MQA is Vaporware

[Charles Hansen]

7 hours ago, George Hincapie said:

 

Isn't that the quality you get with Tidal? And if you can stream, why would you want to download? Seems pointless...

 

Hi George,

 

No Tidal rents three different quality levels of files. For 10 units (dollars, pounds, euros) you get MP3 lossy music. For twice that much money you get CD-quality (44/16) files, with a few hundred MQA quality files thrown in. For now those small number of files don't cost more, but since MQA is not a charity, it would be unrealistic to expect that to last forever.

 

An MQA file is a pseudo-high-res file. Most start off as 96/24, a few as 192/24, and even a few as 44 or 48/16. With the 24 bit files, the bottom 7 or 8 bits are discarded, and for sampling rates above 96kHz, the audio data above 48kHz is also discarded. (That is how they achieve their smaller file size.) So the easiest way to think about MQA is that it is a lossy version of the original true high-res file - kind of like an  MP3 of a high-res files instead of an MP3 of a 44/16 file.

 

Many people like to either purchase physical discs or downloads, simply because that is something they own. It only takes a few minutes to rip a physical disc, and then one always has a backup copy that is not prone to (inevitable) hard drive failure, plus the artwork and liner notes are very nice. Even downloaded files that you own are easily backed up onto another hard drive, plus once you own the music you can put it on all of your devices - phones, portable players, household networks, whatever. On top of that you don't have to worry about losing your favorite music when the streaming service goes out of business, nor do you have to worry about them raising your rates - ever.

Remember when cable TV first came out and it was just HBO and Showtime for $20 a month and no commercials? Now most people pay around $150 per month for their cable, plus you are stuck watching more commercials than they ever dreamed of on broadcast TV. Why? Because they can and you have little choice. Most people don't like watching re-runs all the time, but most people like listening to their favorite music dozens, hundreds, or even thousands of times. That's when it makes sense to own it.

I know a lot of people who use Spotify free (with ads) just to discover new music. When they hear something they like, they will just by the CD. New CDs are typically under $10 and used ones are typically around $3.

Hope this helps!

[Charles Hansen]

11 hours ago, Les Habitants said:

I'm a  new member, first post here. Considering streaming and maybe a new DAC soon.

 

So far I do not like really anything I see about MQA, maybe I'm missing something? Is MQA really only relevant to Tidal users?

 

Welcome, Les Habitants!

Yes, for the moment Tidal is the only meaningful source of MQA-processed files. Apparently there are somewhere around 2500 albums that have been had MQA processing applied. All of the current ones have been processed by MQA themselves, so that represents a big bottleneck as far as releasing more titles.

There is a rumor that Warner (one of the "big three" record labels, the other two being Universal and Sony) have had two of their own mastering engineers trained in applying the MQA process, but to date there have literally only been a handful of new MQA releases since March.

 

There is also talk of HD Tracks (the US-based high-res download store) starting a streaming service this fall that will only stream MQA files. That doesn't make sense to me, as the entire point of streaming is to have access to a vastly larger catalog that one is likely to ever own. As with all things MQA, I think we will have to wait and see what actually happens with the proposed HD Tracks streaming service.

 

The overall opinions are all over the map regarding MQA's sound quality, but the general consensus seems to be that it sounds "better" the CD-quality (44/16) but not as good as true high-res. This makes sense, as an MQA file made from a high-res master essentially provides 96/17 performance. Currently there is no extra charge on Tidal for the small percentage of albums available in MQA, but that is likely to change if MQA ever becomes a significant fraction of the catalog. The math is very simple - it costs more to produce, store, and stream an MQA file than a CD-quality file, so sooner or later that cost will be passed on to you.

 

When purchasing a new DAC, it seems to me that there isn't much of a motivation to buy one that is "MQA certified", as both the Tidal player app and the Audirvana music player will perform the "first unfold" to give MQA's 96/17 performance level with any DAC in the world that can accept 96kHz data. The second step that currently only happens in an "MQA certified" DAC is to adjust the coefficients of its digital filter. This will have a relatively minor effect on the sound, but there are other ways to get there besides buying an "MQA certified" DAC. Auralic has released new firmware for at least some of their products that are claimed to emulate the digital filters used by MQA DACs.

