What is the point of upsampling?

[solderdude]

So there is a benefit in / requirement for upsampling.

I don’t understand why it is being questioned all of a sudden?

Only when you have a really crappy DAC (filterless NOS regardless how expensive) or one that only has a poor slow reconstruction filter then you can improve signal fidelity by using upsampling (that has a good filter, there are poor filters too).
For your normal standard DAC there is no benefit.

 

[solderdude]

External upsampling can potentially improve on internal chip-upsampling, particularly when you bypass all internal filtering and modulation.

Many manufacturers are now doing away with off-the-shelf SRC and even D/A conversion and the measured performance they produce is putting them at the top of the scale.

Unfortunately not many bench tests are available of internal vs. external upsampling of the same DAC

Manufacturers make them because there is a demand (so market) and people are willing to pay for it. People believe in R2R as it easier to 'understand' and wildest theories are floating around.
There are no bench tests using external upsampling because it defeats the purpose of the DAC (sounding different or supposedly having better 'impulse response')

 

[Dennis_FL]

So this Roon help is not accurate ?

 

[solderdude]

Truths mixed with myths is a great way to promote stuff. There are also manufacturers of equipment using this strategy .... believe it or not...

 

[Julf]

So there is a benefit in / requirement for upsampling.

There is a benefit in the DAC if the filters are designed to take advantage of it. There is no benefit in upsampling the material going into the DAC.

I don’t understand why it is being questioned all of a sudden?

Context is everything...

 

[Julf]

But, for example, if I need to obtain the values of the peaks in the waveform, the shape matters very much, doesn't it? There are other use cases than just listening.

Sure, there are scenarios like that. What I should have said is "from a sound quality point of view, it doesn't matter".

Stepping back a fraction, you mentioned that "DACs do upsampling internally so they can apply digital filtering". In a sense, I did not fully understand your statement, as the cause–effect relationship was somewhat unclear. Would it not be more correct to say that the DACs do upsampling (e.g., by adding zeros into the digital signal data stream), and then they perform digital filtering on that new data stream to remove the unwanted signal content that is contained in the new data sequence, essentially resulting in an upsampled interpolated digital version of the original waveform. The DACs do digital filtering as part of the total upsampling interpolation process, which is not what I took away from your description.

What I was trying to convey is that upsampling DACs trade analog filtering for digital filtering - the amount of filtering still stays roughly the same. It's just that it is very hard to make good, very steep analog filters.

 

[Julf]

External upsampling can potentially improve on internal chip-upsampling, particularly when you bypass all internal filtering and modulation.

And on how many DACs can you do that?

 

[tuga]

Only when you have a really crappy DAC (filterless NOS regardless how expensive) or one that only has a poor slow reconstruction filter then you can improve signal fidelity by using upsampling (that has a good filter, there are poor filters too).
For your normal standard DAC there is no benefit.

I will accept if you say that there is audible benefit (though you’d have to prove it) but if external upsampling lowers the noise floor and reduces jitter then there is a benefit.

 

[tuga]

Manufacturers make them because there is a demand (so market) and people are willing to pay for it. People believe in R2R as it easier to 'understand' and wildest theories are floating around.
There are no bench tests using external upsampling because it defeats the purpose of the DAC (sounding different or supposedly having better 'impulse response')

If filtering were perfect different filters and noise shapers would not measure or sound different.

 

[Julf]

If filtering were perfect different filters and noise shapers would not measure or sound different.

Do they?

 

[Julf]

if external upsampling lowers the noise floor and reduces jitter then there is a benefit.

But does it?

 

[tuga]

Do they?

Yes

 

[tuga]

But does it?

Yes

 

[solderdude]

I will accept if you say that there is audible benefit (though you’d have to prove it) but if external upsampling lowers the noise floor and reduces jitter then there is a benefit.

Whether or not jitter is an audible thing completely depends on the DAC and how much jitter rejection it has. It is not related to oversampling.

Noise floor of a DAC is rarely an issue.
Noise floor of a recording is much much higher and this will not change due to oversampling and determine the noise floor that is heard it is not related to oversampling.

 

[solderdude]

If filtering were perfect different filters and noise shapers would not measure or sound different.

Filters do not need to be technically perfect. And different measurements does not mean an audible difference in sound. An audible difference in sound, however, is always measurable.

 

[tuga]

Whether or not jitter is an audible thing completely depends on the DAC and how much jitter rejection it has. It is not related to oversampling.

Noise floor of a DAC is rarely an issue.
Noise floor of a recording is much much higher and this will not change due to oversampling and determine the noise floor that is heard it is not related to oversampling.

So upsampling and noise shaping do not affect the noise floor in the audio band?

 

[tuga]

Filters do not need to be technically perfect. And different measurements does not mean an audible difference in sound. An audible difference in sound, however, is always measurable.

I am not talking about filters in general but a brick wall below 22.05KHz

 

[Julf]

So upsampling and noise shaping do not affect the noise floor in the audio band?

No.

 

[Julf]

Yes

Evidence?

 

[tuga]

No.

Evidence?