Audio D/A converter

[dovplay]

<font color='#000000'>This is a general question on audio D/A converters. &nbsp;Is there a really big difference (noticeable or otherwise) between a 96kHZ 24 bit converter and a 192kHZ 24 bit converter. &nbsp;I know that the 192 is better and more advanced, but does it really make that big of a difference and if it does, how so?

Thanks!</font>

[Blizz]

<font color='#000000'>In a word..yep! But I will qualify this by saying that if you are running a &quot;budget HiFi system&quot; and replace your budget DVD player that has budget DAC's with a super slick DVD unit (eg. Denon 2900) with super slick Burr-Brown DAC's, then nup it's not gonna make much difference at all. Your HiFi system is only as good as the weakest component. Like a garden hose that starts 2 feet in diameter but reduces to ¼ inch at the nozzle, the 2 foot diamter section of hose will help push more water to the nozzle, but the nozzle will only ever let ¼ inch stream escape. In other words, you could have the best speakers, DVD, leads, cable but if your amp and DAC's within are ordinary, then you're going to get ordinary sound.

A high quality DAC like the Burr-Brown Hi-Res PCM1738E 24bit 192kHz, very basically, controls the conversion of a digital signal to an analogue signal that eventually ends up at your speakers. The better the DAC the better the S/N (signal to noise) processing, thus ultimately resulting in your system producing it's optimum fidelity. BLIZZ</font>

[BachStrad]

I understand buying a DVD player with outstanding video capabilities. But for audio, what if you plan to run your dvd through the DACs of a high quality pre-amp/amp--specifically one with an asynchronous sample-rate converter, like the Analog Device AD1896?

In other words, I don't see the point of buying premium DACs for both the DVD player & the AV pre-amp. I'd prefer to save money on the audio part of the dvd player & reinvest it in a top-line pre-amp. Any advice?

[MDS]

In other words, I don't see the point of buying premium DACs for both the DVD player & the AV pre-amp. I'd prefer to save money on the audio part of the dvd player & reinvest it in a top-line pre-amp. Any advice?

I think you have the right idea. Most likely you are going to be using a digital connection to the pre-amp or receiver and it will be it's DACS that determine the sound quality. Although some people swear by the use of external dacs, really it's pointless. The difference between dacs is very slight - nobody can reliably tell the difference between burr brown, analog devices, or cirrus dacs.

[tbewick]

'In a word..yep! But I will qualify this by saying that if you are running a "budget HiFi system" and replace your budget DVD player that has budget DAC's with a super slick DVD unit (eg. Denon 2900) with super slick Burr-Brown DAC's, then nup it's not gonna make much difference at all. Your HiFi system is only as good as the weakest component.' - Blizz

In all likelihood your loudspeakers are almost always the weakest component.

Rane Audio has a helpful discussion of this topic. It is directed more towards analogue to digital conversion, but it is still interesting and relevant:

http://www.rane.com/par-d.html (see data converter bits)
http://www.rane.com/note137.html

I read this some time ago, but here are what I would consider the important conclusions:

'Here is what is gained by using 20-bits:

* 24 dB more dynamic range
* 24 dB less residual noise
* 16:1 reduction in quantization error
* Improved jitter (timing stability) performance

And if it is 24-bits, add another 24 dB to each of the above and make it a 256:1 reduction in quantizing error, with essentially zero jitter!

As stated in the beginning of this note, with today's technology, analog-to-digital-to-analog conversion is the element defining the sound of a piece of equipment, and if it's not done perfectly then everything that follows is compromised.'

'...can the human ear tell the difference. In most cases, once you go beyond true 16-bits, the answer is no. All benefits above 16-bits/48 kHz are very small refinements, not monumental improvements. What really is going on, is that the advertised "16-bit/48 kHz" recordings of yesterday weren't. They used 16-bit converters but their accuracy was not 16-bits, it was more like 14-bits. Similarly today, the advertised "24-bit" converters are not 24-bit accurate, but they are certainly at least 18-bit accurate, and that makes an audible difference. So, if you can find a true 16-bit system and compare it with a typical 24-bit system of today, they will sound very nearly identical. And the sampling rate getting faster makes even less of an audible difference. For example if you compare a typical 16-bit/96 kHz system against a 24-bit/48 kHz, you will pick the 24-bit system every time. If you have a choice, always choose more bits, over a higher sampling rate.]'

You should also note that the analogue-to-digital converter (ADC) performance is usually more important than digital-to-analogue converter performance. There is, of course, nothing you can do about the quality of the original recording and ADC used. It is worth saying that even the earliest digital audio production equipment was considered very good:

'...experience has shown that even the first generation of digital systems are as good as some of the best analogue systems which have been evolved over many years. Digital tape recorders, of which several have been developed by the broadcasting organisations and record companies, have performance qualities which are far superior to the best analogue studio recorders.'

- Practical Hi-Fi Sound, R. Driscoll, page 63-64, 1980 Hamlyn.

[mtrycrafts]

<font color='#000000'>This is a general question on audio D/A converters. &nbsp;Is there a really big difference (noticeable or otherwise) between a 96kHZ 24 bit converter and a 192kHZ 24 bit converter. &nbsp;I know that the 192 is better and more advanced, but does it really make that big of a difference and if it does, how so?

Thanks!</font>


As some posted, or left out, there are no recording today or in the past that uses 96dB red book dynamic range in the recordings. And, what is the use of 96kHz sampling if you cannot hear it?
Simply, use what you have now. Spend your $$$ on software, room acoustics, or speakers.