 

Other than that, the way to reach the closest approximation of the "MQA certified" digital filter coefficients is probably to purchase a DAC that has both "slow-rolloff" and "minimum phase" options for the digital filter. Many DACs have one or the other, some have both. Some are user-selectable,  and some just come that way from the factory.

 

If you are a fan of both streaming and high res, perhaps the best option is to use Qobuz for streaming. It's not currently available in the US without signing up through a proxy server, but they have three service tiers - 10 units (pounds or euros) for lossy, 20 units for CD-quality, and 29 units for true high-res, along with deep discount on purchased files. Apparently Qobuz has a much larger catalog selection than Tidal (especially for classical), although for pop music I don't think anybody compares to Spotify. There are persistent rumors that Spotify will offer CD-quality sometime this year.

 

As usual, the best way to select any new audio product is actually listen to it - preferably in your own home system using the music that you know and love.

 

Hope this helps,

Charles Hansen

[Charles Hansen]

41 minutes ago, Les Habitants said:

Thanks again Charles, it will be interesting to see how this plays out.

 

Yes, I agree. I really don't understand the whole streaming business model. The artists make next to nothing. No streaming service anywhere has a made any profit to date. Yet steaming is the fastest growing segment of the entire record labels' income. Someone like an Apple can afford to lose many tens of millions of dollars per year on streaming and/or downloads, because they make it up 10x over in sales of their highly profitable hardware devices.

 

But the only way I can ever see streaming be profitable for everybody is if the rates roughly double. Yet how can they double the rates and not lose customers? I'm guessing that the record labels are willing to let MQA spend tens of millions of dollars to throw stuff at a wall. Now they are sitting back to see if anything sticks. For example if adding MQA doubled the rate of Tidal's premium (CD-quality) subscribers, the labels would back it to the hilt.

 

Otherwise I'm guessing it will end up like Neil Young's Pono - the record labels focusing on the wrong things and trying to charge outrageous prices for the customer's 3rd or 4th purchase of the same title. They never even understood back in the '90s that Napster was responsible for record high CD sales levels. It gave customers a cheap and easy way to listen to new music, and when they liked it, they would buy the much better sounding disc. I seem to recall some statistic such as a heavy Napster user typically spent 80% more per month on music than non-Napster users. Admittedly the situation is different these days:

 

1) The average person has become used to poor sounding MP3 files.

2) The average person can no longer afford to spend $50 or $100 per month on luxury items like music.

3) The average person doesn't ever actually sit an listen to music. They just play a recognizable noise from their phone to distract them from their unsatisfying jobs.

 

Many music lovers I know subscribe to Spotify, as it has the largest catalog and best UI. The sound quality isn't marvelous, but they just listen to it as background music and when they hear something they like, they just buy the CD for $10 new or $3 used. Then they rip it to any and all playback devices and have a safe backup copy complete with liner notes and lyrics and so forth. Redbook CDs can  sound surprisingly good. High-res is just the icing on the cake.

 

Cheers,

Charles Hansen

[Charles Hansen]

9 minutes ago, #Yoda# said:

The labels don't want to sell their "crown jewels", the masters in high, or in best case the original resolution and format as reproducible FLAC/WAV/DSD files, finally. So MQA is a very welcome solution to solve this issue, even if there is no DRM mechanism implemented for now. When all the hype about MQA is obsolete one day, the labels can sell them a 2nd, 3rd time in real 24/96 and eventually again in 24/192 coated as remaster and perhaps for those who really think, they still can realize a difference, in DXD.

 

Hello Yoda,

 

Spot on, in my opinion. In 1989 the record labels (there were far more than just 3 back then) all simultaneously colluded to pull the plug completely on vinyl, despite it still having a 33% market share at the time. At $8 per LP, CD was vastly more profitable. Nearly 30 years later they are again happy to sell vinyl - at $30 per LP and $50 per "audiophile quality" LP.

 

If MQA takes over, once the hoopla dies down, I'm sure the record labels will be glad to sell the true high-res masters - but this time at $50 to $100 each. History likes to repeat itself.

 

Cheers,

Charles Hansen

[Charles Hansen]

3 hours ago, #Yoda# said:

fortunately there are still some beacons of customer and music oriented behavior. Some artists are selling HiRes albums in best resolution as FLAC download in their web stores and some indie labels noticed the signs as well.

