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God of SINAD vs. reality we get from most available music files

pma

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God of SINAD vs. reality we get from most available music files

There is a good thread here in ASR discussing the practical importance of SINAD number

which links to the original article at

Let me quote from that article:

“SINAD is short for “Signal to Noise And Distortion”. It’s the ratio between the signal - the stuff we want to hear, like the music we play - to all the other things we don’t want in the sound. It’s also sometimes expressed as THD+N, or “total harmonic distortion plus noise”, which is the ratio of the noise and distortion to the signal - the same thing the other way around.
As the name suggests, SINAD is a sum of two broad groups of things we don’t want in the sound: Noise, and distortion. Noise is just what it sounds like: noises leaking into your music, which can range from the “hum” of your AC power, to the “hiss” of white noise. There are a lot of potential sources of noise out there, and they can distract from what you actually want to listen to, particularly if you’re listening quietly.
Distortion, the other part, is similar to noise in that it’s an addition to your music. Unlike noise, however, distortion is produced by your music interacting with the flaws of the system. This means that distortion will be related in level to the signal causing it, whereas - as anyone who’s heard hiss on their IEMs will know - noise can be loud without anything playing at all.
This is the big trouble with SINAD: In some cases, a low score points to an amplifier or DAC that is just plain not working, but in others, it’s only catching “problems” that you won’t actually be able to hear.”


Obviously, the SINAD, or THD+N, which is absolutely same thing just with opposite sign, is not well understood or simply not understood in general public, as we can see from many threads here in ASR. Let me name a few:




SINAD is appealing for both inexperienced readers and technically oriented reviewers as it gives a single number that is used in simplified charts as a comparative measure of various audio products. As any simplification, there is a question if such simplification is good enough to be a basis of comparisons of audio products. It definitely tells something, but how would it be useful in a real life?

Let's thing, for a while, about music files that we use to feed our beloved audio chains. Streaming services yield files of unknown quality, regardless label like “lossless”, “hires” etc. File analysis often shows that such label is incorrect. In fact, well prepared “old style” 44.1kHz/16bit files are still a very good source of music and many so-called “hires” files and streams are just a re-sampled versions of original 44.1/16 versions. The other point to be mentioned is that a background noise during recording and microphone path noise are barely that low to utilize dynamic range of the 44.1/16 format. In fact, the best recordings only attack only 60dB range, and this is for classical music.

romanceforviolin.png


Popular music often sticks with something like 20dB range. So, there is a question, what SINAD we can get from 44.1kHz/16bit files, just in theory? And after processing by a DAC?

1. Analysis of 44.1kHz/16bit files with respect to achievable SINAD

SNR of 16bit full scale sine wave to the rms value of quantization noise in theory is:
SNR = 6.02N + 1.76dB

For N = 16 (bits) we get SNR = 98.08 dB, theoretical maximum

With 1kHz undithered sine in 44.1kHz/16 bits we measure

signal_44_16b_undithered.png


This makes SINAD = 97 dB, THD = -101 dB, but SFDR (spurious free dynamic range) is suffering at some 104 dB due to quantization noise and this quantization noise becomes audible at low level signals like -60 dBFS.

To get rid of spurious frequency components of quantization noise we add a small amount of noise called dither. Frequency independent TPD dither makes a good job of reducing THD, increasing SFDR at the expense of about 4.8dB loss of SNR. Spectrum of 1kHz TPD dithered 44.1kHz/16bit sine looks like this:

signal_44_16b_dithered.png


We get THD = -126.7 dB, SFDR of some 132 dB and SINAD = 93.3 dB.

There are attempts to use dither methods that are not frequency independent. They are based on assumption that noise is most audible in certain frequency range, so they reduce noise rms level below some 12 kHz at the expense of fast rise in noise energy between 12 kHz and 20 kHz. We call this noise shaping and the spectrum of 1kHz sine wave with noise shaped dither in 44.1kHz/16bit format looks typically like this:

signal_44_16b_shaped.png


We get THD = -104.1 dB, but SFDR of 102 dB and SINAD only 70.7 dB, measured over 22 kHz bandwidth without frequency weighting. Noise shaping is responsible for this huge SINAD loss and the reason is we have only 44.1kHz sampling, i.e. 22.05 kHz BW. Noise shaping would be more effective only at higher sampling rates like 96 kHz.

