MQA technical analysis

[mansr]

Go away, witchdoctor. You are not welcome in this thread.

[witchdoctor]

9 minutes ago, mansr said:

Go away, witchdoctor. You are not welcome in this thread.

This site has a feature called ignore, it works. I have you set to ignore and never see what you post unless I choose to. I suggest you do the same with me.

[mansr]

27 minutes ago, witchdoctor said:

This site has a feature called ignore, it works. I have you set to ignore and never see what you post unless I choose to. I suggest you do the same with me.

Please do not post again in this thread, regardless of who is on your ignore list. You only noticed the thread because I posted something, and you immediately dug out an old post from July, which was already tangential to the topic, to which you could attach your drivel. You clearly did this for no other reason than to disrupt the conversation.

 

Go away, and don't come back.

 

@The Computer Audiophile, please make sure he stays away.

[firedog]

What certain people keep "forgetting" is that we have already established that different DACs certified for MQA are being sold with the same filters. Ergo, MQA is lying about using "DAC specific" filters to reduce smearing on the DAC end. 

[Shadders]

1 hour ago, witchdoctor said:

You hit the nail on the head, they are trying to deliver the sound of the studio.

 

The suitable playback system is a HUGE part of the chain. I think you can replicate the sound in the studio without a lot of effort or budget. 

Hi,

With regards to the delivery of the sound of the studio - this is impossible, as the studio uses lossless encoding, MQA is lossy with distortion (aliasing) - certainly not studio sound.

 

With regards to the suitable playback - see link below and copied text referring :

 

http://www.theabsolutesound.com/articles/beyond-high-resolution/?page=3

 

"As Fig. 3 shows, temporal blur is cumulative; each successive stage can inadvertently spread transient energy over a wider and wider interval. It’s not uncommon for a signal to have been subjected to a cascade of eight filters by the time it’s gone from microphone to loudspeaker; the damage is significant, and yet each individual stage isn’t that bad in isolation."

 

Therefore, you do not need to compensate for the DAC - and in fact MQA does NOT compensate for the DAC - as they all use the same filters.

 

So, from a technical approach, MQA statements are not accurate. It neither delivers studio sound, nor does it require a DAC specific filter, which implies it does not need to be part of the DAC design process, collecting royalties from each unit sold ?

 

Regards,

Shadders.

[witchdoctor]

10 minutes ago, Shadders said:

 

 

So, from a technical approach, MQA statements are not accurate. It neither delivers studio sound, nor does it require a DAC specific filter,

From page 3 in the article you posted:

"In fact, the signal heard in the studio is delivered and authenticated with lossless bit-for-bit precision to the listener."

 

 

[FredericV]

7 minutes ago, Shadders said:

Hi,

With regards to the delivery of the sound of the studio - this is impossible, as the studio uses lossless encoding, MQA is lossy with distortion (aliasing) - certainly not studio sound.

Indeed almost impossible and not for the typical audiophile MQA is trying to lure into their DRM ecosystem. Here's an approximation with monitors which are also in grammy award winning studio's, the difference between nearfield and farfield is quite dramatic:

 

I did all our shootouts related to claims about studio formats in nearfield. All mistakes in MQA were revealed very easily.

[mansr]

15 minutes ago, firedog said:

What certain people keep "forgetting" is that we have already established that different DACs certified for MQA are being sold with the same filters. Ergo, MQA is lying about using "DAC specific" filters to reduce smearing on the DAC end. 

Well, we've only been able to obtain the actual filter coefficients stored in the firmware from the Bluesound. Now the measured impulse response from the other devices is a very close match to these coefficients. The DAC compensation would presumably make the output of different DACs look the same, and the measurements do agree. Where it falls apart is that these measured outputs so closely match the input on the Bluesound. This means that either a) the Bluesound DAC is completely transparent while the others still require compensation, or b) all DACs are virtually transparent and actually use the same filters. I find alternative b far more likely.

[mansr]

witchdoctor, I told you to go away, yet you are still here. @The Computer Audiophile, could you please help our friend understand my request?

[Shadders]

21 minutes ago, witchdoctor said:

From page 3 in the article you posted:

"In fact, the signal heard in the studio is delivered and authenticated with lossless bit-for-bit precision to the listener."

 

Hi,

If the system was not lossy, but is lossless, then the answers as per Bob Stuart must be called into question :

 

See answers A.55, A.81.

 

Also, please see :

https://benchmarkmedia.com/blogs/application_notes/163302855-is-mqa-doa

Figure 7A which shows the lossy encoding - from the MQA patent.

 

As such, how can it be bit-for-bit precision ?

 

Please provide the technical answer, given that this is a technical thread.

Thanks and regards,

Shadders.

 

[mansr]

Everybody, please stop responding to witchdoctor. He has his own thread where he's free to blather as much as he wants.