[tbewick]

I'm not sure about that, mtrycrafts. Chris made a similar point on an earlier thread. The Rachmaninov performance in Shine has peaks up to 108 dB (dolby Digital). Certainly many Dolby Digital and DTS soundtracks do make full use of the headroom available compared to 16 bits. I'm also pretty sure that Telarc's hybird SACD/Audio CD version of the 1812 Overture has a very large dynamic range. On the cover, it has a warning about 'DSD (direct stream digital) cannons'!

I'd also say that if you have 24 bit/96kHz playback technology available, then why bother converting down to 16 bit/44.1 kHz? There's no reason to reduce the dynamic range of a recording for the sake of it. Some people with high quality systems may benefit from the greater dynamic range available. I would think that the benefit of extended dynamic range would be in better bass and sub-bass reproduction (extra thump in the timpani, depth in the low notes of a pipe organ, grand piano, etc.).

[tbewick]

'there are no recording today or in the past that uses 96dB red book dynamic range in the recordings' - Mtrycrafts

Hi mtrycrafts,

I think that this is a common misconception, which I used to have, that people think about dynamic range. You have to consider the background noise present in most home listening environments, which is usually 30 dB (~20 dB at night). This reduces the dynamic range by 30 dB. It is also worth knowing that the dynamic range of audio CD can be increased using dither, which can increase the dynamic range to 120 dB (Digital Domain, Bob Katz's site, has more about this).

With a Dolby Digital/DTS soundtrack, you could get around 85 dB of dynamic range in a very high quality playback system. I think that this is the spec required for THX cinemas. The Audioholics site has more details about this in the article about noise control/acoustics. With audio CD, I don't think you could get 85 dB of dynamic range, it would be 20 dB less than this (65 dB). Maybe you can get more dynamic range with dither. I don't know enough about dither to say for certain.

[WmAx]

You have to consider the background noise present in most home listening environments, which is usually 30 dB (~20 dB at night).

The typical averaged noisefloor of a home environment averages around 40-45 dB. A noisefloor of 20-30dB can be obtained commonly in the following ways:

(1) special acoustic isolation room conditions(this can include suspended room constructions, exceptional building structures, et cetera)
(2) rural dwelling, away from traffic and other external noise sources, with all sound producing devices inside of the house turned off(heating, A/C, et cetera)


With audio CD, I don't think you could get 85 dB of dynamic range, it would be 20 dB less than this (65 dB). Maybe you can get more dynamic range with dither. I don't know enough about dither to say for certain.

The only time where the bit-depth of CD is not sufficient for playback is under unique test conditions that are designed to exploit the difference or generally undesirable conditions. For example, it would be obvious that 16 bits was noiser than 24 bits if one turned up the volume to levels above actual listening levels, using a special recording with very low noise levels. 16 bits would not be sufficient to realisticly play back a high school marching band in a very quiet practice room that suddenly starts playing a high SPLs. This would end up being in the 125-130dB peak SPL ranges at close distance. Assuming an extraordinaryly quiet room (20dB), this would require an *effective SNR of about 110dB. But the desirability to reproduce such dangerous levels is highly questionable. Consideration: a very good full range floorstanding speaker with generous bass capabilities that is not limited by amplification is generally capable of 100-105dB(which equals 80-85dB SNR in that extraordinary quiet 20dB environment, and much worse in actual average environments) at the listening position before excessive distortion takes effect. In order to be able to use the high school band recording as specified above, this would require an extraordinary speaker such as a large line array or very efficient, very large horn-based system.

-Chris

[tbewick]

'The only time where the bit-depth of CD is not sufficient for playback is under unique test conditions that are designed to exploit the difference or generally undesirable conditions.' - Chris

So are you saying that DTS/Dolby Digital are only useful in the sense of having multichannel capability? In a theatre environment, the greater headroom available with DTS/Dolby Digital is used in many films. You wouldn't be able to get the same sound quality at high volumes with 16 bit as you do with higher bit rate formats. I don't know much about dither, but I'm guessing that 24 bit dithered to 16 bit sounds worse than true 24 bit.

'Assuming an extraordinaryly quiet room (20dB), this would require an *effective SNR of about 110dB. But the desirability to reproduce such dangerous levels is highly questionable.'

The fact that some people do enjoy listening at Dolby reference level in the cinema would suggest that such volumes are worth reproducing. These high volumes, normally in bass and sub-bass, aren't dangerous over short exposure times.

'Consideration: a very good full range floorstanding speaker with generous bass capabilities that is not limited by amplification is generally capable of 100-105dB(which equals 80-85dB SNR in that extraordinary quiet 20dB environment, and much worse in actual average environments) at the listening position before excessive distortion takes effect.'

Such high volumes (and higher) can be reproduced using subwoofers (effectively bi-amping with active subs). Distortion isn't a huge problem because our ears are less sensitive to distortion at low frequencies.

Many forms of music, symphonic works, rock music etc. have peak volumes way above the digital clipping point of audio CD. To me, therefore, it makes sense to want to preserve these peak volumes in the recording. Admittedly, as you point out, you'd need very capable equipment (and most likely some form of acoustical treatment) to accurately reproduce and enjoy such high volumes in the home.

[WmAx]

So are you saying that DTS/Dolby Digital are only useful in the sense of having multichannel capability? In a theatre environment, the greater headroom available with DTS/Dolby Digital is used in many films.

Show me analysis of a soundtrack that can not be encapsulated by 16 bit.

You wouldn't be able to get the same sound quality at high volumes with 16 bit as you do with higher bit rate formats. I don't know much about dither, but I'm guessing that 24 bit dithered to 16 bit sounds worse than true 24 bit.

Why would(or could it) sound worse? Unless you purposely use a special case as I specified earlier or used a poor quality conversion process.

