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Old 10th April 2012, 05:58 PM   #271
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Quote:
Originally Posted by Ken Newton View Post
I'm still interested to read your answer to the question I asked you earlier. Did I miss your reponse? I'll repeat it here:

"Let me ask you a question, if the information encoded on a CD is time-domain sensitive (i.e., music), does the digital sinc filter's time-domain response ("ringing") distort that information? Be careful in your answer, recall that you've already said that the system having the higher distortion is definitionally, the more colored."

To be clear, I'm asking specifically about DAC impulse response. This question is distinct from that of DAC phase response. All linear phase FIR interpolation filters feature, guess what, linear phase, even though their time-domain (impulse) responses can vary dramatically. The now common practice of including a linear phase digital filter with fast and slow transistion band options, such in the T.I. PCM179x series DACs, exemplify that fact.
They have "slow" filter options to reduce the group delay through the filter for low-latency pro audio applications, not to satisfy a group of people who believe they prefer a worse-performing digital filter.
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Old 10th April 2012, 06:24 PM   #272
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Originally Posted by chris719 View Post
They have "slow" filter options to reduce the group delay through the filter for low-latency pro audio applications, not to satisfy a group of people who believe they prefer a worse-performing digital filter.
You appear to have totally missed the point of my question. I didn't ask why T.I. included these two filter options. I merely cited those T.I. DAC+DF chips as examples which demonstrate the distinction between FIR filter phase response and impulse response. My question was about the implications of sinc filter impulse response, with respect to time-domain sensitive information content. Now that you should be clear what the question was, perhaps you also would care to take a shot at addressing it?
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Old 10th April 2012, 06:48 PM   #273
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Originally Posted by bbggg View Post
If something was present in the original recording, how can it be artificial? In English this is a non sequitur. In Latin as well.
Exactly.
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Old 11th April 2012, 12:33 AM   #274
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Originally Posted by Ken Newton View Post
You appear to have totally missed the point of my question. I didn't ask why T.I. included these two filter options. I merely cited those T.I. DAC+DF chips as examples which demonstrate the distinction between FIR filter phase response and impulse response. My question was about the implications of sinc filter impulse response, with respect to time-domain sensitive information content. Now that you should be clear what the question was, perhaps you also would care to take a shot at addressing it?
I understand the pre-ringing bothers you, but what kind of band-limited signals do you play through your DAC on a daily basis?

I don't have any studies to reference but I'd expect the ringing to be inaudible myself.

Many albums you are listening to through your NOS DAC have probably been passed through linear phase SRC in the studio.
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Old 11th April 2012, 01:17 AM   #275
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Originally Posted by chris719 View Post
I understand the pre-ringing bothers you, but what kind of band-limited signals do you play through your DAC on a daily basis?

I don't have any studies to reference but I'd expect the ringing to be inaudible myself.

Many albums you are listening to through your NOS DAC have probably been passed through linear phase SRC in the studio.
Whether I feel pre-ringing bothers me, or not, you do agree that there is distortion of the time-domain waveform via typical CD standard recording/playback, and that the only question is whether that distortion is audible?
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Old 11th April 2012, 06:54 AM   #276
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I think the only answer to the first question can be "yes". The impulse is not recreated exactly the same as the original, so there must be distortion.

The second question is much harder to answer. The "bad" measurements of a NOS DAC don't seem to be all that correlated to the sound quality, but no doubt the same thing goes for "bad" measurements of OS on impulse response... If they were, we'd have gone one way or the other and never looked back. It may seem we have done so since OS is the (almost) universally agreed upon method, but that may just be the result of gathering enough followers.
The people that have heard a good implementation of NOS are beginning to question the validity of (some of the) assumptions OS is based upon.

Last edited by jitter; 11th April 2012 at 07:00 AM.
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Old 11th April 2012, 11:29 AM   #277
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Originally Posted by jitter View Post
I think the only answer to the first question can be "yes". The impulse is not recreated exactly the same as the original, so there must be distortion.

