John Atkinson: Yes, MQA IS Elegant...

[Shadders]

Hi,

OK - is MQA Ltd stating that ADC's filters introduce ringing even though the energy at 80kHz to 96kHz (fs=192kHz) is zero ?

 

I assume the answer is that there is NO ringing in the recording.

Regards,

Shadders.

[esldude]

37 minutes ago, Shadders said:

Hi,

OK - is MQA Ltd stating that ADC's filters introduce ringing even though the energy at 80kHz to 96kHz (fs=192kHz) is zero ?

 

I assume the answer is that there is NO ringing in the recording.

Regards,

Shadders.

And other than a very few extended response microphones the energy left at 40 khz to 48 khz in 96 khz sampling is though not zero very low in level.  There isn't anything to do much of any ringing.  Plus at those frequencies we aren't hearing that.  At 96 khz and even more so at 192 khz sample rates the microphones have implemented an uncontrolled slow rolloff filter. 

[Shadders]

1 minute ago, esldude said:

And other than a very few extended response microphones the energy left at 40 khz to 48 khz in 96 khz sampling is though not zero very low in level.  There isn't anything to do much of any ringing.  Plus at those frequencies we aren't hearing that.  

Hi,

The statement was semi-rhetorical.  ?

 

There is no information at these frequencies, and so the claimed ringing does not exist in the ADC.

 

Also, the ringing is directly proportional to the power level at the relevant frequency in the audio, so the ringing is non-existent at the 80kHz to 96kHz level (again).

 

JA stated : "That unless the user of an A/D converter is prepared to accept the possibility of some aliased image energy in order to use an antialiasing filter that preserves the time-domain behavior of the original analog signal, the resultant digital data will have sinc-function content at the Nyquist frequency accompanying every musical transient. "

 

The filters used are linear phase - so why would there be a problem with time domain behaviour ?. No smearing (dispersion) as claimed. (question to JA)

 

The only issue is the downsample/decimation from 192kHz to 44.1kHz. But as mansr showed, that the effect of ringing is significantly reduced by using the kaiser window method for filter generation to below -200dB. This is a linear filter too - no dispersion.

 

There are transient effects, but these are not smearing issues - just noise added to the signal for those filters that have a higher stop band - such as -60dB (TI PCM5252) to -100dB. The TI PCM5252 has multiple filters where one is asymmetric or minimum phase. They seem to be similar to those used by MQA. The PCM525 also has a mini DSP on board.

 

Most DAC IC's allow the use external filters - so in any event, you can design your own - to exceed the DAC IC inbuilt filters.

 

So for CD playback, ringing is not an issue. For high resolution - ringing is still not an issue. Neither is smearing - it does not exist in the audio chain.

 

Regards,

Shadders.

[adamdea]

2 hours ago, John_Atkinson said:

In the context of testing audio components, this is an enormous subject. All I can suggest is that you read the tutorial articles in the free on-line archives at the Stereophile website.

 

John Atkinson

Editor, Stereophile

 

This is a an obfuscation- you have explicitly  claimed that the results your test signal incontrovertibly led to a specific conclusion about musical signals. 

You have quite obviously overreached yourself in this claim. It might be that a more moderately worded claim would hold some water, and the smart thing to do might be to row back slightly.

[Jud]

2 hours ago, Shadders said:

The filters used are linear phase - so why would there be a problem with time domain behaviour ?. No smearing (dispersion) as claimed. (question to JA)

 

Just for clarification - In all I have read, "smearing" in the time domain and dispersion are two different things.

 

I have seen "smearing" and time domain distortion discussed in connection with ringing, especially pre-ringing, which a minimum phase filter with a slow rolloff is designed to avoid.  (If the rolloff begins too close to the "Nyquist limit," and/or does not cut sufficiently, the filter will be "leaky" and allow aliasing and imaging.)

 

A minimum phase filter is said to be dispersive (and thus has group delay), since the time for each frequency to pass through the filter is different.  I have not seen this written about either in terms of smearing or in terms of time domain distortion.  (It may be a time domain distortion, I just haven't seen it written about that way.)

[vl]

57 minutes ago, Jud said:

 

Just for clarification - In all I have read, "smearing" in the time domain and dispersion are two different things.

