Do we need 24/96K USB interface ?
- Thread starter kaushik
- Start date
Audiodoc
Well-Known Member
If one has a big collection of 24 bit audio then yes. The other way round is to use spdif or toslisk. For 16 bit songs hardly matters
It is just a copy from different forum. But, i liked this analogy. So pasting it here..
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Posted by gregorio in head-fi.org on 19/03/2009
It seems to me that there is a lot of misunderstanding regarding what bit depth is and how it works in digital audio. This misunderstanding exists not only in the consumer and audiophile worlds but also in some education establishments and even some professionals. This misunderstanding comes from supposition of how digital audio works rather than how it actually works. It's easy to see in a photograph the difference between a low bit depth image and one with a higher bit depth, so it's logical to suppose that higher bit depths in audio also means better quality. This supposition is further enforced by the fact that the term 'resolution' is often applied to bit depth and obviously more resolution means higher quality. So 24bit is Hi-Rez audio and 24bit contains more data, therefore higher resolution and better quality. All completely logical supposition but I'm afraid this supposition is not entirely in line with the actual facts of how digital audio works. I'll try to explain:
When recording, an Analogue to Digital Converter (ADC) reads the incoming analogue waveform and measures it so many times a second (1*). In the case of CD there are 44,100 measurements made per second (the sampling frequency). These measurements are stored in the digital domain in the form of computer bits. The more bits we use, the more accurately we can measure the analogue waveform. This is because each bit can only store two values (0 or 1), to get more values we do the same with bits as we do in normal counting. IE. Once we get to 9, we have to add another column (the tens column) and we can keep adding columns add infinitum for 100s, 1000s, 10000s, etc. The exact same is true for bits but because we only have two values per bit (rather than 10) we need more columns, each column (or additional bit) doubles the number of vaules we have available. IE. 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024 .... If these numbers appear a little familiar it is because all computer technology is based on bits so these numbers crop up all over the place. In the case of 16bit we have roughly 65,000 different values available. The problem is that an analogue waveform is constantly varying. No matter how many times a second we measure the waveform or how many bits we use to store the measurement, there are always going to be errors. These errors in quantifying the value of a constantly changing waveform are called quantisation errors. Quantisation errors are bad, they cause distortion in the waveform when we convert back to analogue and listen to it.
So far so good, what I've said until now would agree with the supposition of how digital audio works. I seem to have agreed that more bits = higher resolution. True, however, where the facts start to diverge from the supposition is in understanding the result of this higher resolution. Going back to what I said above, each time we increase the bit depth by one bit, we double the number of values we have available (EG. 4bit = 16 values, 5bit = 32 values). If we double the number of values, we halve the amount of quantisation errors. Still with me? Because now we come to the whole nub of the matter. There is in fact a perfect solution to quantisation errors which completely (100%) eliminates quantisation distortion, the process is called 'Dither' and is built into every ADC on the market.
Dither: Essentially during the conversion process a very small amount of white noise is added to the signal, this has the effect of completely randomising the quantisation errors. Randomisation in digital audio, once converted back to analogue is heard as pure white (un-correlated) noise. The result is that we have an absolutely perfect measurement of the waveform (2*) plus some noise. In other words, by dithering, all the measurement errors have been converted to noise. (3*).
Hopefully you're still with me, because we can now go on to precisely what happens with bit depth. Going back to the above, when we add a 'bit' of data we double the number of values available and therefore halve the number of quantisation errors. If we halve the number of quantisation errors, the result (after dithering) is a perfect waveform with halve the amount of noise. To phrase this using audio terminology, each extra bit of data moves the noise floor down by 6dB (half). We can turn this around and say that each bit of data provides 6dB of dynamic range (*4). Therefore 16bit x 6db = 96dB. This 96dB figure defines the dynamic range of CD. (24bit x 6dB = 144dB).
