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Upsampling / transcoding - a question


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The theory seems to be that DACs themselves apply various forms of processing, so it's beneficial to the DAC's operation to do the "heavy lifting" of this processing with a more powerful PC beforehand.

 

Trying to understand this from a non-technical viewpoint, it makes complete sense if the replay software and DAC are designed from the outset to work together in this way (as I believe at least one combination is) or possibly if the DAC itself is user-configurable as to what processing it applies, but if we are just mixing and matching replay software and DACs isn't it possible that prior software upsampling or transcoding has no real effect on the load presented to the DAC, or actually makes things worse compared with simply passing a "native" file to the DAC?

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The in-DAC processing is quite standardized, and thus what the software players do can be as well.

 

In-DAC, the input sample rate is brought up to 352.8 or 384KHz resolution, then goes through a sigma-delta modulator to turn it into a pulse density modulated bitstream at MHz rates. (DSD matches the latter description.)

 

Depending on what the DAC will accept as input, these steps can be partly or fully accomplished in software, so the DAC doesn't have to.

One never knows, do one? - Fats Waller

The fairest thing we can experience is the mysterious. It is the fundamental emotion which stands at the cradle of true art and true science. - Einstein

Computer, Audirvana -> optical to EtherREGEN -> microRendu -> ISO Regen -> iFi NEO iDSD DAC -> Apollon Audio 1ET400A Mini (Purifi based) -> Vandersteen 3A Signature.

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This is a hit-and-miss situation IMHO.

With upsampling software you are stacking filters – unless you upsample high enough to bypass one or several of the dacs internal processes. This is why upsampling to DSD has become popular. Upsampling settings in A+ and HQP are dependent on the dac.

 

My Ayre dac sounds notably worse with upsampling on turned on (in A+, Redbook to 24/176).

Roon client on iPad/MacBookPro

Roon Server & HQPlayer on Mac Mini 2.0 GHz i7 with JS-2

LPS-1 & ultraRendu → Lampizator Atlantic → Bent Audio TAP-X → Atma-sphere M60 → Zero autoformers → Harbeth Compact 7 ES-3

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This is a hit-and-miss situation IMHO.

With upsampling software you are stacking filters – unless you upsample high enough to bypass one or several of the dacs internal processes. This is why upsampling to DSD has become popular. Upsampling settings in A+ and HQP are dependent on the dac.

 

Yes, absolutely. Best to have a DAC that will accept DSD and/or 352.8/384KHz input. Even if this is not the case, if you know something about what is involved you may be able to improve things.

 

My Ayre dac sounds notably worse with upsampling on turned on (in A+, Redbook to 24/176).

 

I would guess that if you changed the iZotope settings to something more along the lines of a minimum phase, shallow slope filter with a rolloff slightly below Nyquist (.99, .98, around there), you might get a better result. Or with HQP you would use one of the minimum phase apodizing filters. Don't know if you've tried this already, but you might want to see how those work.

One never knows, do one? - Fats Waller

The fairest thing we can experience is the mysterious. It is the fundamental emotion which stands at the cradle of true art and true science. - Einstein

Computer, Audirvana -> optical to EtherREGEN -> microRendu -> ISO Regen -> iFi NEO iDSD DAC -> Apollon Audio 1ET400A Mini (Purifi based) -> Vandersteen 3A Signature.

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I tried every combination... Charles Hansens filter is best left undisturbed.

Now and then I run HPQ and upsample to DSD64. The later versions sounds very good indeed. But I prefer the A+ app.

Roon client on iPad/MacBookPro

Roon Server & HQPlayer on Mac Mini 2.0 GHz i7 with JS-2

LPS-1 & ultraRendu → Lampizator Atlantic → Bent Audio TAP-X → Atma-sphere M60 → Zero autoformers → Harbeth Compact 7 ES-3

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I tried every combination... Charles Hansens filter is best left undisturbed.

Now and then I run HPQ and upsample to DSD64. The later versions sounds very good indeed. But I prefer the A+ app.

 

I have a similar experience with my QB-9 DSD. I really wanted to like HQP, and tried a lot of configurations, but I just didn't like the results with HQP upsampling PCM. The results were better upsampling to DSD64, however I still preferred PCM with native sample rates via Pure Music.

Main System: Mac mini (Audirvana+, MMK, JS-2) -> ISO Regen (LPS-1) -> Icron 2201 (Rex LPS-1.2) -> ISO Regen (LPS-1.2) -> Ayre QB-9 Twenty -> Headamp GS-X Mk2 -> Classe CT-M600 -> KEF Reference 201/2

 

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