 

I have seen "smearing" and time domain distortion discussed in connection with ringing, especially pre-ringing, which a minimum phase filter with a slow rolloff is designed to avoid.  (If the rolloff begins too close to the "Nyquist limit," and/or does not cut sufficiently, the filter will be "leaky" and allow aliasing and imaging.)

 

A minimum phase filter is said to be dispersive (and thus has group delay), since the time for each frequency to pass through the filter is different.  I have not seen this written about either in terms of smearing or in terms of time domain distortion.  (It may be a time domain distortion, I just haven't seen it written about that way.)

 

We may be talking about two kinds of smearing here.

 

Case 1

 

Take an impulse signal that is band limited to the audio range (meaning the spike is not infinitely thin in time) and pass it through a linear phase brick wall filter set at 25 KHz.  The signal at the output of the filter will be practically the same as the input signal as the linear phase filter has constant group delay (meaning all frequencies are delayed by the same amount of time through the filter).  

 

Pass this same impulse signal through a minimum phase brick wall filter.  Different frequencies will be delayed by different amounts of time as the minimum phase filter has variable group delay.  The signal at the output of the filter will spread out in time according to frequency.  This temporal spear should be audible as it is in the audio range.

 

Please note that since the signal is band limited to below the audio range (about 20 KHz), there will not be brick wall filter ringing.

 

Case 2

 

Take an impulse signal that is not band limited (has infinite band width) and pass it through the same linear phase filter.  Filter ringing at 25 KHz will be visible.  

 

Take the same signal and pass it through the same minimum phase filter.  Filter ringing at 25 KHz will be visible.  

 

Some people may want to call this ringing smearing of the impulse signal.  It occurs at the filter cutoff frequency.  It should be inaudible as it is above the audio range.  Your dog may hear it.

[Fokus]

9 hours ago, John_Atkinson said:

If the original data were captured at 2Fs and or 4FS rates, then the sample-rate converter used to prepare a CD master will introduce ringing at the new Nyquist frequency of 22.05kHz with every musical transient.

 

Decoding these correctly band-limited digital data with a conventional sinc-function reconstruction filter will replace this ringing with its own, again at Nyquist, with every transient. A slow-rolloff reconstruction filter will not ring but will preserve the Nyquist-frequency ringing in the original data.

 

That is true, but in your article you did not demonstrate this because your SRC did not generate a correctly band-limited signal, due to it being half-band.

This preserved signal at exactly Fs/2, thus making the (also half-band) DAC also ring at Fs/2, violating the sampling theorem. (Note: this new ringing is added, it does not replace the SRC's.)

 

This need not be the case. If you used an SRC that fully reached its stopband slightly before Fs/2 the DAC would not ring. The only ringing would be the one of the SRC.

And if you feel bad about this ringing, you can ameliorate it by giving the SRC a sufficiently-wide transition band. While this is somewhat tight for CD rate, it is better at 48kHz, and totally unproblematic at higher rates.

 

Try it.

 

This might even result in an article worth reading.

 

 

 

 

 

[Fokus]

7 hours ago, adamdea said:

Of course. But the claim that the results led to an incontrovertible conclusion about every actual musical event of a particular type is novel. You know this, why play act?

 

The synthetic nature of the signal is not the problem. As said before, one could take this signal and write a symphony for it.

 

The issue is 1) a far too complex approach for proving something very simple, and 2)  the employment of an improper SRC or failing to note a key property of that SRC and how this invalidates the 'proof'.

 

[Fokus]

2 hours ago, vl said:

The signal at the output of the filter will spread out in time according to frequency.  This temporal smear should be audible as it is in the audio range.

 

Not necessarily. While really not very well documented (interest seems low, wonder why?) there are audibility limits for non-linear phase distortion. And audibility tends to be low at the extremes of the audible region. (Which makes sense ...)

[Shadders]

5 hours ago, Jud said:

 

Just for clarification - In all I have read, "smearing" in the time domain and dispersion are two different things.

 

I have seen "smearing" and time domain distortion discussed in connection with ringing, especially pre-ringing, which a minimum phase filter with a slow rolloff is designed to avoid.  (If the rolloff begins too close to the "Nyquist limit," and/or does not cut sufficiently, the filter will be "leaky" and allow aliasing and imaging.)