There might be an idea of resampling the 44.1kHz/16bit source file to higher sampling rate and using noise shaping, but once we have a 44.1kHz/16bit original file, a little to improve SNR or SINAD can be done, resulting only in one or few dB difference. No DAC with 130 dB SINAD would make any miracle here.

As a comparison, next plot shows all the previously discussed files – undithered, TPD dithered and noise shaped 1kHz sine in 44.1kHz/16bit format in one graph.

signals_44_16b_allinone.png



2. 1kHz sine waves in 44.1/16 format played through through an oversampling DAC, Topping D10s

Audiophiles, supported by popular audio reviewers, often assume that playing “low resolution” 44.1/16 format files through some miraculous oversampling DAC that oversamples at 384kHz/32bit will get something more from 44.1/16 files. Unfortunately, not really. We may get some tiny improvement in some cases, but in fact the format of the music file is a bottleneck. Let's see how it works. The analog output of Topping D10s was digitized by E1DA Cosmos ADC, the files from previous examples were used to feed the Topping DAC. ADC sampling was 96kHz/24bit, bandwidth of SINAD evaluation was 22kHz.

First, let's see what we get when the DAC – ADC chain is supplied with a 44.1kHz/32bit float 1kHz sine.

system_44_32b.png


We get THD = -125 dB, SFDR of 128 dB and SINAD = 110.7 dB. This is enough to handle 16 bit test signals. This was shown only as a comparison, this is NOT a 16 bit signal.

We start measurements with 1kHz undithered sine in 44.1kHz/16 bits

system_44_16b_undithered.png


We get THD = -101.5 dB, SFDR of 106 dB, SINAD = 97 dB. So we are at almost same numbers as for the test signal itself.

Next is TPD dithered 1kHz sine

system_44_16b_dithered.png


We get THD = -123.2 dB, SFDR of 128 dB and SINAD = 96.6 dB. Compared to a signal itself, we get slightly worse THD and SFDR but slightly better SINAD (of 3.3 dB), probably a result of oversampling?

The last one is noise shape dithered 1kHz sine

system_44_16b_shaped.png


We get THD = -103.9 dB, SFDR of 103 dB and SINAD = 75 dB. Again slightly better SINAD.

And the all-in-one plot for the DAC – ADC chain

system_44_16b_allinone.png


3. Conclusion

Regardless the highest achieved SINAD of the DAC, it is the music file format that will define the theoretical maximum SINAD of our audio chain and worse, it is the background noise of the recording session and microphone path noise that in fact define the SINAD, not speaking about speakers and listening room. As a matter of fact, well engineered CD player is indistinguishable from the best SOTA DACs.
 
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mhardy6647

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To me, this topic illustrates the challenge(s) of selecting good surrogate markers in a real world that is very complicated.
One of the corollaries of choosing a surrogate marker* is could be that over-devotion to the surrogate vs. reality can result in generation of products that (for lack of a better term) teach to the test. The VW Diesel emissions debacle, I would suggest, is an example. albeit an extreme and criminally devious one!

Massachusetts state schools in the 1990s began a standardized testing program (MCAS) required for all students in the Commonwealth. A certain score was required for students to graduate from secondary school. Incentives ($) were provide to school systems that showed high levels of improvement from year over year (e.g., from really bad to pretty bad, in some cases). In the first years of the program, the best systems had, it could be argued, no where to go but down. After just a few years, many systems (and, anecdotally, perhaps mostly middle of the pack systems) altered their curricula to teach to the MCAS test -- performance to the surrogate marker becoming the end in itself. I don't think that cleavage to a surrogate marker of performance, in the MCAS case, benefited the students of the Commonwealth, on average and in the long term.

I reckon ;) that surrogate markers often result in this type of unanticipated consequence. It was, e.g., not an uncommon 'effect' in the pharmaceutical industry in the late 1990s/early 20th Century (again, and admittedly, anecdotally).

Is SINAD such a surrogate? I don't know. It depends on whether any qualitative or quantitative harm is done to the real-world peformance of a (hypothetical) component that was designed with over-attention to the surrogate.

Mind you, I am just musing here. :)_
Note my careful weasel-wording here and there!

________________
*Especially a single-number surrogate -- to say nothing of a dimensionless one (ratio)! ;)
 

DonH56

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Agreed.

Aside: achieving theoretical (~9N) SFDR requires (relatively) prime relationship between signal frequency and sampling rate. That is used in testing (see e.g. IEEE STD 1241) but rarely happens in the real world, leading to correlated quantization noise spurs as shown in the plots.

