The SuperAudio CD (SACD) explained
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| Posted by | Jan Willem |
| Posted on | 25/10/02 14:57 |
| Number of views | 19820 |
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What we talked about in the page before could be summarized as a signal, some filtering, some modulating, and we finally have sound. Since the normal human ear can hear only sounds in a frequency rate between 20Hz and 22KHz , the sampling rate of 44.1Khz should be sufficient for all "ears".
However, all this filtering costs quality! Sadly enough PCM technology requires it, but Philips and Sony found a better way to handle all this for SACD. They call it DSD. We will explain this later on. Sometimes people complain about the "too much digital" sound of music cd's. They may have a point. There's more to music and sound than you first might think of. Sound has pitch , loudness and quality. And it's that quality what makes things so interesting. We are talking about timbre and harmonics of sounds. More information about timbre and harmonics of sound waves can be found here.
These "extra" additions to the original sound wave make the sound special. They give an instrument its special sound. The more of these timbres and harmonics you can store, the better.
The SACD is capable of capturing sound up to 100kHz using sampling up to 2800kHz (2.8 MHz). You can be sure that the timbre and harmonics are of a superb quality compared to the 44.1kHz a normal audio cd can cope with. Even for the untrained ear it's a world of difference when listening to SACD compared to normal CD audio. You hear "more" sound.
This is mainly because if you use SACD to its fullest potential, you'd have six speakers for the sound. There is this statement that says if you want people to hear a nice digitalized sound , you would need at least a sampling FOUR TIMES the frequency rate of that sound or some people might hear the difference.
The improvement: DSD
DSD means Direct Stream Digital. It is a process based on 1-bit sigma-delta modulation, and operates with a sampling frequency of 2.8224 MHz (This is 64 times the 44.1 kHz used in a normal CD!). At first the technology wasn't meant for the normal consumer. The Direct Stream Digital technology was meant for the digital archiving of priceless analog master tapes , but after a while Sony and Philips decided to share the technology with the world
Remember the process for normal audio ?
1: Delta-Sigma Modulator
2: Decimation Digital Filter
3: Interpolation Digital Filter
4: Delta-Sigma Modulator
5: Analog Low Pass Filter
1 : Delta-Sigma Modulator
5 : Analog Low Pass Filter
Looks incredibly simple when compared to the standard audio CD, doesn't it ? There is no need anymore for another Delta-Sigma modulator and both the Decimation and Interpolation filter have gone ! No filters and modulation = less quality loss and much easier to explain
Not only claims Sony to have a better frequency response ; They also claim that with this technology you can hear more detail, have a much clearer sound and even the acoustic space surrounding an instrument can be heard. DSD technology tries to reproduce every nuance of the sound you were meant to hear.
Why the SACD sounds betterWant to submit your own review? Click here
Posted by Tiikeri on Friday 25 October 2002 22:26
SACD is just a pure technical crap-like solution to eternal problem - how to create sound that feels natural. And SACD won't feel nature-like any more than cd. It WON'T solve the problem, far from it. To create real 'space' to sound requires different approach, like surround planar speakers. If you've heard even the earliest planar ones (like Quad ESL-series in late 1980's), you do know the difference. Voices in real life are not made from 2/3/4/5/6-sources, they're made from vast different echoes around the original sound source. So "the voice" is not SPOT, it's _area_ where sound comes from. And human ear can detect all those echoes when combining the result = voice.
Posted by A_MEN on Saturday 26 October 2002 08:37
True, True...but a well-made sacd sounds better in my ears than a well-made cd (enough 4 me) and they are not that expensive. cd 20€ sacd 25-30€, but if the recording is Lo-Fi or the music sucks, a better format won't make it any better...It's not how to make it more "realistic", the main idea is to make money by offering the customers a better listening experiense...atleast I'm willing to pay 4 that
Posted by ve2mrx on Saturday 26 October 2002 10:14
Wait, I have only 2 ears... 
Maybe Very high quality sound on two high quality channels played on two high quality speakers (or headphones, nothing beats that!) could be enough, don't you think? Two ears...
They are not "planar" sensitive, more like serially sensitive... (I mean sound is detected though a "pipe", not a multi-directional area. Except for LF sounds, as they are not position sensed by our ears in general).
Makes sence? Saving Private Ryan on good headphones is much better than audio equipment 10x the price with speakers, IMHO.
I stick by that until someone shows me that ears are internally sensitive to direction :4 ...
