WASAPI and bit depth question

[audiventory]

4 hours ago, Miska said:

When you go from 16-bit to 24-bit (or 32-bit) by zero-padding, the result is still considered bit-perfect.

 

In the digital domain it is bit perfect. But for DAC distortions it may be matter.

Because DAC may be buit by cascade scheme (group bits feed separate sigma delta modulators). As rule, it is fairly for any PCM DAC.

So sound may depend on zero-padding size. Though it is very subtle difference.

[audiventory]

19 hours ago, Miska said:

The internal DSP pipeline on delta-sigma DAC chips is 24- or 32-bit, so if you input 16-bit it is zeropadded the same. In addition for PCM inputs you have digital filters first (unless you go at 352.8/384k input rates) that will produce 24/32-bit output before feeding the modulator. XMOS USB interfaces use 32-bit sample format anyway. Some others use 24-bit.

 

On 06.10.2017 at 4:22 AM, audiventory said:

Because DAC may be buit by cascade scheme (group bits feed separate sigma delta modulators). As rule, it is fairly for any PCM DAC.

 

DSP and USB is not matter in context of the discussion. The issue placed in analog part of the DAC.

 

I meant cascade scheme. Me seems, I watched schemes, assembled from several sigma-delta modulators. But now I can't found example and, possibly, I mistaken in my post.

 

May be "multi level sigma-delta modulator" more correct term, than "cascase"?

 

In this case shifted 16 bit signal may don't touch lower levels of the modulator (DAC's cascades that generate the levels). I can suppose, that each level have own error.

 

Thus total error may be different if different level kits (all or upper only) are used.

Of course result depend on number output bits of the modulator.

 

I just looked for block diagrams of modern DAC chips. Looks like, there used single sigma-delta modulator per all bits (for block diagrams that I found). But I don't know exactly multilevel or not sigma-delta modulator there.

 

Unfortunatelly, measurements of pair / ten DAC show us how work these 2 / 10 items. It cannot be used as claim base for all cases. It is need to know exactly that inside DAC device and DAC chip for correct result interpretation.

 

 

 

[audiventory]

1 hour ago, Miska said:

Since those have at most 65-levels equivalent of 6-bits in two's complement it doesn't make sense in this scope.

 

If I understand correctly, each bit have own reference voltage. Error of the voltage can cause non-linear distortions.