 

Hi Thomas,

 

Yes, one of my favorite artists is Sam Phillips (not Elvis's producer, but a female singer songwriter). She won a Grammy and then faded to obscurity. Her online shop sells things all the way up to 96/24 FLAC files - I think mostly because I helped sway Michael Hobson of Classic Records (another Sam Phillips fan) to re-issue her popular albums in high-res digital. But a lot of her offerings are unfortunately only in MP3. Still she's a fantastic artist and when selling semi-direct (there is some sort of fulfillment house in the middle), she probably makes enough money on music sales to stay alive. I think she still does live shows (I've only seen her once), but largely only in the LA area.

 

Clearly the times they are a changin' and the old ways don't work well in the new world. Cheers!
Charles Hansen

[Charles Hansen]

12 minutes ago, #Yoda# said:

 

My first thought was your friend and ex business partner Neil Young with his store https://neilyoung.warnerbrosrecords.com/music-2/hd-digital.html

following his promise and philosophy to sell plain HiRes music and CD quality for the same price. 

 

Hi Thomas,

 

The store you linked is Warner Brother's store, not Neil Young's. There are other stores for other Warner Brother's artists as well. Neil Young's store was Pono Music, which was shut down when Apple purchased the digital file vendor, Omnifone. Omnifone was immediately shut down and all employees fired. Apple fan-boys say that Apple wanted some key patents that Omnifone owned. Neil Young fan boys suspect the whole thing was a cheap ($11 million) way for Apple to kill off the only other company in the world that supplied all 3 components required for a successful music enterprise - players, downloads, and desktop player software.

 

Pono only sold downloads in the highest available resolution. They had a "Pono Promise" that if any album purchased from Pono were released in a higher resolution that they customer would receive it for free. I don't think that ever happened, however - not because of Pono but because the labels didn't release any new versions of existing albums during Pono's lifetime.

 

Neil's position was that all music should be the same price, regardless of resolution. I don't think the record labels felt the same - if there were any justification for making more money, they didn't want to leave any of it on the table.

 

Cheers,

Charles Hansen

[Charles Hansen]

5 hours ago, #Yoda# said:

Hi Charlie,

 

anyway if it is a primarily a WB  or NY store, it is currently the cheapest way to buy NY records in HiRes. I know all the history, I was a Kickstarter backer for the PonoPlayer and we already had some inspiring talks in the Pono community.

 

I'm not really a NY fan boy, in fact, I bought the player because it's circuits has been designed by Ayre. I don't think it was Apples objective to prevent a new competitor. I would rather call it a collateral damage and the reason of failure had been primarily the financial effects of the PonoPromise, missing financial strength and several other management issues.

 

Anyway, the basic approach of Neil Young is correct, IMHO. The very most albums today are produced in 24/96 or even better resolutions and from a cost perspective it would be best to sell the HiRes masters originally to the customers. DR shaping to "Mastered for iTunes" and downsampling to redbook standard are additional costs but in fact, selling an original master in an open format like FLAC means to sell it finally. A "No Go" for the marketing guys. For this reason they are very happy to have an alternative like MQA and for the time beeing until this will be the standard, they put us off with 24/44.1 or /48 downgrades in best case. 

 

Cheers,

Thomas

 

Hi Thomas,

 

So you must be that Thomas! Good to hear from you. Everybody has a different perspective, but I think the main reason that Pono failed is because they didn't realize (as Apple does), that there is more money to be made in hardware than in selling software. I also don't think they understood that all digital sounded better or the Pono Player. There were a lot of people at Pono that thought it was all about the "high-res" files and that any player (from a $129 Fiio on up) could let you hear how much "better" high-res files sounded. (sigh)

I know they had to pay the labels extra for the "Pono Promise" but if there were only one or two free upgrades, it couldn't have cost them too much money - not enough to sink an otherwise well-run ship. YMMV.

 

Cheers,

Charles Hansen

[Charles Hansen]

2 hours ago, firedog said:

I and some others actually did get free upgrades to higher resolution versions of some albums when they became available.

 

Hi Freedog,

 

That's great to hear! It was a good deal and it made sense to the consumer, but I was out of touch for a long time and didn't know that any had actually been upgraded.

 

Cheers,

Charles Hansen

[Charles Hansen]

2 hours ago, mcgillroy said:

Can anybody explain me the economic or other rationale of Stereophiles MQA unconditional endorsement?! Today another DAC review is up that sings the song of MQAs qualities.