As for social gatherings, well, an expensive audio center is a much better conversation piece ;-)
Maybe Very high quality sound on two high quality channels played on two high quality speakers (or headphones, nothing beats that!) could be enough, don't you think? Two ears...
They are not "planar" sensitive, more like serially sensitive... (I mean sound is detected though a "pipe", not a multi-directional area. Except for LF sounds, as they are not position sensed by our ears in general).
Makes sence? Saving Private Ryan on good headphones is much better than audio equipment 10x the price with speakers, IMHO.
I stick by that until someone shows me that ears are internally sensitive to direction :4 ...
As for social gatherings, well, an expensive audio center is a much better conversation piece ;-)
Posted by Mastakilla on Saturday 26 October 2002 17:36
very nice and intresting article!
but if there is one thing id love to know about this is: what kinda copyprotection is on it, and how far are are we in cracking it?
and will it be possible to make sacd writers?
but if there is one thing id love to know about this is: what kinda copyprotection is on it, and how far are are we in cracking it?
and will it be possible to make sacd writers?
Posted by man on Saturday 26 October 2002 20:23
Something I not totally understand. Can anybody explain them to me.
1. From the theoretical point of view, the sound quality of SACD is 6 times better than the normal CD. (10*log64 dB/10*log2 dB, where 10*log2=3dB) I am not too sure about the loudspeakers on the market whether they have the capacity to response 100kHz as when they were designed, they only designed to optimize 20-20kHz. If the loudspeakers have much distortion at high frequency, what is the point of feeding high frequency quaility data into them?
2. I hope this question is not too techical. From the theory of Fourier transform, the sampling frequency must be at least twice of that of the maximum signal frequency. (that is why they choose 44.1k at the beginning of the normal CD) I notice that the SACD's samping rate is 2822.4 but the max recorded frequency is only 100kHz not 1.4Mhz. It seems to me that SACD is capable to reconstruct up 1.4MHz instead of 100kHz.
3. Does anybody got any idea of the record of the max frequency human being can hear?
=================
Answer to some of the posts.
Tiikeri, you are right about the source of the sound. But if you have only 1 to 1 conversation, I believe it can be reconstructed reasonably successful by SACD because the sampling rate is far too high for human ear to find any difference. However, I do not agree that it is because of the echo. At the end, it is all about how many overtures you can record and hear.
v22mrx, it is all about the delay of each channels to your ears. If you use headphone, you will cut off all the background noise you have in your room but you will lost the sense of directions. Besides, having a good subwoofer, your skin can feel it too. :7
1. From the theoretical point of view, the sound quality of SACD is 6 times better than the normal CD. (10*log64 dB/10*log2 dB, where 10*log2=3dB) I am not too sure about the loudspeakers on the market whether they have the capacity to response 100kHz as when they were designed, they only designed to optimize 20-20kHz. If the loudspeakers have much distortion at high frequency, what is the point of feeding high frequency quaility data into them?
2. I hope this question is not too techical. From the theory of Fourier transform, the sampling frequency must be at least twice of that of the maximum signal frequency. (that is why they choose 44.1k at the beginning of the normal CD) I notice that the SACD's samping rate is 2822.4 but the max recorded frequency is only 100kHz not 1.4Mhz. It seems to me that SACD is capable to reconstruct up 1.4MHz instead of 100kHz.
3. Does anybody got any idea of the record of the max frequency human being can hear?
=================
Answer to some of the posts.
Tiikeri, you are right about the source of the sound. But if you have only 1 to 1 conversation, I believe it can be reconstructed reasonably successful by SACD because the sampling rate is far too high for human ear to find any difference. However, I do not agree that it is because of the echo. At the end, it is all about how many overtures you can record and hear.
v22mrx, it is all about the delay of each channels to your ears. If you use headphone, you will cut off all the background noise you have in your room but you will lost the sense of directions. Besides, having a good subwoofer, your skin can feel it too. :7
Posted by Pio2001 on Tuesday 29 October 2002 01:36
Man,
1-There is no point in playing frequencies above 20 kHz on 20 kHz only equipment.
2-The amplitude definition of DSD becomes smaller as frequency rises. 100 kHz is given for a sensible amplitude. SACD should be able to play 1.4 MHz, but at the lowest existing level, somewhere around -100 or -140 db ,I don't know.
3-Asmathic children can hear up to 30,000 Hz.
