MQA is Vaporware

[mansr]

3 minutes ago, John_Atkinson said:

Okay. Ignoring your nasty little insults, what was the frequency and the level of the sinewave?

If you can't figure that out, why should we listen to a single word you say?

[mansr]

1 hour ago, Paul R said:

This is is a bit disingenuous

If by "this" you are referring to MQA, then I agree.

[The Computer Audiophile]

22 minutes ago, mansr said:

If you can't figure that out, why should we listen to a single word you say?

People less skilled in this area can't figure it out either. Please help them, even if it hurts you to simultaneously help John :~)

[manisandher]

9 minutes ago, mansr said:

If you can't figure that out, why should we listen to a single word you say?

 

Why not just answer his question, and then perhaps outline how the answer could have been arrived at from the scope shot itself?

[crenca]

3 hours ago, mansr said:

Getting back on topic, here's a scope capture showing the "improved" time domain performance of MQA. It's supposed to be a sine wave. A child with a crayon could do a better rendering.

 

 

I'm confused as well.  I thought there were no test signals of any kind encoded with MQA - only music.  Did you use a piece of MQA electronica? Looks like a NOS...

[mansr]

The exact frequency isn't important. The point is that it looks only vaguely like a sine wave.

[mansr]

Just now, crenca said:

I'm confused as well.  I thought there were no test signals of any kind encoded with MQA - only music.  Did you use a piece of MQA electronica? Looks like a NOS...

We can create test signals for input to an MQA "renderer" which is what this is. If the decoded MQA file contained a pure sine wave, this is what a renderer would produce.

[John_Atkinson]

1 hour ago, mansr said:

1 hour ago, John_Atkinson said:

Okay. Ignoring your nasty little insults, what was the frequency and the level of the sinewave?

If you can't figure that out, why should we listen to a single word you say?

 

Both when I was studying for my post-graduate qualification as a high-school science teacher and later when I took a management training course on how best to treat subordinates, I was taught that "There are no stupid questions, just stupid answers."

 

Your answers to my questions nicely illustrate that maxim. 🙂

 

John Atkinson

Technical Editor, Stereophile

 

[mansr]

Are you still insisting that you don't know how to read a standard oscilloscope display?

[psjug]

8 minutes ago, John_Atkinson said:

 

Both when I was studying for my post-graduate qualification as a high-school science teacher and later when I took a management training course on how best to treat subordinates, I was taught that "There are no stupid questions, just stupid answers."

 

Your answers to my questions nicely illustrate that maxim. 🙂

 

John Atkinson

Technical Editor, Stereophile

 

Not all instructors feel this way.  I remember a professor who often responded to questions with "Now why don't you know that?"

[christopher3393]

16 minutes ago, psjug said:

Not all instructors feel this way.  I remember a professor who often responded to questions with "Now why don't you know that?"

 

Lame excuse.  🙄

[John_Atkinson]

15 minutes ago, psjug said:

I remember a professor who often responded to questions with "Now why don't you know that?"

 

The answer to his question should have been "Because you haven't explained it."

 

Or perhaps, as in the case of Mansr's recent posts, it is because he doesn't  actually understand it 🙂

 

If the sinewave is close to the Nyquist Frequency and high in level, the scope trace is showing aliasing with a low-rolloff reconstruction filter. Nothing unusual about that and not restricted to MQA. If it is a low-frequency, low-frequency sinewave well below Nyquist, then I have no idea what is generating the additional tone. I haven't seen anything like that in my own measurements.

 

John Atkinson

Technical Editor, Stereophile

[kumakuma]

29 minutes ago, John_Atkinson said:

 

I was taught that "There are no stupid questions, just stupid answers."

 

 

I used to say this to students all the time to reassure them they could ask anything they want.

 

The nice thing about this expression is that also applies when you are asking them questions.

[mansr]

The thing is, I'm sure JA knows how to read a scope, just as I'm sure he's pretending otherwise in order to distract attention from the real issue.

[mansr]

7 minutes ago, John_Atkinson said:

If the sinewave is close to the Nyquist Frequency and high in level, the scope trace is showing aliasing with a low-rolloff reconstruction filter.

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

[mansr]

9 minutes ago, John_Atkinson said:

I haven't seen anything like that in my own measurements.

How would you know, if you can't even read a scope display?

[John_Atkinson]

3 minutes ago, mansr said:

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

 

Actually no (and ignoring your continuing gratuitous insults). If the signal is low in level, the aliased images may well lie below the noisefloor.

 

John Atkinson

Technical Editor, Stereophile

 

[psjug]

34 minutes ago, John_Atkinson said:

 

The answer to his question should have been "Because you haven't explained it."

 

I'm sure you realize that this reply would not have helped.  On your question about frequency, I would have just counted the divisions on the display once it became clear that mansr was not going to give you the answer.

[mansr]

Here's another scope image. The yellow trace (left channel) is unchanged. The blue trace (right channel) is the same sine wave at -60 dBFS. There's some high-frequency (750 kHz) noise riding on it, but the same distortion is clearly recognisable.

 

The frequency of the sine wave is 10 kHz. Sample rate is 96 kHz.

 

 

Same signal, same DAC without MQA rendering:

[John_Atkinson]

5 minutes ago, mansr said:

Here's another scope image. The yellow trace (left channel) is unchanged. The blue trace (right channel) is the same sine wave at -60 dBFS. There's some high-frequency (750 kHz) noise riding on it, but the same distortion is clearly recognisable.

 

The frequency of the sine wave is 10 kHz. Sample rate is 96 kHz.

 

Thank you. This is intriguing. The content added by the renderer appears to have a frequency of 80kHz and as you say, is not affected by signal level. It therefore can't be due to aliasing.

 

John Atkinson

Technical Editor, Stereophile

[mansr]

Here's the file, in case someone wants to test for themselves.

sine-10k-0db-60db-mqb.flac

[manisandher]

2 hours ago, mansr said:

We can create test signals for input to an MQA "renderer" which is what this is.

 

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

[Paul R]

3 hours ago, tmtomh said:

 

if you are "not sure what [he is] trying to show here and have no intention of guessing," then logically you have no basis upon which to claim that @mansr's graph is "a bit disingenuous."

 

Being not sure and being ignorant are two different things, and conflating them is also disingenuous.  

[Ralf11]

1 hour ago, psjug said:

Not all instructors feel this way.  I remember a professor who often responded to questions with "Now why don't you know that?"

 

but he said "high school science teacher" not a university professor

 

for the record, as an undergrad. we used to get "That's intuitively obvious" as a response to questions in college physics classes.  

[John_Atkinson]

49 minutes ago, manisandher said:

2 hours ago, mansr said:

We can create test signals for input to an MQA "renderer" which is what this is.

 

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

 

I downloaded the file - thank you, mansr - but Roon doesn't recognize it as MQA-encoded.

 

John Atkinson

Technical Editor, Stereophile