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Why Hi-Resolution is needed for digital sources (Read 1563 times)
analogwave
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Why Hi-Resolution is needed for digital sources
03/04/18 at 16:42:10
 
[/color]Just found a great video explaining (for digital sources) why high-resolution audio is critical.

To give you a little back ground before you watch the video:

1) The Nyquist–Shannon sampling theorem establishes a sufficient condition for a sample rate that permits a discrete sequence of samples to capture all the information from a continuous-time signal of [color=#009900]finite bandwidth
, and that the sufficient sample-rate is twice the bandwidth (ex. a 24kHz bandwidth could be represented by a 48kHz sample-rate)

2) The key point here is "finite bandwidth", and that finite bandwidth is not possible with current filtering technology.  So the real world implementation of this theorem will introduce error into the signal if that signal is not perfectly bandwidth limited.

3) To help minimize the error introduced the sampling rate is increased (192 KHz, 384kHz, etc.) so that filters with a lower roll-off can be used.

In my opinion out of all the errors introduced by not being able to perfectly bandwidth limit the signal, the worst are: 1) phase error and 2) ringing artifacts (like pre-echo).  I think our ears are extremely sensitive to phase errors and pre-echo.  Especially pre-echo, because in the real world you can't hear a sound before it happens Smiley

The youtube video is titled "The truth about Nyquist and why 192 kHz does make sense"
Here is the link:
https://youtu.be/geaoEt-9V-w

Also, this comment by Zachary Doering about the video brings up some excellent points:

[/color]"I think part of the discussion that needs to really be explained is the effect of band limiting in both the digital and analogue domain, any band limiting anywhere will causing ringing artifacts, any cable and equipment you use will do this as well. This is why I find double blind tests of audio not truly scientific to disprove high-resolution. If you band limit a cable to 10k due to capacitance that will have an audible effect and therefore you really are not isolating all variables scientifically. The provenance of the signal is no longer intact.

When I hear Pro-Audio people, or people like Monty, tell me they cannot hear the difference, I would want to ask them how many looms of cabe and what kind of monitors are you using? what are their crossover freqs? Any of those things can introduce tons of ringing artifacts that will make high res compromised, or really any signal.

To add to your point Hans, I remember dCS had a white paper on their website some time back, that explained what extreme band limiting in the digital domain did, and they showed it caused phase and amplitude shift, they had snapshots of it on oscilloscopes. This is known in physics as the Gibbs Phenomenon. It is never explained by the apologists of just sampling at nyquist. Any filtering you do will cause a ripple effect in the audio much like throwing a rock in a pond. Humans can hear the harmonics of fundamental frequencies way above 20k and the phase and ringing artifacts smear in the time domain. All of these things are important. If high order harmonics were not important then, for example, the type of piano or guitar you use and how it resonates would be inconsequential because they are all generating the same fundamental frequencies, but as any musician will tell you, it does matter. Why? due to the distribution of how those frequencies sit, and all of this information happens in the upper end of the frequency range.

Personally I have heard the effects of high sample rate and DSD, but it does require a controlled set up, actually I found that tube gear demonstrates it the most due to it's high slew rate, and when I managed a high end store, we had some tube preamps that could go to 100k and high sample rate was very audible on those especially DSD. I also had a CD player that had a band limit of 80k and could select the CD layer at 16/44.1k and the SACD layer, I was even able to demonstrate to audiophiles who didn't believe in DSD that it made a difference it was very audible on a non band limited player.

In short I think the people who maintain there is no difference either have never heard live music or lack the equipment and discernment to hear the difference, because the changes are very audible even to the un-initiated on the right system.  

Simply put Nyquist is sufficient to prevent aliasing, but not sufficient to portray real life, and we are after it sounding like real life, not to just no longer have aliasing artifacts.

To use another analogy 24fps will allow the human eye to perceive motion in still pictures, but it doesn't look as if we are actually seeing through a window in real life. The only thing that can approach that is a high resolution screen at a high frame rate, and that is what we want with audio."


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analogwave
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Re: Why Hi-Resolution is needed for digital sources
Reply #1 - 03/24/18 at 17:24:42
 
This is also why wide bandwidth tube amplifiers are necessary for accurately reproducing sound:

1) they can pass through the higher order harmonics of the fundamental frequency
2) and they maintain the phase and amplitude of those harmonics

And it is this harmonic structure that makes music sound more life like.

The comment in the previous post makes this point too:

"I remember dCS had a white paper on their website some time back, that explained what [color=#0000ff]extreme band limiting in the digital domain did, and they showed it caused phase and amplitude shift, they had snapshots of it on oscilloscopes. This is known in physics as the Gibbs Phenomenon. It is never explained by the apologists of just sampling at nyquist. Any filtering you do will cause a ripple effect in the audio much like throwing a rock in a pond. Humans can hear the harmonics of fundamental frequencies way above 20k and the phase and ringing artifacts smear in the time domain. All of these things are important. If high order harmonics were not important then, for example, the type of piano or guitar you use and how it resonates would be inconsequential because they are all generating the same fundamental frequencies, but as any musician will tell you, it does matter. Why? due to the distribution of how those frequencies sit, and all of this information happens in the upper end of the frequency range.

