My Questions and Answers (MQA): An Interview with Andreas Koch

[mansr]

1 hour ago, Fitzcaraldo215 said:

However, one must always consider the source.  Koch has been and is a huge advocate for DSD, while Stuart et al have been major detractors of DSD for over a decade.  It is not just about commercial interests.  I think these guys are really dug deeply into their respective philosophies, aka, beliefs.

Where in the article does he promote DSD?

[mansr]

32 minutes ago, Fitzcaraldo215 said:

He does not.  But, if you understand his background at places like Sony and Playback Designs, the picture becomes clearer.  

For Example, check this out:

http://www.audiostream.com/content/qa-andreas-koch#3W4VMkmY6ebX5v80.97

So his arguments against MQA are somehow invalid because he has expressed pro-DSD views elsewhere?

[mansr]

12 hours ago, jhwalker said:

It is supposed to make it better, by correcting any smearing in the time domain caused by the original analog to digital conversion, as well as improving the time domain performance in the receiving DAC.

There is no evidence to support that it actually does any of this.

[mansr]

17 minutes ago, Jud said:

Possible that it uses a reasonable apodizing filter at the ADC end, which permits the crappy filtering at the DAC end to cause less harm?

And how does that accomplish "deblurring" or any of the other feats of magic they promise?

[mansr]

2 minutes ago, Jud said:

I take from this that it's possible. 

"Feats of magic" = marketing bunkum

"Deblurring" = marketing rebranding of what any decent apodizing filter does, helping to remove ringing

An apodizing filter works by using an early roll-off to remove the high frequencies that would otherwise cause ringing. Removing high frequencies is the opposite of "deblurring" for any reasonable definition of common words.

[mansr]

1 hour ago, Fitzcaraldo215 said:

Nope, not what I said.  I just cautioned considering the source.  I would suggest similar caution if Bob Stuart or Mark Waldrep were to criticize DSD.  And, so on.

An argument should be evaluated on its own merits regardless of who made it. Only in cases of argument from authority does the person enter the picture.

[mansr]

1 minute ago, Jud said:

One ironic aspect of this is that mansr used Stereophile's measurements/graphs for (IIRC) the Explorer DAC in at least one or two of his comments.  In the magazine, the DAC's measurements were, if I remember right, described as "superb," whereas mansr's evaluation was not so, shall we way, ebullient.

 

That was Miska, although I agree with his assessment.

[mansr]

4 hours ago, Fokus said:

These are recordings off the output of a Meridian Explorer2, done at 192kHz. The HF bump is the combined modulator noise of the E2 and my ADC (a PCM1804).

 

Both traces are from the first track of Lemonade.

 

Red is the standard Tidal file, which plays at 44.1kHz. You see that the treble is cut off

sharply at 21kHz (which is a bit unusual for a modern recording, due to the use of half-band

ADC AA filters or downsamplers the spectrum more often runs flat to 22kHz).

 

Green is the MQA Tidal file, decoded by the E2. Again the treble cuts off at 21kHz, and rises again

above 23kHz. The part of the spectrum between 23kHz and ~36kHz clearly is an image of the baseband between and 8 and 21kHz. Strictly speaking, this is added distortion, and quite similar to the output of a NOS DAC.

From the Stereophile Mytek measurements it is known that the MQA replay filter is rather lazy and does not cut in below 22kHz, so it is not apodising at all, only passing along a lot of imaging.

 

 

This result indicates that the input to the MQA encoder was 44.1 kHz. The HF hump is actually shaped dither added by the MQA decoder. DAC and ADC modulator noise should at most reach -120 dB.

 

Could you send me a capture of 10 seconds or so from that track? I'd like to see exactly what filter configuration they're using here.

[mansr]

43 minutes ago, Fokus said:

1) Of course it is 44.1kHz. That is what Jud asked for, above.

 

2) Get the PCM1804 datasheet. It really is my ADC's modulator noise.

 

That ADC does indeed have a lot of noise. None of mine have anything near those levels. If you had a better ADC, you'd notice the MQA decoder adding dither with roughly the same noise profile. A firmware bug in the E2 makes it stay in this mode until power cycled after playing an MQA file.

 

43 minutes ago, Fokus said:

 

3) You can have two fragments:

 

samp1

 

samp2

 

Sorry, apparently I wasn't clear. I wanted a digital capture of the undecoded MQA stream.

