or other percussion instruments.
The ambience, room sound definition benefits either from that.