 

More importantly even goes so far as to hit competing vendors for not including MQA:

 

"If you were contemplating the purchase of a new DAC, why would you not want it to include MQA processing?"

 

and

 

"Schiit's reference DAC would be my reference DAC—if only it had MQA"

 

etc, etc.

 

Audio reviews are audio reviews but this level of ignoring the wider discussion and including specific vitriol is astonishing. Why?!

 

For what it's worth, many Stereophile writers (including editor John Atkinson) actually engage with the general public on questions like these at:

 

https://www.audioasylum.com/cgi/etv.mpl?forum=critics

 

Might be worth asking him directly there.

[Charles Hansen]

Hello All,

 

I think some very astute comments are being made that deserve a response from Sterophile and/or JA. As noted before he does not seem to participate in this forum, but he is almost always quite responsive to queries posted at:

 

https://www.audioasylum.com/cgi/etv.mpl?forum=critics

 

Each forum has different rules. The rules at The Audio Asylum are fairly simple - if one has any affiliation with the audio industry in any way, you agree to use your real name and disclose your affiliation.. Manufacturers are not allowed to reply to general questions (eg, "What CD player should I buy?") but can respond to specific questions about the equipment they manufacture (eg, "What is the power consumption of an Ayre CD player?"). Sign up is free and easy.

 

Cheers,

Charles Hansen

[Charles Hansen]

3 hours ago, The Computer Audiophile said:

 

But not cryogenically treated?

 

Chris,

 

Why the snarkiness? The only difference between the original Berkeley DAC (your long time reference) and your even more beloved "Reference Series" (at nearly 3x the price) was upgraded passive parts quality - things that shouldn't make a difference yet obviously do to a trained listener with a familiar system playing familiar music. Specifically, a chassis machined from solid billet instead of bent sheet metal and a change from "standard" FR-4 PCB material to Rogers 4000 series, a low-loss material designed for GHz range circuits.

 

I think this is more than enough about who can hear what differences, and is certainly not the place. Please return to discussions about MQA.

 

Thanks,

Charles Hansen

[Charles Hansen]

1 hour ago, The Computer Audiophile said:

There's actually much more that's different between the Alpha and RS. 

 

Chris, you are correct - I was exaggerating to make the point that passive components make a difference and I should not have. Apologies to all. Also I was working from memories of old photos that did not have the resolution of some newer photos that have since been posted. The RS added a shielded daughterboard module to the in addition to the other changes in the passive parts. There are a good set of comparison photos here on this thread, along with an interesting introduction:

 

http://www.whatsbestforum.com/showthread.php?2740-ack-s-system-end-of-round-1/page11

 

The green power supply PCB on the left size appears identical but for the potted transformers (same brand), and the only other visible change is that the AC line fuse goes from glass to ceramic. The main audio/digital PCB changed from the typical green solder mask to a clear solder mask on the (expensive!) Rogers low-loss PCB material that has a very distinctive appearance. All of the circuitry and parts for the analog stage appear to be completely identical.

 

The only other difference I could see at the time was the addition of a a small daughterboard near the left-front corner of the main PCB. I'm sure that it also had an effect on the sound quality (perhaps a more powerful chip for the digital filter?). The daughterboard sits above the main Analog Devices DSP chip. There have been two other changes which I did not see when I first looked at this a few years ago with lower-res photos:

 

1) There is a grey ribbon cable coming from the front panel PCB that connects to the main PCB near the DSP chip. On the original, nearly all of the traces from that connector angle off to the left, whereas on the RS most of the traces head straight back (hidden underneath the daughterboard and its shield). So they may have also changed the DSP chip in addition to adding the daughterboard.

 

2) The master oscillator was changed from an unknown brand to the Crystek especially designed for audio - although the oscillator's power supply and support circuitry remained identical.

 

The main point was that many of the changes only applied to the quality of the passive parts (expensive PCB material, expensive solid billet chassis, potted power transformers, and a ceramic AC fuse - a "superfuse"?).  Without working at Berkeley it would be virtually impossible to rank the relative sonic importance of the changes made to the passive parts to whatever function the daughterboard provided and the difference created by swapping crystals.

 

However the only change that might have been made for purely cosmetic reasons would have been the solid-billet chassis. I've never done a completely fair test where the chassis was the only difference to see how much of a difference it makes. But surely Berkeley would not have made changes to the (essentially invisible) passive components unless the improvements in sound quality were appreciable. For example, just the change in PCB material would be at least as expensive as the added daughterboard.

