John Atkinson: Yes, MQA IS Elegant...

[mansr]

9 minutes ago, Le Concombre Masqué said:

and back to my initial question I simply wanted to know your opinion on CIC, SQ wise ; since you're debating FIR vs IIR, I was simply adding CIC to the discussion

CIC is just an efficient way of implementing a particular class of FIR filters.

[crenca]

9 hours ago, miguelito said:

Drive-by comment: Crossfeed is literally feeding some of the signal from the other channel, with a time lag if done properly, which I imagine the digital crossfeed would do. It is literally an overlay on the time domain so if anything I would think that it would make time smearing comparisons harder.

 

The crossfeed built into Roon (what I use most of the time - have various other plugins for JRiver) implements this "overlay on the time domain" but only in the lower frequencies (user configurable between 300-2000 hz), so no impact in frequencies above this "crossover"...unless I am mistaken which could very well be the case:

 

http://bs2b.sourceforge.net/

[John_Atkinson]

22 hours ago, crenca said:

have we not come to the conclusion that the impulse that JA used to illicit "ringing" in his article is in fact an "illegal" frequency outside of the 20-20 band limit? 

 

As I have said before, spectral analysis shows that the "band-limited impulse" I used has no content above 22.05kHz. However, as I showed in the article, it does have sinc-function ringing present at 22.05kHz.The inference to be drawn is that every musical transient in a CD master will be accompanied by sinc-function ringing at Nyquist, either from the original A/D converter's anti-aliasing filter (if the recording was made at 44.1kHz), or from the sample-rate converter's low-pass filter used to create the master from 2Fs or 4Fs files. It seems incontrovertible, therefore that that ringing will excite the playback DAC's reconstruction filter, which will impose its own ringing on musical transients.

Read more at https://www.stereophile.com/content/zen-art-ad-conversion

 

John Atkinson

Editor, Stereophile

 

[Fokus]

Wrong

[crenca]

31 minutes ago, John_Atkinson said:

 

As I have said before, spectral analysis shows that the "band-limited impulse" I used has no content above 22.05kHz. However, as I showed in the article, it does have sinc-function ringing present at 22.05kHz.The inference to be drawn is that every musical transient in a CD master will be accompanied by sinc-function ringing at Nyquist, either from the original A/D converter's anti-aliasing filter (if the recording was made at 44.1kHz), or from the sample-rate converter's low-pass filter used to create the master from 2Fs or 4Fs files. It seems incontrovertible, therefore that that ringing will excite the playback DAC's reconstruction filter, which will impose its own ringing on musical transients.

Read more at https://www.stereophile.com/content/zen-art-ad-conversion

 

John Atkinson

Editor, Stereophile

 

 

OK, you got me to click on your article.  Along with mansr & fokus and other commentator, I don't see where you actually limited your impulse to "no content above 22.05kHz."  You seem to say the opposite in the article (i.e. you had a 60hz cutoff), but like mansr mentioned the chain you used (i.e. starting with an analogue signal, then converting it to digital, and then seemingly back to digital all before you get to the A/D from Ayer) is confusing...

[mansr]

41 minutes ago, John_Atkinson said:

As I have said before, spectral analysis shows that the "band-limited impulse" I used has no content above 22.05kHz. However, as I showed in the article, it does have sinc-function ringing present at 22.05kHz.The inference to be drawn is that every musical transient in a CD master will be accompanied by sinc-function ringing at Nyquist, either from the original A/D converter's anti-aliasing filter (if the recording was made at 44.1kHz), or from the sample-rate converter's low-pass filter used to create the master from 2Fs or 4Fs files. It seems incontrovertible, therefore that that ringing will excite the playback DAC's reconstruction filter, which will impose its own ringing on musical transients.

A filter "rings" if the input has energy at its cut-off frequency. Everybody knows this. Your experiment confirms it in a roundabout way. For an experiment using an actually band-limited pulse, see my website: https://troll-audio.com/articles/filter-ringing/

[Shadders]

13 minutes ago, mansr said:

A filter "rings" if the input has energy at its cut-off frequency. Everybody knows this. Your experiment confirms it in a roundabout way. For an experiment using an actually band-limited pulse, see my website: https://troll-audio.com/articles/filter-ringing/

Hi,

Can you post as an attachment the band limited pulse ?. (Fig 2).