Personally I have heard the effects of high sample rate and DSD, but it does require a controlled set up, actually I found that tube gear demonstrates it the most due to it's high slew rate, and when I managed a high end store, we had some tube preamps that could go to 100k and high sample rate was very audible on those especially DSD. I also had a CD player that had a band limit of 80k and could select the CD layer at 16/44.1k and the SACD layer, I was even able to demonstrate to audiophiles who didn't believe in DSD that it made a difference it was very audible on a non band limited player.

In short I think the people who maintain there is no difference either have never heard live music or lack the equipment and discernment to hear the difference, because the changes are very audible even to the un-initiated on the right system."[/color]

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orangecrush
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Re: Why Hi-Resolution is needed for digital sources
Reply #2 - 03/24/18 at 17:53:45
 
Thanks for this. Much is over my head, but I am taking a step backward with my digital front end. I have become very sensitive to any processing of any kind finding it reduces the perceived dynamic range of the music. While high res files sound great, I am listening mostly to Tidal through Roon. Any time I have tried to up sample, it has been disappointing. Compressed is what I hear.

So now, I am going to try a ANK DAC 4.1 LE in the pursuit of getting the most out of Red book which is 95% of what I listen too. No digital processing, no digital filter, tube output with high bandwidth output c-core transformers. And of course tube regulated and rectified power supply.  

I have talked to many who already have done this and they all are stunned by the restored, “perceived” dynamic range of the music. One individual is adandoning his Hugo Dave after hearing the difference. Emotional connection without losing transparency or resolution.  

I think native DSD sounds amazing, but upsampling redbook to DSD is not the holy grail. I think up sampling redbook to DSD stems from the desire for people to remove the digital glare from the digital filters.  In doing so, you actually remove details of the music. It’s ‘over smoothed’ to my ears.  Lacking emotion. Going backward and stripping out those digital filters is the real antidote. But granted it is leap of faith.  And after I evaluate my my new DAC, I might change my mind. Smiley

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Lon
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Re: Why Hi-Resolution is needed for digital sources
Reply #3 - 03/24/18 at 18:17:32
 
orangecrush wrote on 03/24/18 at 17:53:45:
Thanks for this. Much is over my head, but I am taking a step backward with my digital front end. I have become very sensitive to any processing of any kind finding it reduces the perceived dynamic range of the music. While high res files sound great, I am listening mostly to Tidal through Roon. Any time I have tried to up sample, it has been disappointing. Compressed is what I hear.

So now, I am going to try a ANK DAC 4.1 LE in the pursuit of getting the most out of Red book which is 95% of what I listen too. No digital processing, no digital filter, tube output with high bandwidth output c-core transformers. And of course tube regulated and rectified power supply.  

I have talked to many who already have done this and they all are stunned by the restored, “perceived” dynamic range of the music. One individual is adandoning his Hugo Dave after hearing the difference. Emotional connection without losing transparency or resolution.  

I think native DSD sounds amazing, but upsampling redbook to DSD is not the holy grail as many think.


Looks like a great DAC, let us know what you think if it enters your system.

I don't know about  some of these conclusions. In my system dynamics are almost off the hook, so I'm not sure my PS Audio DSD and its conversion of all sources to DSD64 is restricting anything but there certainly are other factors in my system (ZTPRE, ZBIT, ZROCK2).
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orangecrush
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Re: Why Hi-Resolution is needed for digital sources
Reply #4 - 03/24/18 at 18:53:44
 
Hey Lon, yes, I am taking a big gamble. No way to audition it. But if it lives up to what others experienced (and also the theories behind it), who I trust, it will be my missing link. My system is built on lifetime components. And I want a lifetime DAC that never needed upgrading.  The only upgrade I will ever need to make is the network source. The Allo Digione is just a marvel for peanuts.

So I can feed the ANK DAC with the lowest jitter SPDIF signal possible by current standards.

I really think all these “additional boxes” were adding to our systems are to correct something that is just broken. Fix the problem and remove all the extra boxes, ICs and DSP.  Again, I could be wrong! Time will tell. Smiley

It’s actually Decware that motivated me to begin researching the problem with DSP and Digital filters.  There are awesome studies and research done in the early eighties, especially in Japan.  Every time I see a new box that Steve releases to fix a problem I started to look at why audio is so messed up today. There is no way in hell I am going to introduce multiple paths and ICs in my signal chain. You fix one problem and it creates another.  I tried one of these boxes, and it just introduces more noise and took a layer of resolution away.

I believe Lon you have the patience to make it all work and sound amazing. And that’s why this is a hobby.  

But what if there is another way?  A more zen way like Decware started out with. Short signal paths. A simple path from digital to analog mainting the weight, frequency extension and all the bandwidth that the human gear can hear?