 

Cheers,

Charles Hansen

 

 

 

 

[Charles Hansen]

2 hours ago, jabbr said:

 

Ha ha, that's fine. We have such an amazing ability to measure small differences that it really interests me regarding what the limits of human ability to distinguish really are. The suggestion that Rogers 4003 or whatever might sound different than FR4 PCB opens up a lot of questions for me, like : wow, how do we hear that?

 

On the other hand, if really good modelling was done you ought be able to account for the dielectric differences so perhaps its just a more optimized design?

 

Those are really great questions. I've done a lot of listening tests to different PCB materials, trying to correlate the sonic differences with measurable differences as provided in the datasheets. I've been able to reach some general conclusions but only have "hand waving" justifications.

 

I think what we will find is that our current understanding of the ear/brain hearing mechanism is woefully incomplete. A good example of this can be read in a book called "The Secret of Scent" by Luca Turn. A fascinating read (and possibly a bit of a struggle if you've never studied chemistry, especially organic chemistry (which involves carbon and is the basis for all life). In it he shows that the commonly-accepted "lock and key" model for how the nose works is completely incorrect, even though that has been "conventional wisdom for nearly a century.

 

Instead it turns out that olfactory nerves do not sense the shape and/or charge on molecules - they "listen" to the vibrational frequencies of the molecule's side chains, using tiny spectrometers. These spectrometers are so small that to fit into a human cell that they only work on the principles of quantum mechanics. (QM was only proven to be correct in the mid-'90s and is the really weird physics where solid objects can pass through each other, two particles can be in the same place at one time, and the transmission of information is not bound by the speed of light - it can transfer instantaneously across any distance.)

 

As nature doesn't like to waste good, usable mechanisms, using the same things not only across different species but even across different kingdoms, I will be surprised if it turns out that the ear/brain does not use QM. Here is an article that shows us just the tip of the iceberg on how incomplete our current understanding is: Human Hearing Outsmarts Physical Limits | Evolution News

 

Cheers,

Charles Hansen

[Charles Hansen]

6 hours ago, Ralf11 said:

https://phys.org/news/2015-06-controversial-theory-olfaction-deemed-implausible.html

 

 

I find phys.org to be an xlnt news site - I was told about it by a barista (who is now in physics grad. school, where he will be well positioned to save the world)

 

"All truth passes through three stages. First, it is ridiculed. Second, it is violently opposed. Third, it is accepted as being self-evident."

Arthur Schopenhauer
German philosopher (1788 - 1860)

 

Back to MQA as Vaporware.

[Charles Hansen]

12 hours ago, fung0 said:

As a journalist who's spent decades reviewing all kinds of electronic equipment, including audio gear, I can offer some perspective.

 

Hello Fung0,

 

Excellent article with a very detailed and informed perspective.

 

Best,

Charles Hansen

PS - Is that you Leo?

[Charles Hansen]

13 hours ago, fung0 said:

 Companies don't offer bribes as such (if only!),

 

Hello Fung0,

 

While I agree with your very well articulated premises for most publication. I am fairly certain there are exception to the above quoted sentence.

 

I know of at least one US print magazine and one US webzine that allegedly only review equipment if you advertise. (They may occasionally break their own rule, so as not to make it too obvious.) Advertisers are allegedly guaranteed good reviews, and the more valuable the ad contract (size and frequency of placements, along with contract duration) allegedly the better the reviews will be. One publication allegedly took a loudspeaker company from start-up mode to major player  within 3 years, almost single-handed. One publication allegedly will sell cover shots to the highest bidder. One publication allegedly  will write lengthy positive reviews in exchange for non-financial incentives such as all-expenses-paid luxury vacation (which can be easily disguised as "travel expenses/reimbursements").

 

As you correctly note, the product being pimped must meet a certain level of performance (at least in the writer's mind) or else it would be too obvious and the reviewer/publication would lose credibility.. You will never see a mediocre product promoted in this way. But "sweetening the pot" can result in reviews that are more praiseworthy than would they would otherwise receive.

 

It's also well known that some manufacturers allegedly will not submit products for review to certain magazines. I think even Magnepan publicly acknowledges that they will not submit review samples to Stereophile, due to the fact that they do not measure ""well" under JA's loudspeaker test protocol. That is just one example and one reason.