So, 24bit does add more 'resolution' compared to 16bit but this added resolution doesn't mean higher quality, it just means we can encode a larger dynamic range. This is the misunderstanding made by many. There are no extra magical properties, nothing which the science does not understand or cannot measure. The only difference between 16bit and 24bit is 48dB of dynamic range (8bits x 6dB = 48dB) and nothing else. This is not a question for interpretation or opinion, it is the provable, undisputed logical mathematics which underpins the very existence of digital audio.
So, can you actually hear any benefits of the larger (48dB) dynamic range offered by 24bit? Unfortunately, no you can't. The entire dynamic range of some types of music is sometimes less than 12dB. The recordings with the largest dynamic range tend to be symphony orchestra recordings but even these virtually never have a dynamic range greater than about 60dB. All of these are well inside the 96dB range of the humble CD. What is more, modern dithering techniques (see 3 below), perceptually enhance the dynamic range of CD by moving the quantisation noise out of the frequency band where our hearing is most sensitive. This gives a percievable dynamic range for CD up to 120dB (150dB in certain frequency bands).
You have to realise that when playing back a CD, the amplifier is usually set so that the quietest sounds on the CD can just be heard above the noise floor of the listening environment (sitting room or cans). So if the average noise floor for a sitting room is say 50dB (or 30dB for cans) then the dynamic range of the CD starts at this point and is capable of 96dB (at least) above the room noise floor. If the full dynamic range of a CD was actually used (on top of the noise floor), the home listener (if they had the equipment) would almost certainly cause themselves severe pain and permanent hearing damage. If this is the case with CD, what about 24bit Hi-Rez. If we were to use the full dynamic range of 24bit and a listener had the equipment to reproduce it all, there is a fair chance, depending on age and general health, that the listener would die instantly. The most fit would probably just go into coma for a few weeks and wake up totally deaf. I'm not joking or exaggerating here, think about it, 144dB + say 50dB for the room's noise floor. But 180dB is the figure often quoted for sound pressure levels powerful enough to kill and some people have been killed by 160dB. However, this is unlikely to happen in the real world as no DACs on the market can output the 144dB dynamic range of 24bit (so they are not true 24bit converters), almost no one has a speaker system capable of 144dB dynamic range and as said before, around 60dB is the most dynamic range you will find on a commercial recording.
So, if you accept the facts, why does 24bit audio even exist, what's the point of it? There are some useful application for 24bit when recording and mixing music. In fact, when mixing it's pretty much the norm now to use 48bit resolution. The reason it's useful is due to summing artefacts, multiple processing in series and mainly headroom. In other words, 24bit is very useful when recording and mixing but pointless for playback. Remember, even a recording with 60dB dynamic range is only using 10bits of data, the other 6bits on a CD are just noise. So, the difference in the real world between 16bit and 24bit is an extra 8bits of noise.
I know that some people are going to say this is all rubbish, and that I can easily hear the difference between a 16bit commercial recording and a 24bit Hi-Rez version. Unfortunately, you can't, it's not that you don't have the equipment or the ears, it is not humanly possible in theory or in practice under any conditions!! Not unless you can tell the difference between white noise and white noise that is well below the noise floor of your listening environment!! If you play a 24bit recording and then the same recording in 16bit and notice a difference, it is either because something has been 'done' to the 16bit recording, some inappropriate processing used or you are hearing a difference because you expect a difference.
G
1 = Actually these days the process of AD conversion is a little more complex, using oversampling (very high sampling frequencies) and only a handful of bits. Later in the conversion process this initial sampling is 'decimated' back to the required bit depth and sample rate.
2 = The concept of the perfect measurement or of recreating a waveform perfectly may seem like marketing hype. However, in this case it is not. It is in fact the fundamental tenet of the Nyquist-Shannon Sampling Theorem on which the very existence and invention of digital audio is based. From WIKI: In essence the theorem shows that an analog signal that has been sampled can be perfectly reconstructed from the samples. I know there will be some who will disagree with this idea, unfortunately, disagreement is NOT an option. This theorem hasn't been invented to explain how digital audio works, it's the other way around. Digital Audio was invented from the theorem, if you don't believe the theorem then you can't believe in digital audio either!!
