MQA is Vaporware

[mansr]

3 minutes ago, John_Atkinson said:

I downloaded the file - thank you, mansr - but Roon doesn't recognize it as MQA-encoded. As it is a 24/96 FLAC file, I wondered if it is the rendered version for which mansr posted the spectrum. However, a file sampled at 96kHz can't have content at 80kHz.

The file should be played on a DAC with MQA rendering ability, such as an iFi or a Dragonfly, to which it looks like the output from an MQA "core" decoder.

[mansr]

39 minutes ago, manisandher said:

You can fool the MQA renderer into thinking that this is an MQA-encoded signal that has been decoded?

Exactly. Software here: https://code.videolan.org/mansr/mqa

[manisandher]

9 minutes ago, John_Atkinson said:

However, a file sampled at 96kHz can't have content at 80kHz.

 

No, the renderer seems to be adding the 80kHz content.

[John_Atkinson]

31 minutes ago, mansr said:

The file should be played on a DAC with MQA rendering ability, such as an iFi or a Dragonfly, to which it looks like the output from an MQA "core" decoder.

 

Right. Subsequent to my posting, I realized that your file was intended to be the first "unfold," not an undecoded MQA file, and that you were looking just at what the renderer did. I therefore used Roon to send the data to a PS Audio DirectStream DAC set to be the renderer only. Will get back to you with what I find.

 

John Atkinson

Technical Editor, Stereophile

[John_Atkinson]

55 minutes ago, John_Atkinson said:

I therefore used Roon to send the data to a PS Audio DirectStream DAC set to be the renderer only. Will get back to you with what I find.

 

I have attached two graphs, both taken with the full-scale 10kHz tone. The analyzer was set to a  200kHz sample rate, so should reveal the spuriae mansr found. As you can see, while there are some low-level enharmonic spuriae in the spectrum, there is nothing present at 80kHz. The sinewave is clean, without the 80kHz overlay that mansr found. So either mansr's measurements were picking up interference - though the integer relationship between the encoded tone and the spuriae suggests not - or the PS Audio DAC as a renderer was not recognizing the data as MQA-encoded. (It does do so with MQA music files.)

 

John Atkinson

Technical Editor, Stereophile

[The Computer Audiophile]

25 minutes ago, John_Atkinson said:

or the PS Audio DAC as a renderer was not recognizing the data as MQA-encoded

Does the MQA light illuminate?

[mansr]

5 minutes ago, John_Atkinson said:

I have attached two graphs, both taken with the full-scale 10kHz tone. The analyzer was set to a  200kHz sample rate, so should reveal the spuriae mansr found. As you can see, while there are some low-level enharmonic spuriae in the spectrum, there is nothing present at 80kHz. The sinewave is clean, without the 80kHz overlay that mansr found.

The anomaly is at 86 kHz.

 

5 minutes ago, John_Atkinson said:

So either mansr's measurements were picking up interference

Then it wouldn't have scaled with the signal down to -60 dB.

 

5 minutes ago, John_Atkinson said:

- though the integer relationship between the encoded tone and the spuriae suggests not - or the PS Audio DAC as a renderer was not recognizing the data as MQA-encoded. (It does do so with MQA music files.)

 

John Atkinson

Technical Editor, Stereophile

I see a distinct spike at what could be 86 kHz there. It is much lower in level than what I'm getting from my DAC though.

 

5 minutes ago, John_Atkinson said:

What is that figure showing?

[John_Atkinson]

3 minutes ago, mansr said:

Quote

Read more  

What is that figure showing?

 

The PS Audio's analog output waveform while it decodes your 10kHz, 0dBFS tone. The spectrum I posted is the frequency-domain analysis of this waveform, though over a much longer time window, of course.

 

John Atkinson

Technical Editor, Stereophile

 

 

[mansr]

Here's the spectrum (normalised so the peak hits 0 dB) of a software "render" of that signal:

The 86 kHz artefact is supposed to be there at -24 dB. Could it be that PS Audio DAC has a low-pass filter somewhere after the MQA rendering?

[John_Atkinson]

1 minute ago, mansr said:

Could it be that PS Audio DAC has a low-pass filter somewhere after the MQA rendering?

 

I don't think so. I will repeat the test with a Mytek Brooklyn DAC and see if  get a different result.

 

John Atkinson

Editor, Stereophile

 

[The Computer Audiophile]

You nerds. 

[Miska]

4 minutes ago, mansr said:

The 86 kHz artefact is supposed to be there at -24 dB. Could it be that PS Audio DAC has a low-pass filter somewhere after the MQA rendering?