 

Best, regards,

Charles Hansen

[Charles Hansen]

5 hours ago, mansr said:

It's not that simple. An ideal sinc filter has a perfect cut-off with no ringing or aliasing/imaging. Unfortunately, it is also infinitely long and thus unpractical.

 

Hi Mansr,

 

Actually that is not correct. An ideal sinc filter would be infinitely long and thus have infinitely long pre- and post-ringing.

 

EDIT: That is precisely why one must make tradeoffs between time-domain performance and frequency domain performance. An ideal sinc filter would have perfect frequency response, but terrible impulse response.

 

The only way around the trade off is to raise the sampling rate to the point that the tradeoffs are negligible. In the case of audio, a factor of 10x (200kHz) is sufficient, and192 kHz is close enough to that to get essentially perfect performance in both domains.

 

Hope this helps,

Charles Hansen

[Charles Hansen]

6 minutes ago, fung0 said:

I've certainly seen occasional extremes of collusion between publishers and vendors, as you describe. But I think you'd agree that, in general, influence is more subtle. We know there are 'paid shills' out there. But 'useful idiots' are far more numerous.

 

Hello Fung0,

 

Actually, unfortunately I have to disagree. There are only two audio print magazines in the US, and 50% is more than "occasional" in my book. There are far more online publications, and there I would agree with you - one known example and one or two suspected examples out of many dozens of websites is more in line with what I would call "occasionally".

 

EDIT: I agree 100% with all of your other points, I find them to be extremely insightful. To have the wisdom for self-reflection like that is rare, and I commend you for sharing your insights with the world in general. It will even have the honest reviewers and publications thinking twice about what they are doing.

 

Cheers,

Charles Hansen

[Charles Hansen]

2 minutes ago, rickca said:

The MQA business development team must love these publications.

 

Yes, it makes part of their job very straightforward. And they are not stupid people at all - quite the opposite, they are extremely clever. Any digital engineer will admit that the basic idea of "folding" the low amplitude high-frequency information under the LSBs of the baseband data is a clever idea. While one may have legitimate disagreements about the audibility of the choices made by MQA, it doesn't detract from the fact that they are clever people. Clever enough to manipulate the perceptions of the (to quote from the MQA annual business report) "key opinion makers in the music industry and journalists". Read the full report from last year at:
 

https://beta.companieshouse.gov.uk/company/09123512/filing-history/MzE3MzU2NDUyM2FkaXF6a2N4/document?format=pdf&download=0

 

The easily bought-off webzines don't apparently register among MQA's "key opinion makers", hence the need for unfair and/or misleading "comparisons".

[Charles Hansen]

33 minutes ago, fung0 said:

Sounds like the last survivors in print are being forced to make increasingly horrible compromises...

 

Thanks for your kind EDIT. I think about this stuff a lot - the whole problem of disseminating useful information to an appallingly gullible public. We have endless information a few clicks away, but most people seem no have no ability (or inclination) to discriminate between genuine insight and total hogwash.

 

Hello Fung0,

 

On the first point I would say "choose" rather than "forced". Nobody that I know of is holding a gun to their head saying, "Take this money or I'll kill you."

 

On the second point, I think it boils down to personality types. One common measure is the Myers-Briggs personality inventory. Two of the quadrants comprise about 20% of the population, and it seems that those are the ones that question "authority". The other 80% are content to just go along with things, as long as they are "comfortable" in a physical sense. It doesn't apply to just audio, but to politics, religion, or any other type of belief system.

 

Cheers,

Charles Hansen

[Charles Hansen]

14 minutes ago, Fokus said:

 

1) Mans probably meant that, given a band-limited signal, the replay Sinc filter does not ring. Which is correct.

But it sidesteps the issue of how to obtain a band-limited signal at the production stage.

 

2) Only if you are looking at the signal.

 

3) I repeat it once more: ringing due to excessive filter steepness is perfectly audible, but only if the ringing frequency falls within the subject's audible range, and the ringing envelope exceeds the envelope of the relevant cochlear filter for that frequency.

 

4) For most adults and CD rate or higher it is a non-issue.