My issues have always been (1) the dynamic range of actual recorded music is typically an order of magnitude, if not several orders of magnitude, less than what our equipment can produce and (2) how much distortion we can actually hear. I do not have data on (1); anecdotally 60~80 dB seems to be pretty common. As for (2), even with a simple two-tone test I find it difficult to resolve 0.1% (-60 dB) distortion.
 

Lambda

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Regardless the highest achieved SINAD of the DAC, it is the music file format that will define the theoretical maximum SINAD of our audio chain
Assuming its only 16bit 44khz
With higer sample rates noise shaping can be way outside the audible band.

THD+N from a DAC alone is only a hint about how careful/skillfull they have engineered it.
"Everyone" can make a dac with SINAD of ~100dB by using an Ti chip and copying the reference application.

But to get over 120dB is a engineering challenge.

it is the background noise of the recording session and microphone path noise that in fact define the SINAD

If it is not completely synthesized music
 

Sokel

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Agreed.

Aside: achieving theoretical (~9N) SFDR requires (relatively) prime relationship between signal frequency and sampling rate. That is used in testing (see e.g. IEEE STD 1241) but rarely happens in the real world, leading to correlated quantization noise spurs as shown in the plots.

My issues have always been (1) the dynamic range of actual recorded music is typically an order of magnitude, if not several orders of magnitude, less than what our equipment can produce and (2) how much distortion we can actually hear. I do not have data on (1); anecdotally 60~80 dB seems to be pretty common. As for (2), even with a simple two-tone test I find it difficult to resolve 0.1% (-60 dB) distortion.
Comparing your reply with the OP's conclusion,may I ask a blasphemous question?
If the result is what we suspect it is can someone somehow benefit by masking all this,with nice distortion for example (like tubes or similar)?
 

Vacceo

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I´m not sure the comparison to standarized testing is really valid. The problem you point out with standarized testing of students is the test becoming a requirement for something else (access to university, grants...), but the idea behind the test is checking if the student possesses certain skills and knowledge.

The downside of what you show is that concentrating on the specific requirements of the test effetively allows the students to get a good number on them, but does not necessarily imply that the student has a broader knowledge or skill, just the very specific part of those required for the test. Let´s put and example with an area I know well: History. Being able to recite the calibers of guns employed in the Battle of the Marne is not knowing history, only very specific data about a very particular event disregarding the causes, consequences and influences operating in said event.

But I´m not sure that is also true on an electronic device. We are talking about devices whose task is taking a signal, processing, amplifiying it and sending to other devices that turn it into mechanical waves (sound). Among the functions of the device it is possible that we consider how the device changes the signal to accomodate to response (equalization), how effeciently does it, to what levels of power does it, but the core of the task is how much does it alteer the original signal without human interference. What else should be considered on the device?
 

DonH56

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Comparing your reply with the OP's conclusion,may I ask a blasphemous question?
If the result is what we suspect it is can someone somehow benefit by masking all this,with nice distortion for example (like tubes or similar)?
I do not know what you mean by "all this"? The quantization noise, and the distortion from most of today's components, is inaudible below clipping. Intentionally adding distortion has been debated quite a bit but I am not competent to speak to that. Studies from CRC (Toole) and others have shown listeners prefer no distortion, but there are those who claim small levels of low-order distortion is pleasing. Above my pay grade. ;)
 

Vacceo

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I do not know what you mean by "all this"? The quantization noise, and the distortion from most of today's components, is inaudible below clipping. Intentionally adding distortion has been debated quite a bit but I am not competent to speak to that. Studies from CRC (Toole) and others have shown listeners prefer no distortion, but there are those who claim small levels of low-order distortion is pleasing. Above my pay grade. ;)
Anyone that likes rock in any variant probably likes distortion, so we can leave it to the artist and the source itself.
 

REK2575

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After just a few years, many systems (and, anecdotally, perhaps mostly middle of the pack systems) altered their curricula to teach to the MCAS test -- performance to the surrogate marker becoming the end in itself. I don't think that cleavage to a surrogate marker of performance, in the MCAS case, benefited the students of the Commonwealth, on average and in the long term.