Can you state the sample rate you used also ?. Thanks.

Regards,

Shadders.

[Miska]

1 hour ago, John_Atkinson said:

As I have said before, spectral analysis shows that the "band-limited impulse" I used has no content above 22.05kHz. However, as I showed in the article, it does have sinc-function ringing present at 22.05kHz.

 

By the way, even if you start with such bandlimited impulse, but play it through a leaky oversampling filter (MQA or Ayre), or a DAC with otherwise imperfect reconstruction, the output will have content beyond 22.05 kHz. In fact most DACs playing 44.1k PCM content will actually have quite a bit of stuff beyond the 22.05 kHz frequency, for example images at multiples of 352.8 kHz digital filter output rate. This needs to be taken into account if the output is to be run to any subsequent ADC.

 

[mansr]

44 minutes ago, Shadders said:

Can you post as an attachment the band limited pulse ?. (Fig 2).

Can you state the sample rate you used also ?. Thanks.

You can create it yourself in Octave/Matlab using "kaiser(49, 35)" and pad with zeros as you see fit. The sample rate doesn't matter. Whatever you decide on, the pulse contains frequencies up to slightly less than fs/4.

[Miska]

Tricky parts are many modern pop/rock recordings that have been recorded with modern ADCs or mastering tools with half-band filters. Where the content systematically reaches exactly Nyquist frequency at high levels (with associated aliasing products in the top frequencies)...

[mansr]

12 minutes ago, Miska said:

Tricky parts are many modern pop/rock recordings that have been recorded with modern ADCs or mastering tools with half-band filters. Where the content systematically reaches exactly Nyquist frequency at high levels (with associated aliasing products in the top frequencies)...

Sure, but nobody is forced to do it that way. If an artist or producer cares to, they can filter the data such that typical reconstruction filters will not ring.

[plissken]

I've never had to google so much as I have in this thread. Thx @mansr , @Miska , @Fokus , @vl , @Archimago.

[Jud]

58 minutes ago, mansr said:

If an artist or producer cares to

 

That of course would be the crux of things.  What proportion care to?

[mansr]

Just now, Jud said:

That of course would be the crux of things.  What proportion care to?

Isn't that the main conceit of MQA, at least as sold to consumers? I'm only pointing out that eliminating ringing of reconstruction filters can be done entirely at the production end. Nobody needs MQA for that.

[vl]

3 hours ago, John_Atkinson said:

 

As I have said before, spectral analysis shows that the "band-limited impulse" I used has no content above 22.05kHz. However, as I showed in the article, it does have sinc-function ringing present at 22.05kHz.The inference to be drawn is that every musical transient in a CD master will be accompanied by sinc-function ringing at Nyquist, either from the original A/D converter's anti-aliasing filter (if the recording was made at 44.1kHz), or from the sample-rate converter's low-pass filter used to create the master from 2Fs or 4Fs files. It seems incontrovertible, therefore that that ringing will excite the playback DAC's reconstruction filter, which will impose its own ringing on musical transients.

Read more at https://www.stereophile.com/content/zen-art-ad-conversion

 

John Atkinson

Editor, Stereophile

 

 

Please help me understand.  

 

In the real world why would a recording engineer or music producer apply an anti aliasing filter that is brick wall steep at the Nyquist frequency?  This is guaranteed to excite the ringing of the anti aliasing filter during the A to D process and the ringing of the reconstruction filter during the D to A process.  Wouldn't the use of a gentler, non brick wall filter to reduce the signal bandwidth to LESS THAN the Nyquist frequency make more sense?  This will avoid excitation of the filters at the Nyquest frequency.

 

Assuming the recording engineer uses a brick wall filter to truncate the bandwidth of the incoming analog music signal at the Nyquist frequency and the music content has energy at the Nyquist frequency, the resulting filter ringing will add its energy to the signal at the Nyquist frequency only, not at other frequencies.  In the case of the CD, does adding a 22.05 KHz ringing to the signal produce an audible effect to the music?

