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Non-oversampling delta-sigma DAC?
Non-oversampling delta-sigma DAC?
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Old 21st December 2016, 02:19 PM   #11
Ken Newton is offline Ken Newton  United States
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I've neglected to address an important point. Oversampling also opens up ultrasonic spectrum space for the SDM unit to relocate the quantization noise. The greater the oversampling ratio the more spectrum is opened and the less is the intrusion of the relocated noise in to the upper portion of the desired signal band. Without sufficient open (unused) spectrum the relocated quantization noise could significantly raise the signal band noise floor. The below link is to a nice graph on the dddac site that shows exactly that effect occurring. It shows a 40dB increase in the noise floor for a 44.1k sample rate by 20kHz, verus a 192k sample rate. I assume that the depicted sample rates are all without benefit of oversampling.

http://dddac.com/pictures/pics1794/t...92fs_large.png

Last edited by Ken Newton; 21st December 2016 at 02:30 PM.
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Old 22nd December 2016, 12:01 AM   #12
goodjingan is offline goodjingan
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i don't see oversampling is something bad. on the contrary it's a good thing. IMHO the evil is in the filters.

in this following experiment you'll see how different filters causing different phase problem and time smearing (ringing) which we may perceived as "digital sound". although it's done on music files using software and much more steep filters than used in delta sigma DACs, it shows us who's the bad guy

Ringing False: Digital Audio's Ubiquitous Filter Page 2 | Stereophile.com
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Old 22nd December 2016, 05:14 AM   #13
Ken Newton is offline Ken Newton  United States
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Quote:
Originally Posted by goodjingan View Post
i don't see oversampling is something bad. on the contrary it's a good thing. IMHO the evil is in the filters.
Oversampling is an integral aspect of the digital reconstruction filter's functioning.

Quote:
...in this following experiment you'll see how different filters causing different phase problem and time smearing (ringing) which we may perceived as "digital sound"...
You're touching on a very controversial area here. Sampling requires band limiting the desired signal. Because CD supports only just enough spectrum to carry the audio band it requires sharply band limiting the desired signal. It is the sharp band limiting which produces the infamously ringing filter impulse response. While sampling theory is fully satisfied with sharp band limiting there is not universal agreement as to the affect on human subjective perception using dynamic signals such as music.
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Old 23rd December 2016, 12:33 AM   #14
goodjingan is offline goodjingan
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Quote:
Originally Posted by Ken Newton View Post
there is not universal agreement as to the affect on human subjective perception using dynamic signals such as music.
you are correct. no wonder i feel like i'm not the only one. well, instead of opening that infamous can i better be a silent reader. lots of financial interests here
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Old 23rd December 2016, 01:16 AM   #15
Ken Newton is offline Ken Newton  United States
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Quote:
Originally Posted by goodjingan View Post
you are correct. no wonder i feel like i'm not the only one. well, instead of opening that infamous can i better be a silent reader. lots of financial interests here
No, no, please feel free to open any cans you wish to. Use this forum to express your opinions, to ask questions and to share your findings. No one knows everything, although, I suspect that one or two of us here would like everyone else to believe that they do. My view is that we are all here to both learn and to teach, depending on the topic and the participants on a given thread.

Last edited by Ken Newton; 23rd December 2016 at 01:29 AM.
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