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MQA is Vaporware


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35 minutes ago, John_Atkinson said:

The latter has a much cleaner spectrum, though the aliased product at 86kHz lies close to the same level.

 

I know @mansr has already pointed this out, but you really should refer to this as 'imaging' and not 'aliasing'.

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12 minutes ago, manisandher said:

 

I know @mansr has already pointed this out, but you really should refer to this as 'imaging' and not 'aliasing'.

 

Imaging is a brain phenomenon, not a file issue.

 

I am not aware of how one can measure imaging in a file since your ears and brain determine that.

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1 hour ago, John_Atkinson said:

Here are both the spectrum of the Mytek Brooklyn's analog output rendering mansr's original file, 10kHz at 0dBFS, which he says may have had some clipping (or inter-sample overs), and his new file, 10kHz at -3dBFS. The latter has a much cleaner spectrum, though the aliased product at 86kHz lies close to the same level.

 

John Atkinson

Technical Editor, Stereophile

Mansr 10k-3dB Mytek Spectrum.jpg

There are a few things happening here. First we have the 10 kHz tone that's actually in the file. Then we have the 86 kHz image created by the MQA filter. At 20 kHz and 30 kHz we have harmonics (distortion) of the 10 kHz tone. The spikes at 66 kHz, 76 kHz, and 96 kHz are the result of intermodulation between the 10 kHz and 86 kHz frequencies. No idea what's going on at 94 kHz. Anyone care to speculate?

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1 hour ago, mansr said:

I'm somewhat surprised by the reactions. There is nothing here that hasn't been known for years.

 

There is knowledge (facts, truth) and then there is knowledge (culture).  Look at that that comment by Brian Lucey @Ishmael Slapowitzposted - it's the formal talking to the latter (i.e. Jim Austin, Stereophile and the industry insider "let's give MQA yet another benefit of the doubt" writeup).

Hey MQA, if it is not all $voodoo$, show us the math!

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2 hours ago, firedog said:

Okay, are we agreed now that the MQA renderer/filters distorts the waveform?


At least it's good to see that those who first questioned the need for peer review, now are part of peer reviewing @mansr test signals.

I call this progress. I consider the second unfold a modified upsampler, which clearly distorts the waveform. Some time ago we played with @Archimago's goldilocks filter and since then I could even care less about MQA's weird upsampling filter.

A very similar recipe as MQA's minimum phase leaky upsampler with one cycle of post-ringing can be found in my signature. I do not like this filter.
 

Designer of the 432 EVO music server and Linux specialist

Discoverer of the independent open source sox based mqa playback method with optional one cycle postringing.

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20 minutes ago, psjug said:

For me, presenting it this way where we see what the leaky filters do to a simple waveform drives it home a little more.  It looks a lot like a filterless DAC.

 

That is the philosophy that Bob S/MQA Ltd. is presenting as both something new and true.  Yet, a "filterless DAC" is old and "an opinion" (depending upon what you believe about "ringing", preference of phase, etc.).  Not that the "Audio Press" has explained this to you...

 

20 minutes ago, psjug said:

 

Also, I guess we can take away from this that if we are force-fed MQA it is better to just do the first unfold and ditch the renderer?

 

Yes - though I still have questions about the relative pros and cons when compared to just playing MQA as a pseudo 24/48 file (i.e. not unfolding/decoding it) in a force-fed MQA world.

Hey MQA, if it is not all $voodoo$, show us the math!

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