The fact that some people do enjoy listening at Dolby reference level in the cinema would suggest that such volumes are worth reproducing. These high volumes, normally in bass and sub-bass, aren't dangerous over short exposure times.

I do not know what you base 16 bit's inadequecy upon.

Such high volumes (and higher) can be reproduced using subwoofers (effectively bi-amping with active subs). Distortion isn't a huge problem because our ears are less sensitive to distortion at low frequencies.

Of course, you can adjust your subwoofer to have 10+ dB higher gain than the mains at a given reference(I suppose that many people do this). This has no bearing on the bit depth.

Many forms of music, symphonic works, rock music etc. have peak volumes way above the digital clipping point of audio CD.

Please, refer to a single commercial[as opposed to a demo designed soley to exceed the range] example.

To me, therefore, it makes sense to want to preserve these peak volumes in the recording. Admittedly, as you point out, you'd need very capable equipment (and most likely some form of acoustical treatment) to accurately reproduce and enjoy such high volumes in the home.

I think you are thinking of something else. To use the full range of 16 bits in a very quiet(30dB)environment requires speakers/system that can produce a peak range in excess of 120dB SPL. In fact, the noise floor of recordings is severely limited by the microphones and recording environments. Any microphoned recording will have an audible noisefloor that is not even 16 actual bits unless very heavy digital noise reduction techniques are used to create digital silence. The example I gave earlier of the band class practice room is theoretical, and requires some extraordinary conditions and results in something that would not be created for commerciall application(s).

-Chris

[tbewick]

My simplistic analysis was seeing that Dolby Digital is 18 bit, and has a dynamic range of 105 dB, then anything above 96 dB for 16 bit would result in clipping. You're saying that 16 bit has a dynamic range of 120 dB? If this is the value for 16 bit, then my assessment is wrong. I thought that with dither, you add a small amount of noise to increase the dynamic range. If you're working in 18 bit, then you would need to add less dither compared to 16 bit and therefore have less noise. What you are saying is, I'm guessing, is that this noise would be so quiet as to be inaudible.

I'll probably do some background reading on this.:confused:

[WmAx]

My simplistic analysis was seeing that Dolby Digital is 18 bit, and has a dynamic range of 105 dB, then anything above 96 dB for 16 bit would result in clipping. You're saying that 16 bit has a dynamic range of 120 dB? If this is the value for 16 bit, then my assessment is wrong. I thought that with dither, you add a small amount of noise to increase the dynamic range. If you're working in 18 bit, then you would need to add less dither compared to 16 bit and therefore have less noise. What you are saying is, I'm guessing, is that this noise would be so quiet as to be inaudible.

I'll probably do some background reading on this.:confused:

The issue is that:

(1) No real source material(maybe their is a special demo that exists as I have specified, but not actual commercial releases intended for practical use) even uses the 96dB range of 16 bits.

(2) You have to account for the noisefloor of the room used for playback. A 30dB noisefloor(you can't hear much below this noisefloor, but to be safe, I'll assume that you can easily hear 10 dB under the noisefloor) of an extraordinarly quiet enviroment, and that the theoretical source material actually has content at this low of a level. So let's -10 dB from 96 db = 86 dB. 30dB(floor) + 86dB = 116 dB(a safe estimate, assuming -10 dB under noisefloor of this super-quiet theoretical environment is possible) SPL capability.

In reality, the average playback room's noisefloor will be in the 40-45 dB range, and the recording(even very high fidelity classical material from top notch labels) will have an actual noisefloor that is much noisier than the floor at the bottom of 16 bits, except for in cases where digital noise reduction is used and/or other digital manipulation techniques.

-Chris

[mtrycrafts]

'there are no recording today or in the past that uses 96dB red book dynamic range in the recordings' - Mtrycrafts

Hi mtrycrafts,

I think that this is a common misconception, which I used to have, that people think about dynamic range. You have to consider the background noise present in most home listening environments, which is usually 30 dB (~20 dB at night). This reduces the dynamic range by 30 dB. It is also worth knowing that the dynamic range of audio CD can be increased using dither, which can increase the dynamic range to 120 dB (Digital Domain, Bob Katz's site, has more about this).

With a Dolby Digital/DTS soundtrack, you could get around 85 dB of dynamic range in a very high quality playback system. I think that this is the spec required for THX cinemas. The Audioholics site has more details about this in the article about noise control/acoustics. With audio CD, I don't think you could get 85 dB of dynamic range, it would be 20 dB less than this (65 dB). Maybe you can get more dynamic range with dither. I don't know enough about dither to say for certain.


Not long ago I was reading an evaluation by a recording engineer, John Eargle, I believe. He indicated the best classical that is available has 70 dB dynamic range recorded.
At 105 dB spl max, excluding a sub, 90 dB would need a 15 dB noise floor room. And, with a 10 dB over on a sub, that would be a 25 dB room.
I tend to discount unrealistic needs. I am also curious which recording has such high dynamic range recorded:D

[tbewick]

Hi mtry,

As I said in my earlier post, I find this all very confusing. I've heard the S/N ratio of 16 bit given as 91.3 dB before.

At the end of the day, I just listen depending on how good the performance is. A lot of the time, I'm more than satisfied with LP, despite the occasional crackle and distortion etc. Yesterday I listened to a very good LP, a Decca digital recording - a Prokofiev violin concerto with the London Philharmonic - superb sound quality. One thing that CD has going against it are the botched up, over-processed releases of some classical CD's. If you'd only ever heard rubbish like this, then it would be no surprise if you were put off CD.