[vl]

1 hour ago, Miska said:

Tricky parts are many modern pop/rock recordings that have been recorded with modern ADCs or mastering tools with half-band filters. Where the content systematically reaches exactly Nyquist frequency at high levels (with associated aliasing products in the top frequencies)...

 

If they are dumb enough to do that, they deserve second rate sound quality.

[vl]

9 minutes ago, mansr said:

Isn't that the main conceit of MQA, at least as sold to consumers? I'm only pointing out that eliminating ringing of reconstruction filters can be done entirely at the production end. Nobody needs MQA for that.

 

I agree.  Even if the ringing is imparted into the recording during the A to D process, we as listeners have choices during playback.

 

1. Leave the ringing there if you believe it is above the audio range of most people therefore not audible.

2. In the playback system apply a moderately steep filter, starting at say 18 KHz, with a healthy attenuation at 22.05 KHz.  That will get rid of the ringing that we cannot hear.

 

I have such a filter in my Direc Live processor, at 17 KHz.  The reason I put it there is so many CDs are badly produced.  They have high distortion in the last octave.  Some CDs, like from Sony Classical, are always clear all the way to the very top end.  This filter does not affect music much but it makes the bad CDs more listenable.

[mansr]

4 minutes ago, vl said:

In the real world why would a recording engineer or music producer apply an anti aliasing filter that is brick wall steep at the Nyquist frequency?

They typically use whatever filter their ADC provides. Here's the step (5 ns rise time) response of a TI PCM4220:

 

4 minutes ago, vl said:

This is guaranteed to excite the ringing of the anti aliasing filter during the A to D process

Any filter with a cut-off below 50 kHz or so will "ring" a little since some musical instruments (mainly percussion) extend that far. If you want no ringing whatsoever, you must record at 176.4 kHz or higher (if we're sticking to the usual rates). At 96 kHz the music can occasionally extend beyond the Nyquist frequency, and thus any filter will necessarily encounter some energy at its cut-off frequency.

 

4 minutes ago, vl said:

and the ringing of the reconstruction filter during the D to A process.  Wouldn't the use of a gentler, non brick wall filter to reduce the signal bandwidth to LESS THAN the Nyquist frequency make more sense?  This will avoid excitation of the filters at the Nyquest frequency.

Did you see my article? Filtering to slightly below Nyquist during production avoids ringing of reconstruction filters entirely.

 

4 minutes ago, vl said:

Assuming the recording engineer uses a brick wall filter to truncate the bandwidth of the incoming analog music signal at the Nyquist frequency and the music content has energy at the Nyquist frequency, the resulting filter ringing will add its energy to the signal at the Nyquist frequency only, not at other frequencies.  In the case of the CD, does adding a 22.05 KHz ringing to the signal produce an audible effect to the music?

A low-pass filter does not add anything to the signal. The "ringing" results when higher frequencies are taken away. It was there all along, just hidden.

[vl]

12 minutes ago, mansr said:

They typically use whatever filter their ADC provides. Here's the step (5 ns rise time) response of a TI PCM4220:

 

Any filter with a cut-off below 50 kHz or so will "ring" a little since some musical instruments (mainly percussion) extend that far. If you want no ringing whatsoever, you must record at 176.4 kHz or higher (if we're sticking to the usual rates). At 96 kHz the music can occasionally extend beyond the Nyquist frequency, and thus any filter will necessarily encounter some energy at its cut-off frequency.

 

Did you see my article? Filtering to slightly below Nyquist during production avoids ringing of reconstruction filters entirely.

 

A low-pass filter does not add anything to the signal. The "ringing" results when higher frequencies are taken away. It was there all along, just hidden.

 

Thanks for the explanation.  I am in agreement with you on all counts.  I should have written - Is the presence of a 22.05 KHz ringing audible in music?

[mansr]

4 minutes ago, vl said:

Thanks for the explanation.  I am in agreement with you on all counts.  I should have written - Is the presence of a 22.05 KHz ringing audible in music?

If you are a cat, sure.

[fas42]

56 minutes ago, vl said:

 

I agree.  Even if the ringing is imparted into the recording during the A to D process, we as listeners have choices during playback.