Perhaps this resonates with me as a longtime resident of 'the Commonwealth' myself ;) but I think this is an intriguing comparison. Frankly, I have little doubt anymore that companies like Topping are indeed 'teaching to the test' -- or rather, designing their products to the test, in this case one called SINAD rather than MCAS. The Topping PA5 is case in point. Designed entirely to get an excellent score on the SINAD test, which it passed with flying colors. Problem is, the product is junk otherwise; Topping knows it's defective and yet continues to sell it, and ASR continues to hawk it with the unconditionally glowing review Amir published. But hey, it aced that test! It may only last you a month before it breaks, but there's no arguing with SINAD! (If all you care about is SINAD, and not other important things, like build quality and reliability...)
 

abdo123

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Distortion has been a none-issue for the last 30 years but I still don't want to hear hiss when the track is over.

I appreciate the 1KHz FFT that Amir shares because i can look at the distortion products and deduce whether SINAD is noise or distortion limited in seconds and I can tell whether it passes my noise thresholds in a very short time.
 

Vacceo

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Perhaps this resonates with me as a longtime resident of 'the Commonwealth' myself ;) but I think this is an intriguing comparison. Frankly, I have little doubt anymore that companies like Topping are indeed 'teaching to the test' -- or rather, designing their products to the test, in this case one called SINAD rather than MCAS. The Topping PA5 is case in point. Designed entirely to get an excellent score on the SINAD test, which it passed with flying colors. Problem is, the product is junk otherwise; Topping knows it's defective and yet continues to sell it, and ASR continues to hawk it with the unconditionally glowing review Amir published. But hey, it aced that test! It may only last you a month before it breaks, but there's no arguing with SINAD! (If all you care about is SINAD, and not other important things, like build quality and reliability...)
Why so? Due to durability? Due to handling?
 

REK2575

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Failure rate of the PA5 is unacceptably high. Topping has acknowledged there is a problem, but have done nothing about it.
 

IPunchCholla

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Failure rate of the PA5 is unacceptably high. Topping has acknowledged there is a problem, but have done nothing about it.
Well, to be fair, Topping is apparently leaning on the shady retailers who weren’t honoring warranty claims. The also said they are making a change to manufacturing that will fix the issue. As long as they aren’t lying, that seems like doing something.

I said this as an owner with a PA5 that has not had any issues. Since I haven’t had an issue with the amp, and it drives my big three ways with plenty of oomph and it sounds totally clean right up to clipping and that it cost $350 from a US retailer that put an extra year of warranty on it, am I supposed to be angry at Topping for playing the SINAD game?
 

Tangband

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God of SINAD vs. reality we get from most available music files

There is a good thread here in ASR discussing the practical importance of SINAD number

which links to the original article at

Let me quote from that article:

“SINAD is short for “Signal to Noise And Distortion”. It’s the ratio between the signal - the stuff we want to hear, like the music we play - to all the other things we don’t want in the sound. It’s also sometimes expressed as THD+N, or “total harmonic distortion plus noise”, which is the ratio of the noise and distortion to the signal - the same thing the other way around.
As the name suggests, SINAD is a sum of two broad groups of things we don’t want in the sound: Noise, and distortion. Noise is just what it sounds like: noises leaking into your music, which can range from the “hum” of your AC power, to the “hiss” of white noise. There are a lot of potential sources of noise out there, and they can distract from what you actually want to listen to, particularly if you’re listening quietly.
Distortion, the other part, is similar to noise in that it’s an addition to your music. Unlike noise, however, distortion is produced by your music interacting with the flaws of the system. This means that distortion will be related in level to the signal causing it, whereas - as anyone who’s heard hiss on their IEMs will know - noise can be loud without anything playing at all.
This is the big trouble with SINAD: In some cases, a low score points to an amplifier or DAC that is just plain not working, but in others, it’s only catching “problems” that you won’t actually be able to hear.”


Obviously, the SINAD, or THD+N, which is absolutely same thing just with opposite sign, is not well understood or simply not understood in general public, as we can see from many threads here in ASR. Let me name a few:




SINAD is appealing for both inexperienced readers and technically oriented reviewers as it gives a single number that is used in simplified charts as a comparative measure of various audio products. As any simplification, there is a question if such simplification is good enough to be a basis of comparisons of audio products. It definitely tells something, but how would it be useful in a real life?

Let's thing, for a while, about music files that we use to feed our beloved audio chains. Streaming services yield files of unknown quality, regardless label like “lossless”, “hires” etc. File analysis often shows that such label is incorrect. In fact, well prepared “old style” 44.1kHz/16bit files are still a very good source of music and many so-called “hires” files and streams are just a re-sampled versions of original 44.1/16 versions. The other point to be mentioned is that a background noise during recording and microphone path noise are barely that low to utilize dynamic range of the 44.1/16 format. In fact, the best recordings only attack only 60dB range, and this is for classical music.