If this pans out for me, then I feel it’s the perfect fit to the philosophy of low powered amps driving HE single driver speakers. Again, this could all go terribly wrong!



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Lon
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Re: Why Hi-Resolution is needed for digital sources
Reply #5 - 03/24/18 at 19:24:42
 
Well, I hope that your journey takes you where you want to go with a source that doesn't need upgrading. it's interesting that my DSD gets it's OS upgraded and each upgrade is an improvement on a sound I was very happy with, so I don't see a danger to upgrades!

And also interesting that I was so adamant about keeping things as simple as possible, but adding my "Z Amigos" has both given me MORE transparency and LESS noise. And neither would matter if they weren't giving me BETTER sound. So I'm on the final leg of my different journey. . . the Anniversary Monoblocks should ice the cake for me and I'll be set for some time  (my guess).
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orangecrush
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Re: Why Hi-Resolution is needed for digital sources
Reply #6 - 03/24/18 at 20:13:42
 
That’s just it. Every time we upgrade our DACs, or the software, and pursue higher and higher numbers, it’s supposed to another 20% better each time, I just don’t see the cumulative net gain. We should have a 1000 times better audio by now according to this philosophy.

There are many ways to achieve what a person needs from their audio and musical experience, but for me its going back to a purist system where emotional engagement triumphs at the expense of “hifi”.
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orangecrush
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Re: Why Hi-Resolution is needed for digital sources
Reply #7 - 03/29/18 at 23:07:43
 
Just thinking more about my less then stellar experiences with the ZStage and Zbox.

I think he biggest difference is when you are using very high efficiency speakers. My speakers are 101 db-spl 1w, 1m. My room is very quiet, and my power and cabling helps achieve a very low noise floor. I hear absolutely no noise or hiss even with my ear right against the speaker. The addition of the Stage and Zbox added noise and hiss which was not acceptable for me.

But, I don't think you would notice that much on a 92 db-spl speaker. But is you did hear a tiny increase, it would be much more on my speakers.
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Lon
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Re: Why Hi-Resolution is needed for digital sources
Reply #8 - 03/30/18 at 00:00:49
 
Sorry about the noise and hum issues as I know that can be very distracting. I did have a hum issue when I added the ZROCk2 but on investigation that was a result of the cable coaxial and I added a filter between a cable from the wall and a cable to the DVR and the hum was gone. Also I'm using balanced cabling from all sources to the ZTPRE and from there to the ZBIT. And the ZTPRE has a "no hum circuit" within (don't know anything about how it's constructed etc.) that really DOES work. I don't have any noise or hum to worry about, but then I don't have very high-efficiency speakers either.
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analogwave
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Re: Why Hi-Resolution is needed for digital sources
Reply #9 - 03/31/18 at 20:53:09
 
I've been trying to think of a good analogy to describe how filtering can impact sound and I keep coming back to water.  Steve often uses water analogies to explain complex audio concepts -which always creates a clear picture in my mind.  So here it goes...

Imagine an olympic swimming pool 50 meters long and 10 lanes wide.  Let's say lane 1 is the audio signal for humans, 20Hz to 24kHz to keep it simple, lane 2 (48kHz) is for dog lovers, lane 3 (96kHz) is for cat lovers, lane 4 (192kHz) is for dolphins, lane 5 (384kHz) is for robots, and lanes 6-10 (768kHz to 12,288kHz) for UFO landings, outer-space, dark matter, etc.  Your noise floor would be determined by how calm the water is, so ideally the pool would look like glass and you would be able to clearly see your undistorted reflection.

Now for your audio system design (Source/Amp/Cables/Speakers) the lane dividers would be the filters.  So you have to decide where you want to put the lane divider (and for this analogy the lane divider will be yellow rubber ducks strung together by steel cable).  So for a low bandwidth design we would put the lane divider at lane 2, and for a high bandwidth design we would put the lane divider out past lane 5.

The 50 meter length of each lane would be your audio system signal path from the source (the start line) all the way out through your speakers to your ears (the finish line at meter 50).  For this analogy we'll assume the audio source is perfect -but really we should consider, as part of the signal path, how the audio signal source was captured, recorded and mastered too.

Now we need to pass our audio signal through lane 1 of the pool.  Let's use the familiar pebbles in a pond analogy for the audio signal.  So the goal for the audio system would be to only have pebbles as the source of the ripples in the water.  So in our low bandwidth design, the lane 2 divider would have strong feedback ripples bouncing off the rubber ducks back onto our source ripples.  In the high bandwidth design the source ripples would have to cross over 5 lanes before they bounced of the rubber ducks and then have to travel back another 5 lanes to interfere with the source ripples.

We would want straight lane dividers too, so our lane dividers (filters) would all need to maintain the same bandwidth from start to finish.  For example, if one component of your audio system compressed the bandwidth down to lane 2 at any point along the 50 meter length of the lane then your audio signal would once again have strong interference because the feedback ripples coming of the rubber ducks would be much closer to your lane 1 source ripples.
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