I don't have a SACD or DVD Audio player at the moment, but I might get one in the future out of sheer curiosity. I bet the SACD Telarc 1812 Overture would be worth a listen.

Back to the original question, I do think it's worth getting a 24 bit DAC, because as the Rane Note said, this ensures at least 18 bit (and hence 16 bit) accuracy. You should review the specs for the CD player or digital receiver's digital output component as well, looking for the usual things (signal-to-noise, harmonic distortion, frequency response). On wikipedia, there are other measures given for DAC performance, but I've never seen these quoted in specifications.

[MDS]

As I said in my earlier post, I find this all very confusing. I've heard the S/N ratio of 16 bit given as 91.3 dB before.

If you want a rule of thumb - each bit is worth roughly 6 dB of dynamic range, so the theoretical max for 16 bit is 96 dB. To put all of this into perspective just remember what sampling is all about - a sample is a value assigned to represent the amplitude of the original analog signal at points in time. With 16 bits (the 'bit depth') you have 65,536 possible values (2**16). The waveform has both a positive and negative component (it oscillates around zero as do all sine waves). Therefore, the values can range between -32768 and +32,767 (the most significant bit is the sign, leaving 15 bits of actual resolution). In a simplistic sense, it's like 'rate this sound on a scale of -32768 to +32767.

WmAx is trying to point out that in the real world things are complicated by the noise floor. You won't be able to faithfully capture the full 96 dB range because of inherent noise in the environment and the recording equipment itself. If the recording level is too high and the actual sound would not fall into the available range based on the bit depth (that is determined by the ADC), then the signal clips; ie the max value is recorded because you cannot exceed the max value: if (sample >= 32,6767) sample = 32,767. That is 0 dBFS and as I pointed out in another thread, if you have multiple samples in a row at a max amplitude that is the definition of digital clipping.

You can eliminate clipping by a) reducing the recording level or b) reducing the noise floor. It's true that it isn't possible to capture the full effect of sound that is greater than the bit depth's available range if the recording level cannot be set lower or the noise floor cannot be reduced appreciably - but for most music 16 bits can fully capture the recording adequately.

We shouldn't get too bogged down with 'dynamic range' because the defintion of dynamic range is the difference between the softest and loudest parts and save the odd Telarc orchestra recording there isn't any music that comes close to using the 96 dB theoretical range of the 16 bit CD format. What I think is more important is the 'crest factor' - the difference between the average level and the peak level and that is often confused for dynamic range. Modern CDs (at least the rock/pop/disco/electronica type stuff I have) has very poor crest factor - 6 dB on average. Watch the peak level meters in CoolEdit and you will see what I mean. When the music is highly compressed and aggressive limiters are used, we don't even get to realize the potential of the current 16 bit format, so why pull our hair out arguing over the merits of increased bit depth?

Note: Dither is random noise added to the signal. It has the effect of reducing the perceived noise floor because the ear is less sensitive to the random noise than real distortion caused by quantization error. Any time you reduce the bit depth, like when you go from a 24 bit master recording to 16 bit for delivery on CD, dither must be added. If you playback a 16 bit recording using a 24 bit dac, the high order 8 bits are zero. You gain a little precision for the calculations but it won't magically make the 16 bit recording sound like it was originally captured at 24 bits.

[tbewick]

'We shouldn't get too bogged down with 'dynamic range' because the defintion of dynamic range is the difference between the softest and loudest parts and save the odd Telarc orchestra recording there isn't any music that comes close to using the 96 dB theoretical range of the 16 bit CD format.' - MDS

My confusion arose because the stated dynamic range of Dolby Digital is 105 dB and Dolby Digital is 18 bits. MLP (DVD Audio) is also 18 bits. In the Dolby white paper - 'Are Movies too Loud?' - at reference level, the paper gives examples of soundtracks which have peaks in the 110 dB region. Therefore I thought that seeing as 16 bit audio CD has a possible dynamic range of 96 dB, these peaks would not be reproduced with the same sound quality. I see now that I misinterpreted the meaning of 'dynamic range' or 'crest factor' (see below).

'What I think is more important is the 'crest factor' - the difference between the average level and the peak level and that is often confused for dynamic range'

Oddly enough, the Dolby paper defines dynamic range in this way-

'An unfortunate misuse of the term “dynamic range” suggests the value of the maximum peak level. Here we are using the term to show the range between average levels and the loudest peak value events on the soundtrack. Program with little change in level, whether close to peak level of the recording medium, or much lower, has little dynamic range. Program with sudden changes in level (a sudden gunshot in a quiet desert scene) has a high dynamic range.'

I think this Rane note (S/N) helps here:

'All these thing must be stated for a S/N spec to have meaning. Simply saying a unit has a SNR of 90 dB means nothing, without giving the reference level, measurement bandwidth, and any weighting filers. A system's maximum S/N is called the dynamic range.'

I don't mean to add any more confusion to this thread, but I've seen that 8 bits is commonly given a dynamic range of 70 dB. You'd therefore think that this was very good, and comparable to a direct metal mastered vinyl, but the noise is far more audible with 8 bit. So this goes with what the Rane Note says, about needing to state a reference level, etc. for the S/N measurement.

'Modern CDs (at least the rock/pop/disco/electronica type stuff I have) has very poor crest factor - 6 dB on average. Watch the peak level meters in CoolEdit and you will see what I mean. When the music is highly compressed and aggressive limiters are used, we don't even get to realize the potential of the current 16 bit format, so why pull our hair out arguing over the merits of increased bit depth?'