1-There is no point in playing frequencies above 20 kHz on 20 kHz only equipment.
2-The amplitude definition of DSD becomes smaller as frequency rises. 100 kHz is given for a sensible amplitude. SACD should be able to play 1.4 MHz, but at the lowest existing level, somewhere around -100 or -140 db ,I don't know.
3-Asmathic children can hear up to 30,000 Hz.
Posted by Wee on Tuesday 29 October 2002 15:27
In addition:
1. Amplifiers have power bandwidths (+/- 3dB) that commonly exceed the 20hz-20kHz bandwidth. 5Hz-200kHz is easy for a good amp. A great deal of speakers are indeed still limited to 20 kHz. But many of those also reproduce sounds above that (e.g. B&W). Moreover, speakers are appearing reproducing sounds up to 50 or 70 kHz. In the bottom range, however, decent speakers are generally limited to 20 Hz or so and many do not go below 30 Hz. SACD is, however, capable of producing 1 Hz sounds. No way that an ordinary speaker (still placeable in your home) is going to reproduce that. So, in the bottom registers there is a limitation, in the upper registers much less so, provided you have the right speakers.
2. The Fourier transform, or the Nyquist theorem you're talking about, applies to sine waves. This explains the 2: max amplitude up, and max amplitude down. Good reproduction of a squarewave requires 8 to 9 times the sampling frequency. And than it is still not perfect. Perfect reproduction, infinite sampling rate. A wave also has its harmonics that are not accounted for by the theorem. Higher sampling rate also gives you better dynamic range. And do not forget that the bit depth of SACD is 1 bit whereas CD has 16 bit(although bitdepth is less important than sampling rate in reproducing sound). From this point of view SACD is 4 times "better" than CD. CD: 16 x 44.1 = 705.6 k, SACD 1 x 2822 = 2822 k, DVD-Audio: 24 x 96 = 2304 k.
3. The sounds above 20 kHz create "vibrations" in the inner ear. We do not "hear" those as true sound, like voice or a piano, but they do change the sound, es pecially in terms of "feeling". That is what you "hear", and yes it does make a lot of difference. SACDs sound like good vinyl.
1. Amplifiers have power bandwidths (+/- 3dB) that commonly exceed the 20hz-20kHz bandwidth. 5Hz-200kHz is easy for a good amp. A great deal of speakers are indeed still limited to 20 kHz. But many of those also reproduce sounds above that (e.g. B&W). Moreover, speakers are appearing reproducing sounds up to 50 or 70 kHz. In the bottom range, however, decent speakers are generally limited to 20 Hz or so and many do not go below 30 Hz. SACD is, however, capable of producing 1 Hz sounds. No way that an ordinary speaker (still placeable in your home) is going to reproduce that. So, in the bottom registers there is a limitation, in the upper registers much less so, provided you have the right speakers.
2. The Fourier transform, or the Nyquist theorem you're talking about, applies to sine waves. This explains the 2: max amplitude up, and max amplitude down. Good reproduction of a squarewave requires 8 to 9 times the sampling frequency. And than it is still not perfect. Perfect reproduction, infinite sampling rate. A wave also has its harmonics that are not accounted for by the theorem. Higher sampling rate also gives you better dynamic range. And do not forget that the bit depth of SACD is 1 bit whereas CD has 16 bit(although bitdepth is less important than sampling rate in reproducing sound). From this point of view SACD is 4 times "better" than CD. CD: 16 x 44.1 = 705.6 k, SACD 1 x 2822 = 2822 k, DVD-Audio: 24 x 96 = 2304 k.
3. The sounds above 20 kHz create "vibrations" in the inner ear. We do not "hear" those as true sound, like voice or a piano, but they do change the sound, es pecially in terms of "feeling". That is what you "hear", and yes it does make a lot of difference. SACDs sound like good vinyl.
Can someone please explain me how to get multichannel sound with sacd? I cannot find it anywhere how to do it. I have a STR-DB930 receiver from sony, a DVPS-900 DVD/SACD player and i have 5.1 speakers connected to my receiver.
There's a multi channel cd shipped with my player but i don't hear multichannel sound.... Thanks in advance, Oscar.