[The Computer Audiophile]

@witchdoctor No more posts in this thread. Your doing your best to derail any MQA discussions that don't mind with your agenda. One more time and you're banned. 

[Ralf11]

7 hours ago, firedog said:

What certain people keep "forgetting" is that we have already established that different DACs certified for MQA are being sold with the same filters. Ergo, MQA is lying about using "DAC specific" filters to reduce smearing on the DAC end. 

 

do they claim all filters are DAC specific?

 

maybe some are & some aren't

[mansr]

21 minutes ago, Ralf11 said:

do they claim all filters are DAC specific?

 

maybe some are & some aren't

We measured all of them.

[jabbr]

6 minutes ago, Ralf11 said:

 

do they claim all filters are DAC specific?

 

maybe some are & some aren't

Would be really really pointless if the filters aren't system specific.

 

In classic systems analysis an impulse response defines a point spread function which is used to generate a deconvolution which regenerates the impulse (this is deblurring). In the frequency domain this is a simple matrix division.

 

In the 1980s we were able to image fluorescent microspheres with 3D optical microscopy to generate a deconvolution that was able to "deblur" images such that DNA supercoils could be optically imaged.

 

Today, room correction works on the same principle limited only by resolution/deconvolution matrix size.

 

By this process end-to-end playback correction is accomplished which takes into account individual DAC, amp, speakers etc. -- results are all in the implementation but the math is real.

 

In any case if the filters aren't DAC specific then what is the point? You can always deblur the audio file with a deconvolution/filter applied during mastering and then a second applied per each playback system.

[Ralf11]

well, if mansr measured every filter for every DAC (??) then MQA is pointless - true?

 

I also need to speak to you about fixing som back-focused puppy pics...

 

 

[mansr]

7 minutes ago, Ralf11 said:

well, if mansr measured every filter for every DAC (??) then MQA is pointless - true?

With Archimago's help, all the filters on the Dragonfly and Mytek Brooklyn have been measured. Both match the Bluesound filters very closely.

[Ralf11]

so maybe they mean some of the filters are DAC specific

 

it's possible, right?  or did they say "all known DACs" or...

[mansr]

It wouldn't make sense to adjust only some of the filters per DAC. Each filter should be the combination of the ideal response with the per-DAC correction. Once the correction is known, why would you not apply it to all the filters? Besides, we measured all the filters on two different DACs.

[jabbr]

1 hour ago, mansr said:

It wouldn't make sense to adjust only some of the filters per DAC. Each filter should be the combination of the ideal response with the per-DAC correction. Once the correction is known, why would you not apply it to all the filters? Besides, we measured all the filters on two different DACs.

 

If the desire is to improve mastering, then one could “deblur” the master. That seems to be 1/2 the MQA promise. That can easily be done without MQA it can even be done entirely in the “DSD” domain, or PCM or whatever.

 

The other 1/2 the MQA promise seems to be per DAC corrections and you’ve shown this false.

[PeterSt]

11 minutes ago, jabbr said:

The other 1/2 the MQA promise seems to be per DAC corrections and you’ve shown this false.

 

Of course this was meant to say : the best filter (out of 32) for the DAC of concern.

Right ?

 

[jabbr]

11 minutes ago, PeterSt said:

 

Of course this was meant to say : the best filter (out of 32) for the DAC of concern.

Right ?

 

So we should really be talking about MQA vs Izotope? Is that it?

[mansr]

Just now, PeterSt said:

Of course this was meant to say : the best filter (out of 32) for the DAC of concern.

Right ?

I don't know what he meant to say, but the choice of filter number is done per track, presumably based on the spectral content, at the encoding stage. The DAC then applies what is allegedly its version of the indicated filter number on playback. From the official explanations, one is led to believe that the actual filters applied by the DAC are tweaked such that a given filter number provides the same analogue output response on every DAC (the "end-to-end" spiel). The measurements and firmware dumps we've done suggest that there is in fact no such per-device tuning.

[jabbr]

I’m glad you are delving into these details (honestly). I’m still trying to determine if there is anything unique and the best I can tell is that it may relate to effectiveness of compression — which is fine.

 

If the filter is preselected and then intended to be applied at the DAC without being customized for the DAC then I am saying this filter could easily be applied post mastering.

[mansr]

3 minutes ago, jabbr said:

I’m glad you are delving into these details (honestly). I’m still trying to determine if there is anything unique and the best I can tell is that it may relate to effectiveness of compression — which is fine.

 

If the filter is preselected and then intended to be applied at the DAC without being customized for the DAC then I am saying this filter could easily be applied post mastering.

We're talking about the interpolation filter used by the "renderer" when upsampling from 96 kHz to whatever higher rate it feeds the DAC chip.