MQA is Vaporware

[mansr]

2 minutes ago, esldude said:

So what is audible about MQA?

Only the good parts that can't be explained in standard engineering terms.

[Jud]

1 hour ago, John_Atkinson said:

 

When it comes to recording with slow-rolloff antialiasing filters, as the original sample rate is generally 2Fs or 4Fs, there is no significant top-octave rolloff in the audioband. For example, the "Listen" filter of Ayre's QA-9 A/D converter with a sample rate of 192kHz reaches –3dB at 70kHz but is flat in the top octave (–0.1dB at 20kHz)

 

Thank you for illustrating what I was saying, though I don’t know if you intended to.

 

As you say, in order to avoid significant audible range rolloff, this slow rolloff filter is only down by -3dB 50kHz above the audible range.
 

With such a filter at the recording end, an MQA DAC filter would alias and image, causing intermodulation distortion.

 

In order to avoid ultrasonics that don’t play well with MQA, a slow rolloff filter must cut significantly at the top end of the audible range.

[John_Atkinson]

25 minutes ago, Jud said:

With such a filter at the recording end, an MQA DAC filter would alias and image, causing intermodulation distortion.

 

As I have written, both in this thread and in Stereophile but you must have missed, the probability of there being aliased image energy in the audioband with high-quality recordings of music having a typical spectrum, is very low.  Yes, with music having high amounts of top-octave energy, such as victims of the Loudness Wars that can have an almost-white spectrum, this probability is very much higher. But such recordings sound awful even with steep-rolloff, linear-phase anti-imaging filters.

 

John Atkinson

Technical Editor, Stereophile

 

[crenca]

6 minutes ago, John_Atkinson said:

 

As I have written, both in this thread and in Stereophile but you must have missed, the probability of there being aliased image energy in the audioband with high-quality recordings of music having a typical spectrum, is very low.  Yes, with music having high amounts of top-octave energy, such as victims of the Loudness Wars that can have an almost-white spectrum, this probability is very much higher. But such recordings sound awful even with steep-rolloff, linear-phase anti-imaging filters.

 

John Atkinson

Technical Editor, Stereophile

 

 

If you pay attention to the typical MQA release over at Tidal, you will see that it is indeed the modern compressed lots of top octave energy pop/rap recording.  I suppose if you care for this music, you're glad that it is being recorded with your more typical ADC filter process and being converted to MQA with their hamburger batch processor in the sky, there by avoiding the worst case scenario which Jud is pointing to...😋

 

But this happy accident making up for MQA's inherent faults is just another MQA fail.

 

It's a good thing the audio press applied a little bit of skepticism and criticism and figured all this out before they started promoting it....  🙄

[KeenObserver]

8 hours ago, Tintinabulum said:

And if it was less of a hate fest/campaign, more people would read it. As it is, it's just a dark corner...(waits for click counts data...) 

 

It is a TRUTH fest/campaign.

[kumakuma]

9 hours ago, Tintinabulum said:

And if it was less of a hate fest/campaign, more people would read it. As it is, it's just a dark corner...(waits for click counts data...) 

 

Continuing to play the man, not the ball.

 

 

 

[Samuel T Cogley]

1 hour ago, John_Atkinson said:

 

As I have written, both in this thread and in Stereophile but you must have missed, the probability of there being aliased image energy in the audioband with high-quality recordings of music having a typical spectrum, is very low.  Yes, with music having high amounts of top-octave energy, such as victims of the Loudness Wars that can have an almost-white spectrum, this probability is very much higher. But such recordings sound awful even with steep-rolloff, linear-phase anti-imaging filters.

 

The majority of MQA-encoded material is indeed "victims of the Loudness Wars".  I think this is a tacit acknowledgement that MQA makes horrible sounding material sound worse.