I did notice this on the Interpol and Frand Ferdinand tracks I've ripped. These sorts of recordings sound better at low volumes. An older recording which sounds better (Stone Roses) doesn't have much more dynamic range (around 7-8 dB), but is visibly less compressed on Cool Edit. The 'hotness' of modern pop must result from the greater use of compressors and limiters.

I think it's fair to say that bit depth isn't only about dynamic range, but about perceived sound quality. The Rane Note quote I posted earlier reflects this-

'So, if you can find a true 16-bit system and compare it with a typical 24-bit system of today, they will sound very nearly identical. And the sampling rate getting faster makes even less of an audible difference.' (which answers the original question)

[MDS]

Dynamic range is one of those terms that is used in different contexts to mean different things but the real definition is the difference between the softest and loudest parts. The human ear is said to have a dynamic range of 130 dB which would mean we can hear from 0 dB (the softest perceivable sound in this context) all the way up to 130 dB (the threshold of pain).

The Dolby definition stated is exactly what I understand to be crest factor.

Oh well, it's the same in other disciplines. The term 'proxy' means many different things in computer science but ask anyone with at least some familiarity with computers and they will most often tell you that a proxy is a firewall.

[mtrycrafts]

My simplistic analysis was seeing that Dolby Digital is 18 bit, and has a dynamic range of 105 dB, then anything above 96 dB for 16 bit would result in clipping. You're saying that 16 bit has a dynamic range of 120 dB? If this is the value for 16 bit, then my assessment is wrong. I thought that with dither, you add a small amount of noise to increase the dynamic range. If you're working in 18 bit, then you would need to add less dither compared to 16 bit and therefore have less noise. What you are saying is, I'm guessing, is that this noise would be so quiet as to be inaudible.

I'll probably do some background reading on this.:confused:

I think you are confusing the 105 dB spl level for reference levels in the speakers, excluding the sub, as needing a bit rate that is 105 dB dynamic range as well. That is what I am gathering form all your posts.
That is not the case at all, as the 16 bit CD is at 105 dB spl at full scale signals, 0 dBfs.
I think what you are missing is that you believe that the CD/DVD DD must have a 0 dB spl nose floor on it. It doesn't, absolutely not. 96 db 16 bit less from 105 gives you a CD floor of 6 dB spl above absolute 0. What good is that in a studio or home where the noise floor is up in the range of 20dB spl and above? That 14+ dB is doing nothing.
This also applies to the LFE that has 115dB at 0 dBfs. Less 96, and the floor is 19 dB spl, still below the room stuff.

[mtrycrafts]

The issue is that:

(1) No real source material(maybe their is a special demo that exists as I have specified, but not actual commercial releases intended for practical use) even uses the 96dB range of 16 bits.

(2) You have to account for the noisefloor of the room used for playback. A 30dB noisefloor(you can't hear much below this noisefloor, but to be safe, I'll assume that you can easily hear 10 dB under the noisefloor) of an extraordinarly quiet enviroment, and that the theoretical source material actually has content at this low of a level. So let's -10 dB from 96 db = 86 dB. 30dB(floor) + 86dB = 116 dB(a safe estimate, assuming -10 dB under noisefloor of this super-quiet theoretical environment is possible) SPL capability.

In reality, the average playback room's noisefloor will be in the 40-45 dB range, and the recording(even very high fidelity classical material from top notch labels) will have an actual noisefloor that is much noisier than the floor at the bottom of 16 bits, except for in cases where digital noise reduction is used and/or other digital manipulation techniques.

-Chris


I am not sure but I think he is equating max spl with the equivalent bit rate. I think I explained it properly that any bitrate below noise floor is wasted and not used but applied at the top end. That is what you are also saying to him.

[mtrycrafts]

Hi mtry,

As I said in my earlier post, I find this all very confusing. I've heard the S/N ratio of 16 bit given as 91.3 dB before.

At the end of the day, I just listen depending on how good the performance is. A lot of the time, I'm more than satisfied with LP, despite the occasional crackle and distortion etc. Yesterday I listened to a very good LP, a Decca digital recording - a Prokofiev violin concerto with the London Philharmonic - superb sound quality. One thing that CD has going against it are the botched up, over-processed releases of some classical CD's. If you'd only ever heard rubbish like this, then it would be no surprise if you were put off CD.

I don't have a SACD or DVD Audio player at the moment, but I might get one in the future out of sheer curiosity. I bet the SACD Telarc 1812 Overture would be worth a listen.

Back to the original question, I do think it's worth getting a 24 bit DAC, because as the Rane Note said, this ensures at least 18 bit (and hence 16 bit) accuracy. You should review the specs for the CD player or digital receiver's digital output component as well, looking for the usual things (signal-to-noise, harmonic distortion, frequency response). On wikipedia, there are other measures given for DAC performance, but I've never seen these quoted in specifications.


Bit rate and S/N are not the same. Bit rate is the ability to encode between the loudest signal and the softest signal. So far, there has yet to be a recording much more than 70dB dynamic range on the master.

[mtrycrafts]

Dynamic range is one of those terms that is used in different contexts to mean different things but the real definition is the difference between the softest and loudest parts. The human ear is said to have a dynamic range of 130 dB which would mean we can hear from 0 dB (the softest perceivable sound in this context) all the way up to 130 dB (the threshold of pain).

The Dolby definition stated is exactly what I understand to be crest factor.

Oh well, it's the same in other disciplines. The term 'proxy' means many different things in computer science but ask anyone with at least some familiarity with computers and they will most often tell you that a proxy is a firewall.


Yes, while the ear has that dynamic range, special conditions need to be in place for real world:D Since the surrounding space is not anechoic, the noise floor establishes the low limit at any given time.
I think he is confusing the max spl levels with the equivalent bit rates. DD doesn't need that 18 bits at all as you can still get plenty volume with less bits recorded. Two different issues as an amp can amplify a very small signal to any level you want, practically speaking.

