Sample rates for audio DACs
I have been wondering why Audio DAC’s have so many sample rates , available and the quickest is 192kSamples
The max sample rate is 192kSamples wich is approx. 4,8 X Nyquist sample rate
I have had a thought that it might be because the 48k samples covering a continuous 20kHz tone with a amplitude determined in the 24bit is OK
But when you change the amplitude on a 20kHz very steep the pitch from a (like the splash pelvis
And the change is more like a square wave you need many harmonics to have a better reproduction of the sound and hence the 192kSamples would that be reason ?
(I assume the data available from the ADC should be equivalent in # of bit and samplerate otherwise it will only be the S/W controlling DAC and showing its interpolation )
Hello,
You are discussing something that has been argued for many years! The Nyquist frequency for 48kHz is 24kHz and it is 96kHz for a sampling rate of 192kHz so that is exactly 4x the frequency for 48kHz fs.
So at 24Khz there are only 2 sample points per 24kHz cycle. For 20kHz it will almost be the same, 2.4 samples a cycle. So some cycles it is 2 samples and every once in a while it is three samples. But, the level can be way off and the phase also can be way off depending on where the samples are taken during the waveform.
So by going up to 192kHz you increase the number of samples to 9.6 samples. So that will better capture the 20kHz signal.
Now I need to mention that your case of a 20kHz square wave needs to be examined a bit more closely. A 20kHz square wave has harmonics that are 3X, 5X, 7X etc.,... of 20kHz. This is far above the Nyquist frequency of 24kHz so either those harmonics will be filtered out or they will be aliased down into the audio band. So the 20kHz square wave will never be captured and should not be.
So the discussion is if you can hear the difference between a 20kHz square wave or a filtered 20kHz that is now a sine wave? I am of the camp that you can hear the influence of higher frequencies on lower frequencies that you can hear.
Others may chime in here to discuss this. Part of this is mathematical fact but part of this is perception which is difficult to quantify. Thus the controversy.
Dave T
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