[John_Atkinson]

3 hours ago, mansr said:

If you look at your own graphs, you'll see that even the Ayre "listen" filter reaches about 90 dB attenuation at 40 kHz and stays there. In contrast, the MQA filters achieve at best 40 dB attenuation apart from a few narrow dips. Like this:

 

 I am note sure what filter that is, other than a simple moving-average type.  If you look at fig.2 in my measurements of the Mytek Liberty DAC (below) - which uses one of the MQA filters for all PCM data - see https://www.stereophile.com/content/mytek-liberty-da-processor-measurements - the filter has a slow rolloff off above the audioband, with very little suppression of the image at 25kHz of a 19.1kHz tone. However, there are no aliased images of this high-level tone in the audioband and the stop-band attenuation is consistent with frequency..

 

John Atkinson

Technical Editor, Stereophile

 

[Rt66indierock]

9 hours ago, Tintinabulum said:

And if it was less of a hate fest/campaign, more people would read it. As it is, it's just a dark corner...(waits for click counts data...) 

 

How often have I said lets spread a little more darkness. We are the ones putting MQA in a dark corner. 

[Jud]

1 hour ago, John_Atkinson said:

 

As I have written, both in this thread and in Stereophile but you must have missed, the probability of there being aliased image energy in the audioband with high-quality recordings of music having a typical spectrum, is very low.  Yes, with music having high amounts of top-octave energy, such as victims of the Loudness Wars that can have an almost-white spectrum, this probability is very much higher. But such recordings sound awful even with steep-rolloff, linear-phase anti-imaging filters.

 

John Atkinson

Technical Editor, Stereophile

 

I didn’t say the distortion would necessarily be at audible levels. But as I mentioned a couple of comments ago, “This bad filter produces distortion, but likely not enough to hear most of the time” doesn’t exactly put one in mind of “Master Quality.” Also note as I mentioned previously that for the very same reason MQA cannot ‘deblur’ anything (remove Gibbs effect frequency from an original that has it), and that was the main selling point, was it not?

[Rt66indierock]

2 hours ago, John_Atkinson said:

 

As I have written, both in this thread and in Stereophile but you must have missed, the probability of there being aliased image energy in the audioband with high-quality recordings of music having a typical spectrum, is very low.  Yes, with music having high amounts of top-octave energy, such as victims of the Loudness Wars that can have an almost-white spectrum, this probability is very much higher. But such recordings sound awful even with steep-rolloff, linear-phase anti-imaging filters.

 

John Atkinson

Technical Editor, Stereophile

 

 

John, I just got back from a concert in Texas. Dr Dog and Shakey Graves put out a lot top-octave energy live Saturday night.

 

Little hand says its time to rock and roll.

[Doug Schneider]

2 hours ago, John_Atkinson said:

 

Fairly wide bandwidth? Not really, Yes, if you are talking about the level of a tweeter, I have found, in a blind test, that I can detect a level difference of just 0.5dB. But that 0.5dB difference covered 2.5kHz-20kHz, ie, 3 octaves, which is a large "area under the curve." In the case of the example of the slow-rolloff reconstruction filter I gave,  the output is flat to 10kHz, -0.1dB at 13kHz, -0.86dB at 17kHz, and -2.4dB at 20kHz, ie, the area under the curve is very small. And that area is in a region where human hearing sensitivity is reduced compared with frequencies below 13kHz. I doubt that it will be audible.

 

Not at all what I've found -- and what many designers I've talked to have found. We're not talking about starting so low in frequency, we're talking about the top octave of the audioband, so 10kHz upwards, which is precisely what you're talking about with these digital filters. As you know, I "talk shop" with a number of the world's top speaker designers and the difference of even 0.5dB in that top range can be significant enough to turn a speaker from "a little too bright" to "just right." In the case of one very famous and well-selling top-end loudspeaker, that's exactly the difference that was made in the final voicing. A 3dB difference in that top octave can be profound. So while you may doubt it, I don't doubt that it can be clearly audible.

 

Doug Schneider

SoundStage!

[marce]

Hmmm, maybe instead of MQA, going back to  bass and treble controls might be easier...😀

 

[mfsoa]

Oh boy have you guys (anti-MQA) tossed a softball to MQA/Stereophile/TAS that they surely can't resist taking a swing at...