[tbewick]

mtrycrafts/WmAx/MDS,

I know that this is off-topic, but do any of you know of any papers or books that have measured (understandable) data on digital audio performance? I did pick up a book today written by tech people at Sony (Digital Audio Technology, 4th edition, J. Maes & M. Vercammen, Focal Press 2001) which maintains that SACD and DVD Audio sound better than 16 bit CD audio.

The Sony book did give definitions of dynamic range (DR) and signal-to-noise:

DR = max. signal level (RMS)/RMS level of quantization noise without signal

S/N = signal level (RMS)/RMS level of quantization noise with signal

It states the dynamic range of CD as 'more than 90 dB', with a S/N of 90 dB.

[WmAx]

I know that this is off-topic, but do any of you know of any papers or books that have measured (understandable) data on digital audio performance?

You can find SNR and DR measurements for many cd players in Stereophile's product archive and you can find many 3rd party measurements of soundcards in 16 bit mode online with a search.

I did pick up a book today written by tech people at Sony (Digital Audio Technology, 4th edition, J. Maes & M. Vercammen, Focal Press 2001) which maintains that SACD and DVD Audio sound better than 16 bit CD audio.

What do they specify as perceptual references, to back themselves up? If they do not back themselves up, this reduces their credibility substantially, especially in a published technical paper or book. Makes you wonder, if they will go out on a limb and make this up, what else is being falsified?


It states the dynamic range of CD as 'more than 90 dB', with a S/N of 90 dB.

You can routinely find DACs that can achieve -96dB noise level and DR of 94 - 95 dB in modern equipment. But even 90dB is more than sufficient for any realistic playback purposes. Not even the best quality classical recording is going to require 90dB[except for the possible special exceptions I made clear earlier] for playback purposes.

-Chris

[mtrycrafts]

I did pick up a book today written by tech people at Sony (Digital Audio Technology, 4th edition, J. Maes & M. Vercammen, Focal Press 2001) which maintains that SACD and DVD Audio sound better than 16 bit CD audio.
.


Foster, Edward J. "Evolutionary or Super Audio Revolutionary? Audio, Nov 1999, page 40-47.

This is a Sony demo of SACD. Unfortunately they were caught cheating...
"When I pushed the point, the engineer admitted to adding a bit of reverb and otherwise toying around to make the sound 'more natural.'

[tbewick]

'You can find SNR and DR measurements for many cd players in Stereophile's product archive and you can find many 3rd party measurements of soundcards in 16 bit mode online with a search.' - Chris

I was thinking more of papers or books that detail the sound quality of 16 bit or of DAC performance/testing. How do Stereophile's tests do this? What are the characteristics of the noise produced when dithering and how does it change with programme? Most importantly, how audible is this noise? I would rather have text references as information on the internet is less likely to be accurate.

Most books I've looked at on the subject of hi-fi do not provide any experimental data at all. Some, like the Audio Amplifier Design Handbook, D. Self, present rants/philosophical ramblings and dismissive remarks that you would not find in any other serious scientific textbook.

'Foster, Edward J. "Evolutionary or Super Audio Revolutionary? Audio, Nov 1999, page 40-47.

This is a Sony demo of SACD. Unfortunately they were caught cheating...
"When I pushed the point, the engineer admitted to adding a bit of reverb and otherwise toying around to make the sound 'more natural.'' - mtrycrafts

I would hardly call this a scientific way of dismissing SACD. Does this book have anything more substantive?

[WmAx]

I was thinking more of papers or books that detail the sound quality of 16 bit or of DAC performance/testing.

I don't know what you mean by 'detail the sound quality of 16 bit'. The bit depth has to do with signal to noise; nothing more.

How do Stereophile's tests do this?

You can coorelate measurements with established perceptual papers on each parameter(frequency response, thd, noise floor, etc.). However, in most cases, the measurements are better than is required for human hearing. But this still, is a slew of other parameters. Since we are on the specific subject of bit depth; I do not understand how one can 'detail the sound quality of 16 bit', except for the noisefloor. Depending on the specific dither used, the lowest level sounds could be slightly effected; but for this to be audible would require extaordinary circumstances(program material encoded in the first few bits only, turning up volume to levels well beyond what would be used for listening to actual music)

What are the characteristics of the noise produced when dithering and how does it change with programme?

It does not change with program. It is a steady state noise applied to the bottom bit(exact bit depth dependant on the particular system used to capture the audio, or if a reduced bit; 24-->16; this is specified and controlled by the audio engineer. The characteristic of the noise shape spectral distribution also varies, dependant on the same. A high quality dither will apply most of the noise to very high frequencies, so that it is less audible than if a constant white noise was applied to all bands, for example. )

Most importantly, how audible is this noise?

That depends on the specific dithering algorythm used. However, in a good process, it sounds exactly like a constant white noise, if you amplify it enough to make it audible in absence of other signals. If you desire, I can prepare a file with a standard high quality dither(or multiple dithers) amplified to where it is clearly audible.


I would hardly call this a scientific way of dismissing SACD. Does this book have anything more substantive?

It's really a dead end to look for refutations. What is there to refute? DSD was never proven to be an advantage in the first place. Where/when did Sony prove DSD was better sounding compared to PCM?

-Chris

[tbewick]

'You can coorelate measurements with established perceptual papers on each parameter(frequency response, thd, noise floor, etc.). However, in most cases, the measurements are better than is required for human hearing. But this still, is a slew of other parameters. Since we are on the specific subject of bit depth; I do not understand how one can 'detail the sound quality of 16 bit', except for the noisefloor.'