 

1. Leave the ringing there if you believe it is above the audio range of most people therefore not audible.

2. In the playback system apply a moderately steep filter, starting at say 18 KHz, with a healthy attenuation at 22.05 KHz.  That will get rid of the ringing that we cannot hear.

 

I have such a filter in my Direc Live processor, at 17 KHz.  The reason I put it there is so many CDs are badly produced.  They have high distortion in the last octave.  Some CDs, like from Sony Classical, are always clear all the way to the very top end.  This filter does not affect music much but it makes the bad CDs more listenable.

 

Ummm, this encapsulates where some people have topsy turvy thinking - no CDs are "badly produced" and "have high distortion in the last octave". What some masterings do is emphasis the weaknesses in the playback chain - the problems all exist on the consumer's side, because the manufacturers of the playback gear haven't done enough to reduce the typical digital artifacts, which cause the people listening to decide that they have a "bad CD".

 

It may take much exposure to a well sorted playback rig, easily presenting these 'difficult' recordings in their full glory, for many to understand what's going on, unfortunately.

 

[kumakuma]

19 minutes ago, fas42 said:

 

Ummm, this encapsulates where some people have topsy turvy thinking - no CDs are "badly produced" and "have high distortion in the last octave". What some masterings do is emphasis the weaknesses in the playback chain - the problems all exist on the consumer's side, because the manufacturers of the playback gear haven't done enough to reduce the typical digital artifacts, which cause the people listening to decide that they have a "bad CD".

 

It may take much exposure to a well sorted playback rig, easily presenting these 'difficult' recordings in their full glory, for many to understand what's going on, unfortunately.

 

 

Good god, man. You're like a virus, infecting every thread on this site with your madness.

 

I'm beginning to understand why you've been banned from other forums.

[vl]

3 minutes ago, fas42 said:

 

Ummm, this encapsulates where some people have topsy turvy thinking - no CDs are "badly produced" and "have high distortion in the last octave". What some masterings do is emphasis the weaknesses in the playback chain - the problems all exist on the consumer's side, because the manufacturers of the playback gear haven't done enough to reduce the typical digital artifacts, which cause the people listening to decide that they have a "bad CD".

 

It may take much exposure to a well sorted playback rig, easily presenting these 'difficult' recordings in their full glory, for many to understand what's going on, unfortunately.

 

 

I also agree with what you wrote.  We were making different observations of the same thing.  Some CDs are mastered to sound good on just about any player.  Unfortunately many can sound good only on an excellent playback system.  I want to call the mastering engineers who produce universally good sounding CDs good mastering engineers.

 

Relating to our topics on minimum and linear phase filters, it took me years to arrive at a digital playback system that can play Decca and EMI CDs with good sonic quality.  The magic is in the box that contains the DAC chip but it is not the DAC chip that gives the better sound.  It is the upsampler.  In my case I found a DSP with high computation power using a "long" (steep) linear phase filter is needed to handle the "bad" CDs.

 

 

[fas42]

56 minutes ago, kumakuma said:

 

Good god, man. You're like a virus, infecting every thread on this site with your madness.

 

I'm beginning to understand why you've been banned from other forums.

 

To me, the madness is that everyone blames the recordings - their own playback rig is blemish free, and they use it to sort the "good" from the "bad" ... as in, my car allows me decide which are good, versus bad roads - if the suspension of the vehicle stops me going around a corner at a certain speed, well, it's the civil engineers who got it wrong, they should be punished for their misdemeanours ...

 

I find this idiocy of thinking annoying, and now and again I comment upon it - to redress the balance.

[kumakuma]

24 minutes ago, fas42 said:

 

To me, the madness is that everyone blames the recordings - their own playback rig is blemish free, and they use it to sort the "good" from the "bad" ... as in, my car allows me decide which are good, versus bad roads - if the suspension of the vehicle stops me going around a corner at a certain speed, well, it's the civil engineers who got it wrong, they should be punished for their misdemeanours ...

 

I find this idiocy of thinking annoying, and now and again I comment upon it - to redress the balance.

 

I think you meant to say "again and again, everywhere I possibly can".