 

Imagine the boost to MQA's credibility - Imagine how important it would be for SPhile and TAS to be vindicated as the technical and industry leaders who boldly and accurately proclaimed the second coming of sliced bread - Imagine how embarrassed all the nattering nabobs of MQA negativity would be - Imagine (if this is anyone's desire) the (small) harm to this website and the credibility of it's founder. Just imagine how the MQA critics would be silenced once and for all, and how it would clear the path for broad acceptance of this wonderful new standard...

 

All MQA/SPhile/TAS has to do is simply answer the few technical questions posed here, with verifiable results.

 

Seems pretty straightforward to me, given the awesome power of MQA to do these incredible things to sound quality that have eluded all other digital designers to date.

 

Or, maybe not...

 

The silence is deafening.

 

 

(BTW, my brother owns a brick 'n mortar stereo shop. Yep, right next to the buggy whip factory. Very few customers know about MQA but there are definitely some who have bought into the "Without MQA this device will be obsolete in a year..." thing. Why would trade magazines be pushing to make all current digital audio hardware obsolete? Hmmm...)

 

[Thuaveta]

16 minutes ago, marce said:

Hmmm, maybe instead of MQA, going back to  bass and treble controls might be easier...😀

 

 

[mansr]

16 minutes ago, John_Atkinson said:

I am note sure what filter that is, other than a simple moving-average type.

Clearly (to any EE undergrad student), it is not a simple moving average. It is one of the MQA 8x upsampling filters extracted from a Dragonfly DAC.

 

16 minutes ago, John_Atkinson said:

If you look at fig.2 in my measurements of the Mytek Liberty DAC (below) - which uses one of the MQA filters for all PCM data - see https://www.stereophile.com/content/mytek-liberty-da-processor-measurements - the filter has a slow rolloff off above the audioband, with very little suppression of the image at 25kHz of a 19.1kHz tone.

That's not one of the normal MQA filters. Your plot ends at 100 kHz, and noise sets in around -125 dB, so it's hard to tell what the true frequency response looks like. The impulse response plot in the article is too squashed to be of much use. It does, however, show that the sign is flipped, something I have never seen MQA do. The straight slope in the transition band is also unheard of in MQA filters.

 

As you mention in the article, the attenuation of the 25 kHz image is less than 20 dB. Looking at the higher frequency images, we find the one at 63.2 kHz attenuated by ~100 dB and the one at 69 kHz by a little less than 90 dB. There is clearly considerable variation in the stop band, as is also hinted at by the wavy "floor" in the graph.

 

The "generic" MQA filter used for content with an original sample rate of 96 kHz or lower looks like this:

 

16 minutes ago, John_Atkinson said:

However, there are no aliased images of this high-level tone in the audioband and the stop-band attenuation is consistent with frequency..

Once again, your ignorance of how aliasing/imaging works is betrayed.

[The Computer Audiophile]

1 hour ago, mfsoa said:

All MQA/SPhile/TAS has to do is simply answer the few technical questions posed here, with verifiable results.

I've asked the MQA team for such information. I said I would happily publish anything that proves anyone wrong because I want the correct info. I offered to publish anything from anyone who can show MQA is correct in its assertions and the people here are wrong.

 

So far, nobody has taken me up. Makes me wonder. 

[Doug Schneider]

22 minutes ago, The Computer Audiophile said:

I've asked the MQA team for such information. I said I would happily publish anything that proves anyone wrong because I want the correct info. I offered to publish anything from anyone who can show MQA is correct in its assertions and the people here are wrong.

 

So far, nobody has taken me up. Makes me wonder. 

 

I would say who said this, but I didn't ask his permission, so I won't name him out loud. But when I told a top digital designer I couldn't get any technical details from the company to truly prove their claims, he replied with, "That right there should tell you what you need to know."

 

This whole deblurring thing, if true, could've been so easily proved. Get an ADC that's the supposed culprit. Record something that's "blurry." Then "unblur" it. Prove to everyone you can. Case closed. But no........... instead, let some audio writers tell the world it can and have them dig their heels further and further into the ground when asked.

 

I come from a technical background in IT -- any time someone came with some claim, the first thing you did was ask them to prove it. If they were real, they did.

 

Doug Schneider

SoundStage!