Does this mean that two 16 bit systems with identical S/N and dynamic range will be audibly identical? I would like references to papers or books which prove this. One of the claims of the Sony textbook is something to do with SACD versus CD and the need for D/A converters:

'the need for high-precision D/A converter circuitry versus the possiblity to even replace D/A circuitry by simple low-pass filtering'

and 'the need for noise shaping, digital filters, interpolation versus much reduced need for such circuitry'.

I don't know enough about CD to comment on these claims, that was the point of my earlier question - do you know of any papers or books that have measured (understandable) data on digital audio performance?

'It's really a dead end to look for refutations.'

Rather than dismissive remarks about SACD, I'm looking for proper tests comparing it to CD.

[mtrycrafts]

'Foster, Edward J. "Evolutionary or Super Audio Revolutionary? Audio, Nov 1999, page 40-47.

This is a Sony demo of SACD. Unfortunately they were caught cheating...
"When I pushed the point, the engineer admitted to adding a bit of reverb and otherwise toying around to make the sound 'more natural.'' - mtrycrafts

I would hardly call this a scientific way of dismissing SACD. Does this book have anything more substantive?


This is not a book. An article written by Foster about a Sony attempt to demonstrate the SACD vs CD. That sentence is a sample from that demonstration. It is telling that Sony had to cheat to demonstrate SACD.

http://www.stereophile.com//features/374/index.html

Another article on SACD and its technical problems.

If you are looking for science papers you better dismiss that Sony as well; it isn't scientific anymore than the articles posted. You won't find one. No one wants to do a credible DBT of the two. Might give the wrong answer.

[Buckle-meister]

In all likelihood your loudspeakers are almost always the weakest component.

No, 99.9% of the time the room itself will almost certainly be the weakest component. I understand why they don't, but people need to get into their head that the room is part of the hi-fi, not just an entity 'the hi-fi' is placed in.

[tbewick]

hi mtrycrafts,

Thanks for the link. It's very technical (and way above my head) but does not present audibility tests. Are these available in the referenced papers? I find this utterly perplexing. If you were to read a medical journal on drugs testing, the author would not state that drug X is better than drug Y and then move on smoothly. They would either provide data supporting this claim in the paper itself, or they would provide a reference where such data is available. They would view experimental testing with the same importance as the theoretical description of how the drug works. Otherwise the theoretical model would be useless. In fact, the experimental data is far more important than the theory itself.

The books I read on CD digital audio state that it is 'transparent' or quote the low harmonic distortion and high dynamic range/signal-to-noise figures (the Sony textbook which talks-up SACD does state the case for CD as well). As I asked Chris, are these the only measures of performance you need (THD, s/n, dynamic range, frequency response)?They also say that filter and ADC/DAC design are technically difficult. If so, I would appreciate references explaining how these tests are useful and reliable measures of real-world performance. As is implied in the Stereophile link you gave, one book states in no uncertain terms that the THD spec (sinusoid) test does not reveal all the possible distortion which may be added during ADC/DAC. As most CD players have very good specs, why do authors concentrate attention on how DAC and filter designs produce different results (e.g. some external DAC's producing worse performance)? The only data I've seen is the one Chris posted on jitter audibility.

'if you are looking for science papers you better dismiss that Sony as well; it isn't scientific anymore than the articles posted. You won't find one. No one wants to do a credible DBT of the two. Might give the wrong answer.'

Why, are Sony going to put them under house-arrest? If this is true, then hi-fi must be stuck in the Dark Ages.

[tbewick]

Hi Robbie,

I absolutely agree. Unfortunately though most of us have to share the usage of the living room, which makes installing ugly acoustical treatment problematic. It's much easier to buy a nice new set of speakers.

As I'm sure you know, you can, to some extent, avoid acoustical problems by sitting nearer to the speakers. This was suggested in one of Audioholics THX articles on acoustics. It was reported that for the average living room, you have to sit around 6 feet away from the speakers. This is in order to meet the THX guideline for proportionally hearing the room acoustics and the original, (hopefully uncoloured) speaker sound.

[WmAx]

Does this mean that two 16 bit systems with identical S/N and dynamic range will be audibly identical? I would like references to papers or books which prove this.

The bit depth refers to the SNR. The noise is identical to steady state white noise(just like analog sourced noise).What is there is to prove regarding the digital noise? A properly dithered digital system will have noise identical to an analog circuit. Therefor the audibility of such is a matter of general SNR thresholds; not some specific digital noise.

One of the claims of the Sony textbook is something to do with SACD versus CD and the need for D/A converters:

'the need for high-precision D/A converter circuitry versus the possiblity to even replace D/A circuitry by simple low-pass filtering'

Sony is perhaps one of the least credible sources for information. Realize that any excuse they give is going to be centered around what can make their product appear to be superior. PCM is a highly refined technology. All considerations for proper design have been well known for some time. It might sound complex when you read about it, but it's such routine today, that one can buy an essentially technically perfect performing ADC/DAC PCM system for a computer for $200(E-MU 1212M PCI Card). Transparent audio performance does not require near the performance offered by this example device; it's given as example simply for it's low price in relation to the superb technical performance that is basicly at the limits of possibility, including both ADC and DAC.

I don't know enough about CD to comment on these claims, that was the point of my earlier question - do you know of any papers or books that have measured (understandable) data on digital audio performance?

You have to be very specific. Each parameter is treated as an individual subject. If you want measured final performance, Stereophile is fine for that. The papers discussing ADC/DAC design will refer to theoretical technical limits and considerations, and will not usually refer to perceptual studies. You have to coorelate technical performance with perceptual studies in a seperate step.