 

A minimum phase filter is said to be dispersive (and thus has group delay), since the time for each frequency to pass through the filter is different.  I have not seen this written about either in terms of smearing or in terms of time domain distortion.  (It may be a time domain distortion, I just haven't seen it written about that way.)

Hi Jud,

If you examine the link :

http://www.aes.org/tmpFiles/elib/20180906/17501.pdf

The AES MQA paper on page 3 states blur and dispersion are the same thing :

 

"It is now widely accepted that one key benefit of higher sample rates isn’t conveying spectral information beyond human hearing, but the opportunity to tackle the dispersive properties of brick-wall filtering"

 

"When considering the frequency and time responses of an end-to-end distribution channel, we must bear in mind that time dispersion or ‘blur’ can build up through a cascade of otherwise blameless components "

 

Again, the ringing, if it occurs is directly proportional to the power in the signal at the specific frequency, and the ringing is always less than the power at the specific frequency. So for a 22.05kHz cut off frequency, then this ringing will be small for a lower stop band filter such as a -60dB stop band (linear phase). The ringing will be non-existent for a filter with a stop band of -200dB or greater. These type of filters are easy to implement and when used in the recording chain, a CD will not contain ringing.

 

The MQA paper refers to smearing as reference [57] on page 6. In the context of the MQA document, it only refers to smearing in terms of the capability of human hearing being able to discriminate between signal with 7uS difference. It does NOT state temporal blur is smearing. It NEVER states what smearing is in terms of the issues that MQA is to solve. It only discusses temporal blur == dispersion.

 

Smearing seems to be made up issue which is discussed in respect to MQA, but MQA have never stated it in their publication as an issue.

 

Regards,

Shadders.

 

 

[Fokus]

58 minutes ago, Shadders said:

The ringing will be non-existent for a filter with a stop band of -200dB or greater.

 

If this were true then Sinc(x) itself would not ring.

 

[Shadders]

6 minutes ago, Fokus said:

 

If this were true then Sinc(x) itself would not ring.

 

Hi,

My mistake, the ringing is reduced but only slightly - from -100dB stop band to -300dB stop band. The ringing is still proportional to the power level at the cut off frequency.

 

It was the other effects which was the transient noise which was reduced, where for a -100dB stop band the transient noise was at 1e-6, and for the -300dB stop band the transient noise was at 1.8e-16

 

Regards,

Shadders.

[mansr]

4 hours ago, Fokus said:

That is true, but in your article you did not demonstrate this because your SRC did not generate a correctly band-limited signal, due to it being half-band.

This preserved signal at exactly Fs/2, thus making the (also half-band) DAC also ring at Fs/2, violating the sampling theorem. (Note: this new ringing is added, it does not replace the SRC's.)

 

This need not be the case. If you used an SRC that fully reached its stopband slightly before Fs/2 the DAC would not ring. The only ringing would be the one of the SRC.

And if you feel bad about this ringing, you can ameliorate it by giving the SRC a sufficiently-wide transition band. While this is somewhat tight for CD rate, it is better at 48kHz, and totally unproblematic at higher rates.

 

Try it.

 

This might even result in an article worth reading.

I already wrote that article: https://troll-audio.com/articles/filter-ringing/

[mansr]

7 hours ago, Jud said:

Just for clarification - In all I have read, "smearing" in the time domain and dispersion are two different things.

It should be called Heisenberg smearing since it seems that whatever quantifiable phenomenon you're talking about, it is always said to be something else.

 

7 hours ago, Jud said:

I have seen "smearing" and time domain distortion discussed in connection with ringing, especially pre-ringing, which a minimum phase filter with a slow rolloff is designed to avoid.  (If the rolloff begins too close to the "Nyquist limit," and/or does not cut sufficiently, the filter will be "leaky" and allow aliasing and imaging.)

 

A minimum phase filter is said to be dispersive (and thus has group delay), since the time for each frequency to pass through the filter is different.  I have not seen this written about either in terms of smearing or in terms of time domain distortion.  (It may be a time domain distortion, I just haven't seen it written about that way.)

How about this: https://troll-audio.com/articles/linear-and-minimum-phase/

[Jud]

20 minutes ago, mansr said:

How about this: https://troll-audio.com/articles/linear-and-minimum-phase/

 

Not sure how proud you want to be about helping to bring what I think may be a relatively new usage to the term "smearing."   The home audio market is already full of terms that require explanation (I've encountered many people on the forum convinced their DACs use good "oversampling," as opposed to evil "upsampling").