 

Hi Fokos,

 

I took the liberty of numbering your points for easy reply:

 

1) Exactly. The easiest way is to sample at (say) 10x higher than the highest frequency of interest. Then no filtering is needed (at least in the case of audio. But since the CD standard was set as soon as it was barely achievable for a commercial enterprise, the problem is that there are many musical instruments with musical energy above 20kHz. One solution would be to omit the anti-aliasing and reconstruction filters altogether and live withe the aliases. Plenty of people own "non-oversamping DACs and that demonstrate that strict adherence to sampling theory is not required for musically satisfying results. Think about all of the good times people had in the 60s and 70s listening to their favorite songs on the AM radio with a maximum bandwidth of only 5kHz. How important are all the numbers anyway. Even FM radio was limited to only 15kHz. Numbers and specifications have little relationship to the actual listening experience.

 

2) It depends on the system and the listener. I can hear differences in blind testing, as can many others. However, in general you are correct. It requires training and/or sensitivity to hear these differences.

 

3) See #2.

 

4) See #3.

 

4 minutes ago, Fokus said:

And not invented by anyone related to MQA:

 

http://www.aes.org/e-lib/browse.cfm?elib=10276

 

Nice find! Thanks for the link. This shows that nothing in MQA is new. Not the "folding", not the minimum-phase slow rolloff filters - just the hype and the attempt to extort money through licensing and royalties. I guess they will patent anything these days.

 

Cheers,

Charles Hansen

[Charles Hansen]

2 hours ago, Fokus said:

As for your replies to 2)-3)-4): sure you can hear things. But was all else scrupulously kept equal? Not easy, that.

 

Hi Fokos,

 

My degree is in physics, and I've done real research in real labs on real projects. I am familiar with correct protocols and methods. My ability to hear many of these things only came with many decades of experience. Since this has been my job since 1985, I have more experience than most. As a manufacturer it is much easier to control the constants and ensure that everything is equal. For example when listening to different digital filters, all I have to do is mute the preamp, load new coefficients into the FPGA, and unmute the preamp. The DUT had a small toggle switch on the rear, to select between two sets of cofficients so we would load two sets of coefficients at once. I cannot reach the toggle switch from my wheelchair, so the other engineer would flip the switch for me. Nearly all of the tests were done blind. Sometimes we would load two new sets, but usually I would pick a winner and replace just the loser. I did this for 6 hours a day every day for 3 or 4 months and must have listened to many hundreds of sets of different filter coefficients, looking for patterns and trends. For example in every case (using mostly Redbook sources - high res sources were extremely rare back in 2009 - just a hand ful of DVD-Vs and DVD-As which were used to double-check) I found that regardless of the other filter parameters that minimum phase sounded better than linear phase. This was just one of eight or ten different filter parameters tested.

 

Obviously this type of thing is not available to a typical audiophile. All of the listening tests we perform are done with equal rigor.

 

Hope this helps,

Charles Hansen

[Charles Hansen]

8 hours ago, Fokus said:

That's not what I meant. Ringing gets loaded with many sins, but many comparisons change at least two factors at the same time. When MP wins, is it because of the eliminated pre-ringing (which exists only at Fs/2), or because of the phase distortion (which extends down into the audible band)? When a less steep filter wins, is it because of the reduced ringing, because of the drooping treble, or because of the increased levels of imaging?

 

 

Both of your examples contradict yourself, as you maintain that any ringing (or aliasing close to Nyquist) is inaudible. If we ignore the internal self-inconsistency, your question amounts to "How many angels can dance on the head of a pin?" The difficulty is that all the parameters you note are inextricably linked at a given sampling frequency. That is why I noted that the only way around the problem is to increase the sampling frequency up to around 200 kHz or more.

 

Hope this helps,

Charles Hansen

[Charles Hansen]

7 hours ago, mansr said:

1) That is exactly what I meant. An impulse is not band-limited.

 

2) No, regardless of the highest interesting frequency (20 kHz for audio), you need to sample at more than twice the highest present frequency. If you sample at 200 kHz without anti-alias filtering, and the input has a strong component at 399 kHz, it will alias to 1 kHz and ruin your recording. In practice, microphones have very little response beyond 50 kHz (most drop of well before that), so you can get away with sampling at 192 kHz, or even 96 kHz, using little or no filtering. Or you could if such ADCs existed. Audio ADCs are typically sigma-delta designs with a sample rate of 5.6 MHz or more followed by a digital downsampling filter.