There's a multi channel cd shipped with my player but i don't hear multichannel sound.... Thanks in advance, Oscar.
oscar,
You need to connect your dvd/sacd player to your receiver via the six analogue outputs. sacd will NOT play via a digital output
bb
You need to connect your dvd/sacd player to your receiver via the six analogue outputs. sacd will NOT play via a digital output
bb
I would like to see the article explain more clearly how the 1-bit-ness of SACD affects things (as opposed to the 16-bit CD format)...
Tiikeri: what is the end goal of audio reproduction? To accurately reproduce a 'natural' audio experience? Maybe this is great if you have a talented artist and you can't hire them to sit in your living room and play whenever you want. If accuracy is the goal, then audiophiles strive to spend more and more money to achieve a diminishing distance from the "real thing" of a good concert. But for pop music and movies, there generally isn't a "real thing" to reproduce - the audio recording is actually a heavily manipulated production that is engineered to entertain an audience that is either sitting in a movie theater (with a decent sound system, but definitely not planar), or a home theater (generally lower quality than movie theaters), or simply listening to a car radio or boombox.
Yes, the best recordings are made to sound good on a wide range of equipment, but the main thing is that they are made to sound good ON EQUIPMENT. Does SACD allow for a better-sounding, more "emotional" experience? Probably, if the original sound was great and some of that greatness is masked by conventional CDs. But as we approach closer and closer fidelity to the original sound, how desirable is that realism if you can hear the fart of the singer or the train passing by the concert hall? Gulliver discovered that the most beautiful Brobdingnagians appeared hideous when the dirt in their pores was readily apparent... Just a thought.
Tiikeri: what is the end goal of audio reproduction? To accurately reproduce a 'natural' audio experience? Maybe this is great if you have a talented artist and you can't hire them to sit in your living room and play whenever you want. If accuracy is the goal, then audiophiles strive to spend more and more money to achieve a diminishing distance from the "real thing" of a good concert. But for pop music and movies, there generally isn't a "real thing" to reproduce - the audio recording is actually a heavily manipulated production that is engineered to entertain an audience that is either sitting in a movie theater (with a decent sound system, but definitely not planar), or a home theater (generally lower quality than movie theaters), or simply listening to a car radio or boombox.
Yes, the best recordings are made to sound good on a wide range of equipment, but the main thing is that they are made to sound good ON EQUIPMENT. Does SACD allow for a better-sounding, more "emotional" experience? Probably, if the original sound was great and some of that greatness is masked by conventional CDs. But as we approach closer and closer fidelity to the original sound, how desirable is that realism if you can hear the fart of the singer or the train passing by the concert hall? Gulliver discovered that the most beautiful Brobdingnagians appeared hideous when the dirt in their pores was readily apparent... Just a thought.
Copy protection you ask?
After reading the below my guess would be "don't hold your breath"
Well, here's the lowdown straight from Sony:
Your guarantee of audio purity.
No-one, especially audiophiles, likes to get sold music that's been poorly mastered or is of inferior quality.
For this reason Super Audio CDs has used Pit Signal Processing technology (PSP) to embed a Water-mark, consisting of a controlled array of microscopic pits, on the surface of the disc. PSP enables two types of Water-marks: an "invisible" Watermark, which can only be detected by the Super Audio CD player, and a "visible" Watermark (maker's discretion), which is imprinted on the disc in the form of text or an image and allows you to easily identify original Super Audio CDs.
If a counterfeit disc is inserted in the Super Audio CD player, the player detects the absence of the invisible Watermark and prevents playback. Both types of Watermarks are almost impossible to duplicate clearly, making it easy to distinguish between real and pirated discs, especially for the visible Watermark, which is possible to identify at a glance.
After reading the below my guess would be "don't hold your breath"
Well, here's the lowdown straight from Sony:
Your guarantee of audio purity.
No-one, especially audiophiles, likes to get sold music that's been poorly mastered or is of inferior quality.
For this reason Super Audio CDs has used Pit Signal Processing technology (PSP) to embed a Water-mark, consisting of a controlled array of microscopic pits, on the surface of the disc. PSP enables two types of Water-marks: an "invisible" Watermark, which can only be detected by the Super Audio CD player, and a "visible" Watermark (maker's discretion), which is imprinted on the disc in the form of text or an image and allows you to easily identify original Super Audio CDs.
If a counterfeit disc is inserted in the Super Audio CD player, the player detects the absence of the invisible Watermark and prevents playback. Both types of Watermarks are almost impossible to duplicate clearly, making it easy to distinguish between real and pirated discs, especially for the visible Watermark, which is possible to identify at a glance.
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