Rather than dismissive remarks about SACD, I'm looking for proper tests comparing it to CD.

If you find such a test, let me know. I don't know of a single valid comparison. I am aware of rumors of half-baked tests that do not use a scientific protocol; but these are not reliable tests.

When CD came about; it was developed from scientificly valid perceptual tests that examined the relevant parameters to human audibility. When SACD came about, it was not based upon such testing.

-Chris

[Buckle-meister]

Unfortunately...most of us have to share the usage of the living room...

Simple; chuck them out! :eek: ;) :D

[WmAx]

As I asked Chris, are these the only measures of performance you need (THD, s/n, dynamic range, frequency response)?

Harmonic distortion should be analyzed seperately, not as a total value, unless that total value is known to be a typical spectral distribution. It's important to point this out becuase the THD number can be very low, and distortion can be audible, if it's distributed into unusually high levels into very high harmonics. This will not normally be an issue; but if equipment is defective, or very badly designed(refer to some exotic high-end gear). Also, IMD should be tested at narrow widths, at many individual points at high frequency limitations of the digital system in order to examine technical performance related to the anti-alias filter and the resample system used. Jitter is also of relevance, but will almost always be well under known audibility thresholds. If one really want to nitpick, the clock frequency of a particulare device should be measured if one suspects slight pitch change; as the system could be defective(out of tolerance parts). This should almost never happen, but it's a possibility.

-Chris

[tbewick]

Simple; chuck them out! :eek: ;) :D

I have:D

The papers discussing ADC/DAC design will refer to theoretical technical limits and considerations, and will not usually refer to perceptual studies. You have to coorelate technical performance with perceptual studies in a seperate step.

Thanks for your reply Chris.

To me, this seems an odd way of going about things. I would have thought that once Sony/Panasonic/Philips etc. had developed digital equipment that is audibly transparent, they would stop further research. When Intel design a new CPU, it runs faster. When a new CD player is released, it does what exactly? It's like re-inventing the wheel.

Harmonic distortion should be analyzed seperately, not as a total value, unless that total value is known to be a typical spectral distribution. It's important to point this out becuase the THD number can be very low, and distortion can be audible, if it's distributed into unusually high levels into very high harmonics. This will not normally be an issue; but if equipment is defective, or very badly designed(refer to some exotic high-end gear). Also, IMD should be tested at narrow widths, at many individual points at high frequency limitations of the digital system in order to examine technical performance related to the anti-alias filter and the resample system used. Jitter is also of relevance, but will almost always be well under known audibility thresholds. If one really want to nitpick, the clock frequency of a particulare device should be measured if one suspects slight pitch change; as the system could be defective(out of tolerance parts). This should almost never happen, but it's a possibility.

I'll look out for these specs in the future reviews. I've only ever seen harmonic distortion specs presented like this for high-end loudspeakers.

I might do some further reading on this subject. Principles of Digital Audio by Pohlmann is meant to be good, but it'll probably be incomprehensible.

[mtrycrafts]

[QUOTE=tbewick]
To me, this seems an odd way of going about things. I would have thought that once Sony/Panasonic/Philips etc. had developed digital equipment that is audibly transparent, they would stop further research.

Well, this is a marketplace where something new sells, no matter if there is an added benefit or not. Would you want last years body in next years cars?

When Intel design a new CPU, it runs faster.

Yes, in the lab. Will you notice it typing faster? Your server allow you faster up/down loads to take advantage? Not to say when you have huge number crunching to do, it will be faster and maybe noticeable. I haven't noticed much in my comp upgrade.:D

When a new CD player is released, it does what exactly? It's like re-inventing the wheel.

Yes, that is what it is. Will audiophiles stand for last years CD player? With no improvement on it, even if it is only psychological? No, the public is well conditioned to buying the latest and greatest, no matter what. How else would the marketplace expand? If you don't replace but once every 10 years, how many can they sell? Market saturation and stagnation sets in pretty quick. :D


I might do some further reading on this subject. Principles of Digital Audio by Pohlmann is meant to be good, but it'll probably be incomprehensible.

Some parts will be, lots of it is understandable.

[mtrycrafts]

hi mtrycrafts,

Thanks for the link. It's very technical (and way above my head) but does not present audibility tests. Are these available in the referenced papers? I find this utterly perplexing. If you were to read a medical journal on drugs testing, the author would not state that drug X is better than drug Y and then move on smoothly. They would either provide data supporting this claim in the paper itself, or they would provide a reference where such data is available. They would view experimental testing with the same importance as the theoretical description of how the drug works. Otherwise the theoretical model would be useless. In fact, the experimental data is far more important than the theory itself.

.

Its like this in audio. It is about selling a product. Since it is not deadly as medications can be, the FTC, FCC, whoever regulates has set only basic limits, amp power ratings. In medicine, the Food and Drug agency regulates pretty well, at times as we see some drugs are recalled by them, from time to time. Not all Journal research are created equal. One only has to look at some of the Journal stuff that came out of Harvard on the effects of prayer. It was even fraudulent. But, that is off topic:D

Back to audio. If the industry used DBT listening to compare components, I'd be in fat city and out of here:D There would not be an audio market you would recognize:D That would be the only meaningful testing and is not conducted for an obvious reason, to me at least:D

So, I don't know, other than to pull out other documents on audibility, threshold of detection and see if what that article found would be audible.

He could have just gone straight to the DBT comparison with no technical investigation other than the set up and testing procedures.
I don't have a good answer for you. It isn't quite like medicine.