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
www.audiosciencereview.com
which links to the original article at
www.headphones.com
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:
www.audiosciencereview.com
www.audiosciencereview.com
www.audiosciencereview.com
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.
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
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:
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:
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.
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.
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
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
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
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
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.
There is a good thread here in ASR discussing the practical importance of SINAD number
Could we all be wrong about SINAD?
Hi I’ve noticed that my NAD C658, which measure like cr@p, sounded much better than the Denon X4700H, which I’ve recently auditioned at my home, before and after running Audyssey. Another example is the PS Audio Directstream DAC, which also scored terribly on ASR, and yet, most audiophiles...
www.audiosciencereview.com
Evaluating SINAD - Why it's NOT important
Blaine Lacross and Andrew Park examine SINAD, a popular index commonly used to evaluate amps and DACs. In this article, they explain why it's not important
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:
How much SINAD is enough
So been getting upgrade envy lately with some of the latest products returning amazing results - but it had me wondering is it worth it - is there a baseline acceptable performance a product should meet and anything else is just chasing numbers ? Two things : 1) the sound from my average...
www.audiosciencereview.com
Focus on SINAD Gives Vendors Hiding Space
I brought this up in an earlier thread but wanted to raise up to start a conversation on it. I still wonder what all the focus on SINAD and THD/noise comes to? The measurements are very appreciated and great for filtering out complete junk, but reasonable vendors are now chasing meaninglessly...
www.audiosciencereview.com
Can we compare SINAD between a SACD/CD player and a DAC?
I am using a SACD Yamaha CD-S2100. Released 5 years ago, the measurements were considered quite good. - Signal to noise ratio: 116 db - Distorsion: 0.002% This seems to give a SINAD of 94 db. Not really exiting... Am I wrong? Dominique
www.audiosciencereview.com
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.
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
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:
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:
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.
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.
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
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
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
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
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.
Last edited:
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).