 

Hard to say how much, but at least this unit has at leat -10 dB or more by 86 kHz:

https://www.stereophile.com/content/ps-audio-perfectwave-directstream-da-processor-measurements

 

[Miska]

I can also do some measurements for example with Pro-Ject Pre Box S2 Digital when I get back home...

 

[The Computer Audiophile]

Nerdfest continues. I love it. 

[John_Atkinson]

48 minutes ago, John_Atkinson said:

I will repeat the test with a Mytek Brooklyn DAC and see if  get a different result.

 

 Okay, I got different results with the Mytek Brooklyn. The front panel indicated that the 24/96 FLAC file was being rendered as 24/192k and a red rather than blue light illuminated next to the MQA indicator. This time, the spectrum with the 10kHz at 0dBFS was dirty, with an 86kHz component at -30dB. The waveform, however, was still visually clean.

 

John Atkinson

Technical Editor, Stereophile

[asdf1000]

https://www.billboard.com/articles/business/8526675/apple-music-launches-apple-digital-masters

 

From what I gather, for now, "Digital Masters" is just 'Mastered for iTunes' moving to Apple Music...

 

[jmsent]

9 minutes ago, Em2016 said:

https://www.billboard.com/articles/business/8526675/apple-music-launches-apple-digital-masters

 

 

https://www.theverge.com/2019/8/7/20758633/apple-digital-masters-itunes-rebrand-music-quality.  

 

This article states that Apple is still sticking with 256kbs for streaming quality...so "Apple digital masters" applies strictly to the mastering side for now.

[asdf1000]

Just now, jmsent said:

This article states that Apple is still sticking with 256kbs for streaming quality...so "apple digital masters" applies strictly to the mastering side for now.

 

Yes, said the same above. For now, "Digital Masters" is just 'Mastered for iTunes' moving to Apple Music...

[asdf1000]

Deleted, double

[psjug]

5 hours ago, mansr said:

High or low level makes no difference. The relative amount of imaging (aliasing is something else) is the same regardless.

So this all has to do with MQA creating the stuff above 48KHz entirely from images of the real material, correct?  Are you able to characterize the magnitude of the imaging as a function of frequency?

[Rt66indierock]

8 minutes ago, Em2016 said:

https://www.billboard.com/articles/business/8526675/apple-music-launches-apple-digital-masters

 

Notice how cryptic everyone is about what is actually mastered for iTunes. And from the Verge no evidence that Tidal has made enough waves to bother. 

[asdf1000]

2 minutes ago, Rt66indierock said:

 

Notice how cryptic everyone is about what is actually mastered for iTunes. And from the Verge no evidence that Tidal has made enough waves to bother. 

 

It's not cryptic for now. It's the lossy 'Mastered for iTunes' moving to Apple Music, for now.

 

But The Verge asks "Is this Apple’s stepping stone to lossless streaming?"

 

and then finishes with

 

"But here’s to hoping, especially when even Amazon is now thinking about going down this road. "

[Rt66indierock]

1 minute ago, Em2016 said:

 

It's not cryptic for now. It's the lossy 'Mastered for iTunes' moving to Apple Music, for now.

 

But The Verge asks "Is this Apple’s stepping stone to lossless streaming?"

 

and then finishes with

 

"But here’s to hoping, especially when even Amazon is now thinking about going down this road. "

 

The majors haven't given them a lot of hi-res. So keep hoping.

[Ishmael Slapowitz]

4 minutes ago, Em2016 said:

 

It's not cryptic for now. It's the lossy 'Mastered for iTunes' moving to Apple Music, for now.

 

But The Verge asks "Is this Apple’s stepping stone to lossless streaming?"

 

and then finishes with

 

"But here’s to hoping, especially when even Amazon is now thinking about going down this road. "

The article is misleading on so many levels.

 

First, they are trying a sleight of of hand to make those with only casual knowledge of digital audio think

that lossy encodes from 24 bit master files are somehow high resolution.

 

Second, Mastered For iTunes is nothing but utter marketing pablum. Encoding to AAC from the master files...they think

'this is a special favor they are doing? What else would you encode from.

 

Apple has been a major enemy of moving the quality fo recorded music forward since 2001.

[asdf1000]

2 minutes ago, Rt66indierock said:

 

The majors haven't given them a lot of hi-res. So keep hoping.

 

We shall see. If Amazon makes the real first move, all theories discussed on the golf course with golfing buddies go out the window....

 

In the context of MQA, this is a good thing. If MQA can get pushed out the way.