View attachment 222728

Popular music often sticks with something like 20dB range. So, there is a question, what SINAD we can get from 44.1kHz/16bit files, just in theory? And after processing by a DAC?

1. Analysis of 44.1kHz/16bit files with respect to achievable SINAD

SNR of 16bit full scale sine wave to the rms value of quantization noise in theory is:
SNR = 6.02N + 1.76dB

For N = 16 (bits) we get SNR = 98.08 dB, theoretical maximum

With 1kHz undithered sine in 44.1kHz/16 bits we measure

View attachment 222718

This makes SINAD = 97 dB, THD = -101 dB, but SFDR (spurious free dynamic range) is suffering at some 104 dB due to quantization noise and this quantization noise becomes audible at low level signals like -60 dBFS.

To get rid of spurious frequency components of quantization noise we add a small amount of noise called dither. Frequency independent TPD dither makes a good job of reducing THD, increasing SFDR at the expense of about 4.8dB loss of SNR. Spectrum of 1kHz TPD dithered 44.1kHz/16bit sine looks like this:

View attachment 222719

We get THD = -126.7 dB, SFDR of some 132 dB and SINAD = 93.3 dB.

There are attempts to use dither methods that are not frequency independent. They are based on assumption that noise is most audible in certain frequency range, so they reduce noise rms level below some 12 kHz at the expense of fast rise in noise energy between 12 kHz and 20 kHz. We call this noise shaping and the spectrum of 1kHz sine wave with noise shaped dither in 44.1kHz/16bit format looks typically like this:

View attachment 222720

We get THD = -104.1 dB, but SFDR of 102 dB and SINAD only 70.7 dB, measured over 22 kHz bandwidth without frequency weighting. Noise shaping is responsible for this huge SINAD loss and the reason is we have only 44.1kHz sampling, i.e. 22.05 kHz BW. Noise shaping would be more effective only at higher sampling rates like 96 kHz.

There might be an idea of resampling the 44.1kHz/16bit source file to higher sampling rate and using noise shaping, but once we have a 44.1kHz/16bit original file, a little to improve SNR or SINAD can be done, resulting only in one or few dB difference. No DAC with 130 dB SINAD would make any miracle here.

As a comparison, next plot shows all the previously discussed files – undithered, TPD dithered and noise shaped 1kHz sine in 44.1kHz/16bit format in one graph.

View attachment 222721


2. 1kHz sine waves in 44.1/16 format played through through an oversampling DAC, Topping D10s

Audiophiles, supported by popular audio reviewers, often assume that playing “low resolution” 44.1/16 format files through some miraculous oversampling DAC that oversamples at 384kHz/32bit will get something more from 44.1/16 files. Unfortunately, not really. We may get some tiny improvement in some cases, but in fact the format of the music file is a bottleneck. Let's see how it works. The analog output of Topping D10s was digitized by E1DA Cosmos ADC, the files from previous examples were used to feed the Topping DAC. ADC sampling was 96kHz/24bit, bandwidth of SINAD evaluation was 22kHz.

First, let's see what we get when the DAC – ADC chain is supplied with a 44.1kHz/32bit float 1kHz sine.

View attachment 222722

We get THD = -125 dB, SFDR of 128 dB and SINAD = 110.7 dB. This is enough to handle 16 bit test signals. This was shown only as a comparison, this is NOT a 16 bit signal.

We start measurements with 1kHz undithered sine in 44.1kHz/16 bits

View attachment 222723

We get THD = -101.5 dB, SFDR of 106 dB, SINAD = 97 dB. So we are at almost same numbers as for the test signal itself.

Next is TPD dithered 1kHz sine

View attachment 222724

We get THD = -123.2 dB, SFDR of 128 dB and SINAD = 96.6 dB. Compared to a signal itself, we get slightly worse THD and SFDR but slightly better SINAD (of 3.3 dB), probably a result of oversampling?

The last one is noise shape dithered 1kHz sine

View attachment 222725

We get THD = -103.9 dB, SFDR of 103 dB and SINAD = 75 dB. Again slightly better SINAD.