The second question is much harder to answer. The "bad" measurements of a NOS DAC don't seem to be all that correlated to the sound quality, but no doubt the same thing goes for "bad" measurements of OS on impulse response... If they were, we'd have gone one way or the other and never looked back. It may seem we have done so since OS is the (almost) universally agreed upon method, but that may just be the result of gathering enough followers.
The people that have heard a good implementation of NOS are beginning to question the validity of (some of the) assumptions OS is based upon.
Yes. The fundamental technical "fault" of the CD medium for music, as I see it, is that while CD can accurately capture the full frequency-domain components of music, it does so at the expense of time-domain distortion. This seems the only plausible explanation for why NOS sounds more natural than OS (a generalization, I know). NOS provides a slightly curtailed high frequency repsonse (-3.16dB@20kHz) in exchange for a perfect impulse (time-domain) response.

There isn't any inherently greater in-band distortion via NOS. The greater ultrasonic image replication content of NOS is above the audio band, so, unless the post D/A amplification chain is prone to significant IMD, there won't be any greater in-bamd distortion for NOS compared to OS.
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Old 11th April 2012, 11:43 AM   #278
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Quote:
Originally Posted by Ken Newton View Post
This seems the only plausible explanation for why NOS sounds more natural than OS (a generalization, I know). NOS provides a slightly curtailed high frequency repsonse (-3.16dB@20kHz) in exchange for a perfect impulse (time-domain) response.
Yet the fly in the ointment for this hypothesis (ISTM anyway) is the one chris719 has already hinted at - the perfect time domain performance of NOS is just going to faithfully reproduce the linear phase, pre-ringy time domain performance of the ADC (and potentially ASRC or whatever else got put in the signal path). So why would that last filter (present or absent in the DAC) make all the difference between NOS and OS when there's bound to be at least one non-optimal filter in line prior to it?
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Old 11th April 2012, 11:57 AM   #279
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Originally Posted by abraxalito View Post
Yet the fly in the ointment for this hypothesis (ISTM anyway) is the one chris719 has already hinted at - the perfect time domain performance of NOS is just going to faithfully reproduce the linear phase, pre-ringy time domain performance of the ADC (and potentially ASRC or whatever else got put in the signal path). So why would that last filter (present or absent in the DAC) make all the difference between NOS and OS when there's bound to be at least one non-optimal filter in line prior to it?
This is VERY good question.
ASRC does horrors to the signal and I try to avoid it like pest. A lot of stuff is registered at 88.2k which is probably better than 96k downsampled to 44.1.
I guess filters applied digitally when mastering are not that damaging compared to the aliasing filter done at the DAC?
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Old 11th April 2012, 06:52 PM   #280
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Originally Posted by abraxalito View Post
Yet the fly in the ointment for this hypothesis (ISTM anyway) is the one chris719 has already hinted at - the perfect time domain performance of NOS is just going to faithfully reproduce the linear phase, pre-ringy time domain performance of the ADC (and potentially ASRC or whatever else got put in the signal path). So why would that last filter (present or absent in the DAC) make all the difference between NOS and OS when there's bound to be at least one non-optimal filter in line prior to it?
That seemingly contradictory fact helped lead me to the hypothesis I had suggested in the final several paragraphs of post #120 here: Metrum Octave Dac - What are the Chips used

I suspect that much of the subjectively annoying aspects of CD audio stems from the dynamic interaction of the MULTIPLE (at least two) sinc filter responses across the recording/playback chain. Remove either the ADC sinc response via apodising, or remove the DAC sinc repsonse via NOS and, viola', much more natural sounding reproduction results. I would add that while eliminating one of those two (at the least) sinc responses in the chain substantially improves the sound, it may also be that removing BOTH would improve the sound to it's ultimate point. Something which could be done using high sample rate audio.
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Last edited by Ken Newton; 11th April 2012 at 07:20 PM.
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