3 = In actual fact these days there are a number of different types of dither used during the creation of a music product. Most are still based on the original TPDFs (triangular probability density function) but some are a little more 'intelligent' and re-distribute the resulting noise to less noticeable areas of the hearing spectrum. This is called noise-shaped dither.
4 = Dynamic range, is the range of volume between the noise floor and the maximum volume.
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Posted by gregorio in head-fi.org on 19/03/2009
It seems to me that there is a lot of misunderstanding regarding what bit depth is and how it works in digital audio. This misunderstanding exists not only in the consumer and audiophile worlds but also in some education establishments and even some professionals. This misunderstanding comes from supposition of how digital audio works rather than how it actually works. It's easy to see in a photograph the difference between a low bit depth image and one with a higher bit depth, so it's logical to suppose that higher bit depths in audio also means better quality. This supposition is further enforced by the fact that the term 'resolution' is often applied to bit depth and obviously more resolution means higher quality. So 24bit is Hi-Rez audio and 24bit contains more data, therefore higher resolution and better quality. All completely logical supposition but I'm afraid this supposition is not entirely in line with the actual facts of how digital audio works. I'll try to explain:
When recording, an Analogue to Digital Converter (ADC) reads the incoming analogue waveform and measures it so many times a second (1*). In the case of CD there are 44,100 measurements made per second (the sampling frequency). These measurements are stored in the digital domain in the form of computer bits. The more bits we use, the more accurately we can measure the analogue waveform. This is because each bit can only store two values (0 or 1), to get more values we do the same with bits as we do in normal counting. IE. Once we get to 9, we have to add another column (the tens column) and we can keep adding columns add infinitum for 100s, 1000s, 10000s, etc. The exact same is true for bits but because we only have two values per bit (rather than 10) we need more columns, each column (or additional bit) doubles the number of vaules we have available. IE. 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024 .... If these numbers appear a little familiar it is because all computer technology is based on bits so these numbers crop up all over the place. In the case of 16bit we have roughly 65,000 different values available. The problem is that an analogue waveform is constantly varying. No matter how many times a second we measure the waveform or how many bits we use to store the measurement, there are always going to be errors. These errors in quantifying the value of a constantly changing waveform are called quantisation errors. Quantisation errors are bad, they cause distortion in the waveform when we convert back to analogue and listen to it.
So far so good, what I've said until now would agree with the supposition of how digital audio works. I seem to have agreed that more bits = higher resolution. True, however, where the facts start to diverge from the supposition is in understanding the result of this higher resolution. Going back to what I said above, each time we increase the bit depth by one bit, we double the number of values we have available (EG. 4bit = 16 values, 5bit = 32 values). If we double the number of values, we halve the amount of quantisation errors. Still with me? Because now we come to the whole nub of the matter. There is in fact a perfect solution to quantisation errors which completely (100%) eliminates quantisation distortion, the process is called 'Dither' and is built into every ADC on the market.
Dither: Essentially during the conversion process a very small amount of white noise is added to the signal, this has the effect of completely randomising the quantisation errors. Randomisation in digital audio, once converted back to analogue is heard as pure white (un-correlated) noise. The result is that we have an absolutely perfect measurement of the waveform (2*) plus some noise. In other words, by dithering, all the measurement errors have been converted to noise. (3*).
Hopefully you're still with me, because we can now go on to precisely what happens with bit depth. Going back to the above, when we add a 'bit' of data we double the number of values available and therefore halve the number of quantisation errors. If we halve the number of quantisation errors, the result (after dithering) is a perfect waveform with halve the amount of noise. To phrase this using audio terminology, each extra bit of data moves the noise floor down by 6dB (half). We can turn this around and say that each bit of data provides 6dB of dynamic range (*4). Therefore 16bit x 6db = 96dB. This 96dB figure defines the dynamic range of CD. (24bit x 6dB = 144dB).