And the all-in-one plot for the DAC – ADC chain

View attachment 222726

3. Conclusion

Regardless the highest achieved SINAD of the DAC, it is the music file format that will define the theoretical maximum SINAD of our audio chain and worse, it is the background noise of the recording session and microphone path noise that in fact define the SINAD, not speaking about speakers and listening room. As a matter of fact, well engineered CD player is indistinguishable from the best SOTA DACs.
Interesting.:),

From the recording perspective , with its analog nature ,- the many microphones and mic. amplifiers used has a SINAD about 80-100 dB at best.

When recording , one has to have some headroom in the recording session to avoid clipping , - this means loosing 2 bits in the A/D just for safety reasons, if its a live recording. You always do the recording with more than - 10 dB marginal from 0 .

Most AD converters with 10 years of age or more have a SINAD less than 95 dB.

Then we have digital mixerboards with maybe 18 bit real resolution at best , the plug in effects used in the DAW thats no better than 16 bit in real life ( reverbs, eq, compressors and much more ) . Digital volume controls and normalisation processes makes it even worse.

All this ads to be a finished recording material of maybe 80 dB SINAD when you play it trough your new dac with a SINAD of 115 dB.

Still, I can sometimes hear SRC artefacts from some DAWs and from some players like yamaha wxc50. Strange, Isnt it ?

However : There is no reason at 2022 to make dacs with worse SINAD than - 110 dB, - it costs nothing these days.

( If every chain in the recording had a SINAD of about 70 dB , as it was in 1960-1970 , the finished result on the vinyl record would have a SINAD of maybe 50 dB and could still be regarded as ”good sounding”. )

Edit: With that said, I dont like 320 kbit mp3 or bluetooth because theres no excuse not to use lossless at 2022, Amirm has a point here.
 
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amirm

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3. Conclusion

Regardless the highest achieved SINAD of the DAC, it is the music file format that will define the theoretical maximum SINAD of our audio chain and worse, it is the background noise of the recording session and microphone path noise that in fact define the SINAD, not speaking about speakers and listening room. As a matter of fact, well engineered CD player is indistinguishable from the best SOTA DACs.
These are wrong conclusions. I will list a few reasons but I highly suggest that you read research performed into channel transparency we need for audio (Fielder, Stuart, et. al.)

1. Noise is additive. For a device to not cost you more than 0.5 dB of SINAD, it needs to have a SINAD that is 10 dB higher than your content. So even if you arrive at 93 dB being SINAD of 16 bit music, your hardware needs to have a SINAD of 103 dB. Even then, your effective SINAD will now be 92.5.

2. In higher SINAD tier, the metric is dominated usually by noise, not distortion. Digitally created/mixed music can have infinite dynamic range. Start with total digital silence and then the rest will create divide by zero meaning you can have any SINAD (SNR) you want. It only becomes limited by how loud you play and equipment noise.

3. Many people including myself play > 16 bit content. MQA research in process of encoding millions of tracks for their format shows that the best case dynamic range is about 18 bits, not 16 as you assume. And this is analyzing real content/music.

4. It costs nothing to get higher SINAD than 96 dB. State of the art DACS in 115 dB range exists for peanuts. Why on earth would you argue that people should opt for less?

5. Sensitive IEM users can most definitely hear minute amounts of noise. My 50 mv graph shows that only a few high SINAD devices are capable of providing totally silent background when music is not playing (> 90 to 92 dB).

6. DSP processing such as EQ can reduce effective dynamic range of devices like headphone amplifiers to allow for overflows. So while you may start with 100 dB, you may easily wind up with 90 dB effective if the boost is high. In-room EQ systems like Dirac do this to routinely by pulling all the peaks way down to flatten the response. Not only do you lose dynamic range, but also push a lot of the low order bits into silence or sub bit in 16 bit format.

7. There is no such thing as single number noise SPL for microphones, rooms, etc. Such noise highly varies with frequency so any simplified statement about them is wrong. Again, read peer reviewed research papers from Fielder and Stuart. Or watch my video on the same:

8. Please don't quote other uninformed/non-practicing opinions of people regarding audibility of distortion. This type of work requires listener training to represent all listeners. Using casual groups of people, as sadly done in some research, just produces wrong results. Witness how the masses are oblivious to compression artifacts whereas trained listeners can easily hear them.

9. The notion that you can pick any device ("CD player") you want and it would be transparent is just wrong. You need to measure to make sure this transparency is there. There are a ton of devices in the red category of my SINAD ratings which fall below your criteria:
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Really folks. Go do something else with your time. Fighting SINAD is like fighting with a restaurant to not have clean dishes. It is not like your food would be cheaper if they served your food on dirty ones.
 
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