[Ralf11]

3 hours ago, John_Atkinson said:

 

As I have written, both in this thread and in Stereophile but you must have missed, the probability of there being aliased image energy in the audioband with high-quality recordings of music having a typical spectrum, is very low.  ...

 

John Atkinson

Technical Editor, Stereophile

 

 

 

Would you please post the data for the probabilities?

 

If you have it broken down by musical genres that would be even better.

[crenca]

2 hours ago, John_Atkinson said:

 

 I am note sure what filter that is, other than a simple moving-average type.  If you look at fig.2 in my measurements of the Mytek Liberty DAC (below) - which uses one of the MQA filters for all PCM data - see https://www.stereophile.com/content/mytek-liberty-da-processor-measurements - the filter has a slow rolloff off above the audioband, with very little suppression of the image at 25kHz of a 19.1kHz tone. However, there are no aliased images of this high-level tone in the audioband and the stop-band attenuation is consistent with frequency..

 

John Atkinson

Technical Editor, Stereophile

 

 

Before I scrolled down to @mansrpost JA I saw this and said "this is not an MQA filter".

 

An error has been made...

 

edit:  what's the date of this measurement?  was it when this DAC first came out?  was there not an firmware update that "fixed" several issues with this DAC early in its lifecycle (going from memory here)?  If this is in fact how its measured during this early period with MQA material (properly selected), I am wondering if one of things that was "fixed" and/or updated was its MQA filters...

[rickca]

5 minutes ago, Doug Schneider said:

"That right there should tell you what you need to know."

MQA's claims about delivering the sound of the studio and raves from opinion influencers about the birth of a new world cannot survive without a cloak of mystery and NDA's.  I don't expect any clarification of technical details from MQA, just more technobabble.  As long as MQA can achieve their business development goals without responding to challenges posed here, they aren't likely to welcome further scrutiny.

[botrytis]

27 minutes ago, Doug Schneider said:

 

I would say who said this, but I didn't ask his permission, so I won't name him out loud. But when I told a top digital designer I couldn't get any technical details from the company to truly prove their claims, he replied with, "That right there should tell you what you need to know."

 

This whole deblurring thing, if true, could've been so easily proved. Get an ADC that's the supposed culprit. Record something that's "blurry." Then "unblur" it. Prove to everyone you can. Case closed. But no........... instead, let some audio writers tell the world it can and have them dig their heels further and further into the ground when asked.

 

I come from a technical background in IT -- any time someone came with some claim, the first thing you did was ask them to prove it. If they were real, they did.

 

Doug Schneider

SoundStage!

 

This is one of the big issues. MQA hasn't proven anything about it. All they say, you know *WINK WINK* and that is it. It causes me to pause.

[marce]

1 hour ago, Thuaveta said:

 

No but you can tank up the treble and drive teenagers from your listening room.

[esldude]

1 hour ago, mansr said:

Clearly (to any EE undergrad student), it is not a simple moving average. It is one of the MQA 8x upsampling filters extracted from a Dragonfly DAC.

 

That's not one of the normal MQA filters. Your plot ends at 100 kHz, and noise sets in around -125 dB, so it's hard to tell what the true frequency response looks like. The impulse response plot in the article is too squashed to be of much use. It does, however, show that the sign is flipped, something I have never seen MQA do. The straight slope in the transition band is also unheard of in MQA filters.

 

As you mention in the article, the attenuation of the 25 kHz image is less than 20 dB. Looking at the higher frequency images, we find the one at 63.2 kHz attenuated by ~100 dB and the one at 69 kHz by a little less than 90 dB. There is clearly considerable variation in the stop band, as is also hinted at by the wavy "floor" in the graph.

 

The "generic" MQA filter used for content with an original sample rate of 96 kHz or lower looks like this:

 

Once again, your ignorance of how aliasing/imaging works is betrayed.

Come on mansr, just because his digitally created test tones had no DAC aliasing?

[kumakuma]

2 minutes ago, marce said:

No but you can tank up the treble and drive teenagers from your listening room.

 

Or get one of these:

 

http://argoasecurity.com/index.php?route=product/product&product_id=21