How many bits, how fast, just how much resolution is enough?

[mansr]

If filtering is the same for everything, how Redbook sound better due filtering as gmgraves says? Maybe we can wait answer from gmgraves, I hope .

 

He said 16-bit data sounds better through a 24-bit capable DAC since it has superior filtering to a DAC limited to 16 bits. He did not say that 16-bit sounds better than 24-bit.

[mansr]

You misunderstand me, I think. A 24-bit DAC's filter doesn't perform differently when processing 16-bit/44.1 KHz material than it does when it is decoding 24-bit/96 or 192 KHz material, it handles 16-bit as if it were 24-bit. With 16-bit/44.1 KHz material, the sample rate (44.1 KHz) must roll-off very steeply above 22.5 KHz to satisfy the Nyquist theorem. Such so-called "brick wall" filters can cause problems like phase shift in the audible band. When a 16-bit/44.1 KHz source (such as a CD) is played on a DAC that can handle 24-bit/96 or 192 KHz files, the sampling frequency is much higher than 44.1 KHz by twice or even 4X (in a 192 KHz capable DAC). This moves the sampling rate far outside the 22.5 KHz bandwidth of a16-bit/44.1 KHz file (such as a CD). There are several different ways to do this, but the result is that the "Q", or steepness of the filter can be much more gentle, and therefore does not introduce the phase shift and other anomalies caused by steep, brick-wall filters required to get the audio signal down by at least -20 dB by the time the sampling frequency is reached (at least 2X the "Nyquest" frequency [or top frequency being quantized], in this case 22.5 KHz). I hope this clears up the confusion. It's a bit oversimplified as an explanation, but just remember that the further the DAC's sampling rate is from the highest frequency in which one is interested (again, 22.5 KHz for Red Book CD), the better the sound. Oh, yes, one other thing. 16-bit sounds better through a 24-bit DAC than it does through a 16-bit DAC due to the filtering employed, but also because no commercial 16-bit DACs have 16-bit linearity, just as no 24-bit DAC gas 24-bit linearity. BUT a 24-bit DAC does have 16-bit linearity (at least) which lowers quantization error of 16-bit material substantially. But I never said or inferred that 16-bit through a 24-bit DAC sounds better than 24-bit through the same DAC, which I believe you think I was saying.

Uh, I think you're confused. Any 44 kHz signal needs a sharp filter, even if the DAC is capable of higher sample rates.

[mansr]

The "gentle" filter I prefer is to convert the 44 kHz signal to DSD512 then 32 tap FIR followed by a gentle analog filter. Sounds great.

The upsampling needs a sharp (digital) filter or you'll get images starting at 22.05 kHz.

[mansr]

Does that not depend on whether or not up-sampling is used on the 44.1 KHz. Don't most modern 24-bit DACs do that? I see that I failed to make that distinction, in which case, mia culpa. Thank you for pointing that out Mansr!

 

The filtering is part of the upsampling. If not done, the higher-rate digital signal will contain images. This filtering is actually one of the main reasons for upsampling in the first place. It's much easier to create a sharp digital filter than an analogue one. A 2x upsampled (and thus digitally filtered) signal has essentially no content in the upper half of its frequency band, making construction of an adequate analogue filter much simpler.