From sampling theory we know that content above 22.05 kHz will alias ("fold back down") if sampled at 44.1 kHz. The only way to be able "unfold" that again is by destroying information in the 0 to 22.05 kHz band (which includes the audio band... where the actually audible stuff is stored) beforehand. MQA does this down to leaving only 13 bits of information intact. The freed up bits are used to store the aliased content and nothing else. Actually, this ultrasonic content goes through another lossy compression algorithm...
It's a spectacularly bad compression scheme. Even the "high-res" variant is pretty poor. It takes up more space than a "mid-res" FLAC file while delivering lower fidelity at the same time.
Do we have any proof of this? Because I haven't seen that to be true.
This thread really isn't about MQA, but well... You can watch Amir's
video about an example MQA file. The file clearly shows that MQA raises the noise floor above 15 kHz and - in this range - seems to encode information used to reconstruct ultrasonic stuff. That clearly demonstrates, that information in that (audible) range is lost, albeit at a very low level. As the MQA compression has been shown to be lossy, that information can't be fully recovered by "unfolding" the file. Equally, the reconstructed ultrasonic content is incomplete and lossy.
The advantage of "smoother filtering" you might get by using HighRes files can equally be achieved by upsampling, without destroying parts of the audible information by using MQA. I further haven't seen any controlled study that proves the audibility of the "phase and ringing artefacts" you mention.
The fact that some MQA files on Tidal might sound better to you or me is most likely explained by the fact that they're using a different master. The same master could just as well be delivered in 44.1 kHz / 16 bit without a lossy compression.
I am not sure about this. Honestly when recording in 24/44.1 or 24/192khz with my phone or camera in videos; the audio is way clearer with much more depth. This is the case for both racing videos and musical ones. So there is definitely something there which allows the audio to be much clearer. So this entire concept that 16/44.1 is the best ever, just doesn't hold water with me with my own personal testing. I know that most people have never tested a damn thing in their life and like to instead just listen to what other people say, but I for one don't give a damn what other people say and like to test things for myself.
In my experiences the MQA tracks on Tidal which are actually high res; sound better than the non-high res versions. The 16b versions sound no different than the "hifi" ones which sound no different than Spotify.
Personally I have listened to plenty of FLAC's and I haven't heard a single one that at 16/44.1 sounds better than Spotify on "Extreme" or "high" (since the definition of their highest quality changes depending on device) which is 384kbps OGG VBR Q9.
The other reality is that most music is recorded like shit; if you listen to music recorded more than 20 years ago.... 99% chance it is recorded like shit. Why do you ask? ADC's were shit, DAC's were shit. Therefore the performance was shit.
No matter what you swear about; it doesn't change reality and facts. The actual distortion properties in that music at the time of recording are probably around 80 SINAD... so it doesn't matter if your entire stack can deliver 120 SINAD (which is impossible since as we have seen from headphones, they are just in the 90 SINAD territory) you can't hear things which aren't there.
Now with that being said; it doesn't mean that music recorded a long time ago can't sound good... One of my favorite albums is The Bill Evans Trio Live in the Village Vanguard in 1961. It is well recorded and even small background noises can be heard... however the noise floor can be heard as well even with the "remaster" (so I am sure SINAD < 60).
So this is a topic that can be argued about literally forever... however in the few studios that actually know how to record music using modern hardware (and not the 95% of idiot studios recording with 20 year old "r3db00k iS b3St" mentality) the music CAN sound better and can take advantage of modern DAC's and Amps to an extent.
These facts are part of why the audiophile community isn't very large, especially amongst younger people. Since most peoples phones can output sound that is "good enough" for most "modern" recorded garbage (especially the modern pop crap recorded @ 0dbfs or even +1 dbfs) and even if you buy nice headphones.... the differences aren't huge for lots of stuff...
However it depends on your musical tastes and what you care about... as there are lots of well recorded tracks going back half a century for you to enjoy.
When I see everyone gushing over the newest "high SINAD" device I laugh a bit to myself because while it is "cool" it means nothing for audibility and it hasn't for quite a while. I just spent the last 5 years listening to a 1st gen DX7 (SINAD ~108) through a O2, THX 789 & Geshelli Archel2 Pro and "upgrading" to a D70s/SMSL SU-8S does NOTHING. The only thing I 'gained' was MQA and this is after I experienced better audio quality from CERTAIN MQA tracks on Tidal... there are a few CDs from artists who do high quality recordings that have these higher res MQA tracks on TIDAL that really are better than anything else available for streaming.
People who decided to hate on MQA and tell me I should buy FLAC's have no idea what it is like to work all day and listen to music... I would need $10000+ worth of music. To me ... I won't pay $1 for music basically ever. I just don't care to buy it unless it is a small artist i see in person that I want to support directly. I can't imagine wasting the price of a car on music and needing to spend basically hundreds a month buying more. I use streaming services every day and for someone like me; MQA has a benefit for a fair price... the cost of an MQA DAC isn't really much more (or sometimes even less) than non MQA DAC's.... so I don't really understand all the hate... if it solves problem then it solves a problem.
If you understand computers, streaming services and bandwidth then you would understand exactly why and how the concept of something like MQA was created... much like HEVC / x265 / h.265 where data is saved for better quality at a lower overall data cost... the amount of $ saved in bandwidth costs (nevermind the ability to expand your services without paying for more bandwidth) is more than worst the licensing cost.