So, 24bit does add more 'resolution' compared to 16bit but this added resolution doesn't mean higher quality, it just means we can encode a larger dynamic range. This is the misunderstanding made by many. There are no extra magical properties, nothing which the science does not understand or cannot measure. The only difference between 16bit and 24bit is 48dB of dynamic range (8bits x 6dB = 48dB) and nothing else. This is not a question for interpretation or opinion, it is the provable, undisputed logical mathematics which underpins the very existence of digital audio.
So, can you actually hear any benefits of the larger (48dB) dynamic range offered by 24bit? Unfortunately, no you can't. The entire dynamic range of some types of music is sometimes less than 12dB. The recordings with the largest dynamic range tend to be symphony orchestra recordings but even these virtually never have a dynamic range greater than about 60dB. All of these are well inside the 96dB range of the humble CD. What is more, modern dithering techniques (see 3 below), perceptually enhance the dynamic range of CD by moving the quantisation noise out of the frequency band where our hearing is most sensitive. This gives a percievable dynamic range for CD up to 120dB (150dB in certain frequency bands).
You have to realise that when playing back a CD, the amplifier is usually set so that the quietest sounds on the CD can just be heard above the noise floor of the listening environment (sitting room or cans). So if the average noise floor for a sitting room is say 50dB (or 30dB for cans) then the dynamic range of the CD starts at this point and is capable of 96dB (at least) above the room noise floor. If the full dynamic range of a CD was actually used (on top of the noise floor), the home listener (if they had the equipment) would almost certainly cause themselves severe pain and permanent hearing damage. If this is the case with CD, what about 24bit Hi-Rez. If we were to use the full dynamic range of 24bit and a listener had the equipment to reproduce it all, there is a fair chance, depending on age and general health, that the listener would die instantly. The most fit would probably just go into coma for a few weeks and wake up totally deaf. I'm not joking or exaggerating here, think about it, 144dB + say 50dB for the room's noise floor. But 180dB is the figure often quoted for sound pressure levels powerful enough to kill and some people have been killed by 160dB. However, this is unlikely to happen in the real world as no DACs on the market can output the 144dB dynamic range of 24bit (so they are not true 24bit converters), almost no one has a speaker system capable of 144dB dynamic range and as said before, around 60dB is the most dynamic range you will find on a commercial recording.
So, if you accept the facts, why does 24bit audio even exist, what's the point of it? There are some useful application for 24bit when recording and mixing music. In fact, when mixing it's pretty much the norm now to use 48bit resolution. The reason it's useful is due to summing artefacts, multiple processing in series and mainly headroom. In other words, 24bit is very useful when recording and mixing but pointless for playback. Remember, even a recording with 60dB dynamic range is only using 10bits of data, the other 6bits on a CD are just noise. So, the difference in the real world between 16bit and 24bit is an extra 8bits of noise.
I know that some people are going to say this is all rubbish, and that I can easily hear the difference between a 16bit commercial recording and a 24bit Hi-Rez version. Unfortunately, you can't, it's not that you don't have the equipment or the ears, it is not humanly possible in theory or in practice under any conditions!! Not unless you can tell the difference between white noise and white noise that is well below the noise floor of your listening environment!! If you play a 24bit recording and then the same recording in 16bit and notice a difference, it is either because something has been 'done' to the 16bit recording, some inappropriate processing used or you are hearing a difference because you expect a difference.
G
1 = Actually these days the process of AD conversion is a little more complex, using oversampling (very high sampling frequencies) and only a handful of bits. Later in the conversion process this initial sampling is 'decimated' back to the required bit depth and sample rate.