 

3) For playback, yes. The image frequencies are above 20 kHz and thus inaudible. Omitting the filters when recording would result in ultrasonic frequencies being aliased into the audible range. On playback, letting the image frequencies go unchecked is also a bad idea, even if they are inaudible. Firstly, their presence can cause audible intermodulation products in amps and speakers, and secondly, burdening the amp and speakers with frequencies you don't want and can't hear can impact their performance at the frequencies you do want. A little inaudible ringing above 20 kHz seems rather harmless by comparison.

 

1) Real music made with real instrument recorded with real microphones are not band-limited to 22.05kHz either.

 

2) I am talking about the real world, not some imaginary one where one deliberately injects a high-frequency, out-of-band signal into the audio signal. Also, it is easily possible to downsample delta-sigma ADC's using filters that don't ring and instead emulate the bandwidth restrictions of a purely analog chain.

 

3) There is no difference in aliasing between recording and playback. Almost always half-band filters are used because they only require half the number of taps and therefore are half the price. Half-band filters are always down only -6dB at the corner frequency (Nyquist), and when used as anti-aliasing filters will typically let through some spectral content between Nyquist and about 24kHz (for CD). When played back with no reconstruction filter, the subsequent aliasing will be greater than about 20kHz.

 

The problem is that putting a steep, sharp filter into the chain causes audible problems. Putting two steep, sharp filters in the chain compounds the audibility of the problems.

 

On the other hand if no anti-aliasing filter is used, then the aliasing will extend to lower frequencies. If we assume that MQA music spectral distributions of music are accurate (they are actually not as they do not include any percussion instruments - just one of the many ways that MQA goes out of their way to mislead) then the musical spectrum is down -50dBFS at Nyquist and falls at roughly --40dB/octave above that. Aliasing at 10kHz would be about -72dBFS, so even a CD-rate system with no filters would have a very small amount of aliasing below 10kHz. One would have to listen to such a system to see which was the more objectionable problem - the insertion of two steep, sharp filters in the chain, or the presence of low leves of aliasing in the top octave. Many have found that eliminating just one of the filters (reconstruction) makes for an audible improvement. I know of no experiments where the antialiasing filter has also been eliminated.

 

Thanks,

Charles Hansen

[Charles Hansen]

Hi Mansr,

 

I think we're pretty much saying the same thing. The only area of potential disagreement is that you are implicitly saying that any noise above ~20kHz is inaudible with continuous sine waves and is therefore of zero consequence to human hearing. I disagree with that, based on my own direct experience.

 

At one time our top-of-the-line power amplifier was based completely on FETs - both J and lateral MOS devices. It had a  -3dB point of 100kHz. We made a new amplifier that had an output stage with an emitter-follower triple using complementary BJTs. (This is the so-called "T-Circuit" developed by Bart Locanthi and used by JBL and many others since.) When we listened to the first prototype (with a -3dB point of 170kHz, it sounded "shut in", "closed down", and "rolled off". By adjusting the compensation capacitors that keep the circuit stable with capacitive loads (unnecessary with lateral MOSFETs) such that the -3dB point was raised to 250kHz, the amp again sounded as open and extended as the previous amp did with only 100kHz bandwidth.

 

I have no explanation for this except to note that just because the ear/brain cannot hear continuous sine waves above ~20kHz does not mean that transients with waveforms steeper than that are not detectable by the ear/brain:

 

https://evolutionnews.org/2013/02/human_hearing_o/

 

Another area of disagreement is the audibility of aliasing. Clearly the higher frequency aliasing produced by only filtering one side of the record/replay chain should by itself produce less audible artifacts. But that leads to the necessity of using steep filters with sharp corners, which in my experience definitely produce more sonic damage that does high-frequency aliasing noise that is far below the background noise level of nearly all listening environments. I don't think there is any way to "prove" either standpoint is correct. There is such a wide variety of capability in listening capabilities due to years of intensive training (similar to skills of playing a musical instrument due to years of intensive training, that there will never be one "correct" answer. The best case would be to have a situation that applied to a particular percentage of the population. Otherwise we are left with the situation we currently have where many can hear the differences between (say) cables and many cannot.

 

But to insist that I cannot hear something just because you cannot also hear it is as silly as the doctor to tell me I am not in pain simply because he is not in pain. Or for me to tell a world class violinist that it is impossible to play Tchaikovsky's violin concerto simply because I cannot.

 

Hope this helps,

Charles Hansen