[mansr]

5 hours ago, PeterV said:

High-end audio systems often sound better with analog recordings than with digital ones. The temporal decay is one of the few points at which analog systems beat their digital counterparts and it is therefore a very important parameter.

That statement cost you whatever credibility you might have had.

5 hours ago, PeterV said:

Any audio system has the tendency to 'smear out' the the signal both in amplitude and time, which always leads to a degradation of the original sound.

Digital PCM recording requires a very steep low pass filter before digitization to alleviate aliasing. Such a filter introduces anomalies including ripple, resonance at the cutoff frequency, oscillation (ringing) phase shift and high frequency loss.

Normal microphones have practically no response above 50 kHz or so. With a sufficiently high sample rate, you thus don't need much of an analogue filter at all. 192 kHz is plenty, and even 96 kHz is enough in most cases. Of course, modern ADCs are sigma-delta designs operating at several MHz followed by a digital low-pass filter. The problems you allege simply do not exist.

5 hours ago, PeterV said:

CD quality has a temporal blur of 5 ms, 24/192 1/10th of CD (500 microseconds), but MQA has found a method to reduce this to 10 microseconds throughout the entire digital encoding and decoding chain.

Oh, no. Not this again. CD has a temporal resolution of a few picoseconds. We discussed this at length not long ago. Here's a post from that discussion where I demonstrate timing accuracy of 44.1 kHz audio much better than what you suggest:

My scope doesn't have picosecond resolution, and even if it did, noise in the DAC would make it impossible to measure such small differences.

5 hours ago, PeterV said:

Nowadays, such anomalies can be overcome by using oversampling techniques or by using another format like DSD. But it is a fact that all digital recordings in the 80's and 90's intrinsically are degraded by these influences and even nowadays 24/96 recordings are, since filtering can severely degrade the temporal behaviour of audio systems.

 

So..let's focus much more to this beautiful aspect of the new algorithm.. MQA is capable to repair the temporal blur of PCM recordings to a very large extend. It is therefore capable to restore the original sound of the Recording and not just that what has been stored on the final Mastertape. MQA enhances the temporal decay of the recording significantly and this is audible to everyone.

 

Every serious audiophile should first listen to MQA and make up their mind based on what they hear, feel and experience instead of judging the technology beforehand, based on speculative publications.

 

MQA is for sure not a fraud or just a pseudo MP3 compression tecgnology. It is a paradigm shift and a new, disruptive technology.

 

This is the reason why not everyone is happy with its existence and fear is firing up rumours and aligations. That is a shame, since it will be much wiser to embrace this stunning innovation and make use of it.

How much are MQA paying you to post this?

[mansr]

6 minutes ago, Jud said:

I don't understand the predilection to personally attack someone who read some MQA marketing, heard something he liked, and consequently believed the marketing.  

I see no problem with pointing out the blatantly wrong.

[mansr]

24 minutes ago, Jud said:

That isn't all you did, as you're quite aware.  Hmm, and you're the one who just told someone *else* his credibility was suffering.

When people repeat that old fallacy about the temporal resolution of sampled signals, it casts doubt on everything else they say. I see no irony in pointing this out.

 

Perhaps I accused him of being a paid shill too hastily. His post sure made him sound like one, but maybe he's merely unusually gullible.

[mansr]

Just now, Fitzcaraldo215 said:

I agree, Koch is brilliant.  But, so is Stuart.  They just happen to disagree.

 

The annals of history are filled with brilliant men who just disagreed:  Edison and Tesla, Newton and Leibniz, me and my high scool teachers, etc.

History has shown that Tesla was right, but Edison had the better PR machine, just as Stuart does now with MQA.

[mansr]

28 minutes ago, Jud said:

Just wanted to note before we get too carried away with how much we don't know, that the scope of a patent is restricted to what is fairly disclosed.  So anything MQA wants to have protected as its intellectual property must be disclosed in the patent.  There is certainly an art to such "disclosures," but it does mean that what MQA actually does is very, very unlikely to be entirely divorced from what is mentioned in the patent (otherwise why bother to obtain it?).  It isn't a cookbook and doesn't need to be, but the general nature of what MQA does is pretty clear.

The full MQA process probably also includes elements not invented by them and thus outside the scope of their patents.