2 = The concept of the perfect measurement or of recreating a waveform perfectly may seem like marketing hype. However, in this case it is not. It is in fact the fundamental tenet of the Nyquist-Shannon Sampling Theorem on which the very existence and invention of digital audio is based. From WIKI: In essence the theorem shows that an analog signal that has been sampled can be perfectly reconstructed from the samples. I know there will be some who will disagree with this idea, unfortunately, disagreement is NOT an option. This theorem hasn't been invented to explain how digital audio works, it's the other way around. Digital Audio was invented from the theorem, if you don't believe the theorem then you can't believe in digital audio either!!
3 = In actual fact these days there are a number of different types of dither used during the creation of a music product. Most are still based on the original TPDFs (triangular probability density function) but some are a little more 'intelligent' and re-distribute the resulting noise to less noticeable areas of the hearing spectrum. This is called noise-shaped dither.
4 = Dynamic range, is the range of volume between the noise floor and the maximum volume.
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Thad E Ginathom
Well-Known Member
Here is an article from Sound On Sound that explains some of these things very well
Digital Problems, Practical Solutions
The best thing about this article is that there are actual sound sample files, although the link to them is a little hard to spot. Look for the box, Audio Examples. The theory is brought to life by these examples.
What can we hear? Another article with useful actual sound examples:
Ethan Winner: Artifact Audibility Comparisons
Digital Problems, Practical Solutions
The best thing about this article is that there are actual sound sample files, although the link to them is a little hard to spot. Look for the box, Audio Examples. The theory is brought to life by these examples.
What can we hear? Another article with useful actual sound examples:
Ethan Winner: Artifact Audibility Comparisons
I kinda speed read this article long back when I was researching on what DAC to buy, and it was somewhere in the back of my mind when I decided to spend $$$$ on a 16/44.1 DAC. Of course I did not go by the intellectual idea alone, articles like these only gave me faith that I could achieve building a musical and accurate system with 16/44.1 format. Besides that I couldn't imagine seeing Carnatic music releases in 24/192 format on the shelves in the next 5 years, where a large market audience is still on 3-in-one portable cd players.
Cheers
Cheers
These days most of the PCs / OS have 24/96 capability built-in. New Apple products are 24/192 compatible.
It is OK to have future-proof system.
If USB input on a DAC is implemented properly, you do not need USB>SPDF interface.
New DACs are able to deliver audio performance comparable to SPDF input from a USB input.
In my audio systems, upsampling (both Wadia and CA products) resulted in better audio reproduction.
Wadia also delivers good sound from their USB input.
I listen to music ranging from 16/44 to 24/192. I should also mention in my experience the higher sampling rate files reproduced better sound than lower sampling rates.
It is OK to have future-proof system.
If USB input on a DAC is implemented properly, you do not need USB>SPDF interface.
New DACs are able to deliver audio performance comparable to SPDF input from a USB input.
In my audio systems, upsampling (both Wadia and CA products) resulted in better audio reproduction.
Wadia also delivers good sound from their USB input.
I listen to music ranging from 16/44 to 24/192. I should also mention in my experience the higher sampling rate files reproduced better sound than lower sampling rates.
Considering the same master...yeah sure..24/96 "can" have theoretical and sometimes real advantages. It's just the sampling rate though; as far as music playback is concerned..you get absolutely no benefit over the 16bit redbook spec. Except maybe in situations where you want to use your PC as a preamp (software volume control).
Anything anything over 96khz is a waste in every imaginable way though..unless you have pet dolphins and bats who also want to enjoy the music with you. If you find anyone saying they can hear the difference between a 96 and 192..then
1) They're simply imagining it
2) Both files have different masters OR
3) Their hardware is doing something silly with one or all input sample rates
Having said that, 16/44.1 CD is still perfectly fine. It's just that producers have been doing a very bad job of it lately.
Anything anything over 96khz is a waste in every imaginable way though..unless you have pet dolphins and bats who also want to enjoy the music with you. If you find anyone saying they can hear the difference between a 96 and 192..then
1) They're simply imagining it
2) Both files have different masters OR
3) Their hardware is doing something silly with one or all input sample rates
Having said that, 16/44.1 CD is still perfectly fine. It's just that producers have been doing a very bad job of it lately.