[mansr]

5 minutes ago, Jud said:

Not sure how proud you want to be about helping to bring what I think may be a relatively new usage to the term "smearing." 

I only used the word once.

[Jud]

1 hour ago, mansr said:

I only used the word once.

 

Note the winkie (which got cut off when you quoted me).

[wgscott]

3 hours ago, Jud said:

 

Note the winkie (which got cut off when you quoted me).

 

Omitting the Winkie of Absolution alters the character of the quoted content without changing its MD5sum.

[vl]

9 hours ago, Fokus said:

 

Not necessarily. While really not very well documented (interest seems low, wonder why?) there are audibility limits for non-linear phase distortion. And audibility tends to be low at the extremes of the audible region. (Which makes sense ...)

 

I shall share my own experience.  This is not to indicate the whole world is like my experience.  My DAC is the Auralic Vega.  It has a choice of linear and minimum phase reconstruction filters.  I can hear clarity decrease in upper treble when the minimum phase filter is in use.  In contrast the linear phase filter sounds more like the real thing.  This observation is made with classical symphonic music, without percussion.  

 

My system is good enough that when I listen to a CD, I can tell which CD was originally recorded on tape (even those recorded in the '70s with Dolby A) and which were recorded digitally.  The better digital recordings are far superior to analog tape, despite the ringing and dispersion that may exist with the CD format.

[Ralf11]

https://en.wikipedia.org/wiki/Schmear

[adamdea]

22 hours ago, Fokus said:

 

The synthetic nature of the signal is not the problem. As said before, one could take this signal and write a symphony for it.

 

The issue is 1) a far too complex approach for proving something very simple, and 2)  the employment of an improper SRC or failing to note a key property of that SRC and how this invalidates the 'proof'.

 

I get your 1) and 2). But the conclusion is couched in terms of “every musical transient” and I still cannot see how the generalisation could be “incontrovertible” even if the test could be described as *a* musical transient. My issue is not so much whether it is synthetic but whether it is representative. 

 

It is also worth noting a point you made earlier that the analysis does not include a transient band limited using a minimum phase filter in the src. If it had done so, any pre-ringing from the reconstruction filter could have more clearly been identified. And assuming that the data were properly band limited below nyquist, we could see whether it is indeed necessary to have some pre-ringing following reconstruction. 

[Fokus]

12 hours ago, vl said:

I shall share my own experience.  This is not to indicate the whole world is like my experience.  My DAC is the Auralic Vega.  It has a choice of linear and minimum phase reconstruction filters.  I can hear clarity decrease in upper treble when the minimum phase

 

The Vega's filters all differ in their frequency-magnitude response. That is an observation of JA in the Stereophile review.

 

In order to come to any valid observation as to the audibility of non-linear phase distortion one has to compare two filters that only differ in their frequency-phase response.

 

[vl]

36 minutes ago, Fokus said:

 

The Vega's filters all differ in their frequency-magnitude response. That is an observation of JA in the Stereophile review.

 

In order to come to any valid observation as to the audibility of non-linear phase distortion one has to compare two filters that only differ in their frequency-phase response.

 

 

I was comparing the Vega's mode 1 and mode 4 filters.  The mode 1 filter is linear phase.  The mode 4 filter is minimum phase.  Both filters have similar amplitude responses up to about 18 KHz.  This listening test actually favors this particular minimum phase filter as it is less steep than the linear phase filter.  A minimum phase filter that is equally steep as the linear phase filter will have even more dispersion or phase distortion, leading to more audible smear.  I think Auralic knew what they were doing and did not make the minimum phase filter any steeper.

[esldude]

19 hours ago, mansr said:

I only used the word once.

That just shows how talented you have become since re-imagining yourself in troll form.  You are able to Troll us while only using a word once.  That is high level trolling.  

[Fokus]

2 hours ago, vl said:

 

I was comparing the Vega's mode 1 and mode 4 filters.  ...  Both filters have similar amplitude responses up to about 18 KHz. 

 

Similar is not the same as identical. Moreover, these filters differ significantly in their suppression of images.