Knowledge, Opinion and the Audio Experience
Please read:
Knowledge, Opinion and the Audio Experience
Please read:
Knowledge, Opinion and the Audio Experience
square_wave
Well-Known Member
I have seen this discussion at headfi and many other similar threads on forums like AA and Audiogon.
The points discussed are not completely conclusive since many factors are not really kept in the right perspective. It is mostly a theory ramble some of which are absolutely correct from an academic perspective.
The ground reality is that the same album downloaded from HD tracks (24 bit, 192 kHz) sounds better than the cd version. The difference could be due to many factors .
The points discussed are not completely conclusive since many factors are not really kept in the right perspective. It is mostly a theory ramble some of which are absolutely correct from an academic perspective.
The ground reality is that the same album downloaded from HD tracks (24 bit, 192 kHz) sounds better than the cd version. The difference could be due to many factors .
Thad E Ginathom
Well-Known Member
Cynic speaking 
...
Whoa! We just change this setting on the save-as screen and we can charge more for it!
24/192 is going to be one of the great hifi rip-offs of the future. Maybe the difference can be heard, maybe it can't. Maybe the music was originally mastered in high-definition ...and maybe it wasn't.
...Whoa! We just change this setting on the save-as screen and we can charge more for it!
24/192 is going to be one of the great hifi rip-offs of the future. Maybe the difference can be heard, maybe it can't. Maybe the music was originally mastered in high-definition ...and maybe it wasn't.
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That's not surprising at all. I have a few 24/96 albums from HDtracks and iTrax as well, which sound better than their CD counterparts. However, that's not because of any inherent flaw of the 16/44.1 redbook spec as such. These come from DSD sources, which are almost always mastered in a much more professional manner...minimal compression and better noise shaping/dithering etc.
But if you hear a difference between a 24/96 and 24/192 from the same master...then something is at fault.
There's no rocket science here. Unless one wants to hear the sounds of silence, 192 doesn't make any sense for "music playback".
Again, I must reiterate...this is all considering we're keeping the masters same. A diligently mastered 16/32 can sound better than a sloppily made 24/96.
Thad E Ginathom
Well-Known Member
That's the key point. If they then add that they are supplying it in at 96 or 192 just to make sure the most bat-like amongst us get every last whisper, even if it is impossible, then fair enough --- but otherwise, it's just going to be buying music by the gigabyte, and we might just as well buy it by the pound, or books by the meter.
Zero compression! And... I'd have to go back to the link I posted earlier and read it again, but I don't think that any dithering is necessary either.
square_wave
Well-Known Member
I more or less agree with you.
I was talking about the ground reality. I have couple of friend - audiophiles with fairly high end systems who have moved into HD tracks.
We have compared many times and the downloaded HD tracks wins hands down all the time.
Not sure why though
^^I agree, 24/96 from a DSD can sound better than CD. I was simply talking about the choice of 192. I wouldn't say "always" though. I have the Metallica(Black Album) in 24/96 from hdtracks..and I can tell you that a CBS Japanese pressing I have of it sounds much better. Don't know why..I'm guessing it comes from the DVD-A, coz Metallica never got any SACD releases iirc.
If you can get 24/96 from DSD masters..sure..go for it. There's very high probability that it sounds better than the CD you have.
@Thad--"
24/192 is going to be one of the great hifi rip-offs of the future
I would say it's already happening. Future rip-off crown probably belongs to DXD.
If you can get 24/96 from DSD masters..sure..go for it. There's very high probability that it sounds better than the CD you have.
@Thad--"
24/192 is going to be one of the great hifi rip-offs of the future
I would say it's already happening
. Future rip-off crown probably belongs to DXD.Thad E Ginathom
Well-Known Member
Yes, you are right. Articles have been posted here showing simple analysis of some so-called high-res recordings revealing that that they have been taken from CDs
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