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Some information/comparisons/clarification wrt vinyl and Redbook CD

Jakob1863

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In another thread i´ve mentioned that the system dynamics figure of a 16 bit / 44.1 kHz (aka Redbook CD, i´ll use the RBCD from here) system would be around 55 - 60 dB and that surprisingly that number would be achieveable with the old vinyl system if best possible practice was followed.

For clarification i want to add that these numbers are calculated on basis of a system overall, including the reproduction system and environmental variables.
That is the reason why i would consider something like 76 dB DR for a vinyl system not as achievable, leaving laser turntables and other optical scanning devices aside.

As the usual measurement records were a limiting factor when measuring low frequency noise components, a mechanically coupling device was introduced (for example by Thorens) directly coupled to the bearing of a turntable do assess the noise ground in silence and when rotating. Usually even measured that way the best turntables were around -70 to -75 dB .
An example measurement and a picture of the coupling device:
http://www.connect.de/testbericht/rumpelspektrum-510086.html

In the graph the red curve represents the measurement record, the blue curve the coupling device result and the black one represents the noise level of the measurement setup in silence.

Additionally i reminded to the high frequency limit of RBCD which vinyl does not have and otoh pointed to the difficulties of vinyl if large out of phase content in the bass region is present.
Although under additional constraints the Nyquist limit for the RBCD is 22.05 kHz the more practical limit was/is 20 kHz.

Otoh we know that already during the development of the CD4 system (quadrophony on vinyl) the rear channels were cut using an ultrasonic carrier and were approaching ~45 - 50 kHz , afair that triggered the invention of the shibata diamond cut.
Of course there is a level limit for these high frequency as the RIAA preequalization curve can´t be extended without above 20 kHz. Again afair level of the rear channels was down at least 15 dB .

Surprisingly high frequency content (also down in level of course) was found on a direct to dics record:

http://www.gammaelectronics.xyz/audio_02-1980_TIM.html

Sheffield Lab drum and test record, cymbal crash
 

Cosmik

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In another thread about the requirements for a transparent recording system, Amir linked to an article that pointed out that meaningful comparisons also depend on the spectra of noise versus the sensitivity of the ear. Raw figures can be misleading without extra information about weighting, noise shaping and so on.
 

March Audio

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Ditto. Not a number I can reconcile?????

Jakob, can you clarify what you mean by "dynamics figure"? You may be meaning something different, but 16 bit dynamic range is 96dB.
 

DonH56

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SNR = 6N + 1.76 so an ideal 16-bit converter actually has nearly 98 dB based on quantization noise (only). Also note that SFDR goes as ~9N so the noise floor is close to 144 dB. The basic math scales the signal as 1/sqrt(2) and quantization noise as 1/sqrt(12). To that must be added all the "normal" noise sources like thermal/Johnson noise, shot noise, flicker noise, etc. and then you add clock feedthrough and other nonlinearities on top of that...
 
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Jakob1863

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To be a bit pedantic :) it is SNR= 6.02 x N + OSF + CF (dB)
with N = number of bits, OSF = oversampling factor and CF = correction factor (signal dependent)

That sums up in case of 16 bit, OSF = 0.44 (44.1 kHz Samplingrate but only 20 kHz signal bandwidth) and CF = 1.7 dB (sinus signal with full scale amplitude)
to the famous SNR = 98,44 dB as theoretical maximum for the ideal quantizer that DonH56 mentioned.

@Cosmik ,

sure, but why did you think that my post was meant as part of a discussion about audible transparent recording systems?
The other thread was closed, so i had no chance for further clarification there.

@Frank Dernie & @BE718 ,

it´s not "dynamic figure" of a pure DA-converter but the "system dynamic" figure which denotes the systems usuable range overall.
In the original post i therefore mentioned (hoping that it would be a sufficient explanation) the avoidance of overload and sufficient distance to environmental noise (although weighted) at the bottom end. In the old day a conservative calculation would have ended at 50 - 55 dB usable system dynamics, but today it is a bit higher ......
 

Cosmik

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Jakob1863 said:
@Cosmik ,

sure, but why did you think that my post was meant as part of a discussion about audible transparent recording systems?
The other thread was closed, so i had no chance for further clarification there.
What I meant was "In another thread (which happened to be about transparent recording systems), Amir linked to an article..."
 

amirm

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it´s not "dynamic figure" of a pure DA-converter but the "system dynamic" figure which denotes the systems usuable range overall.
That number has been studied and it approaches 120 db. Where did you number come from?
 

March Audio

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@Frank Dernie & @BE718 ,

it´s not "dynamic figure" of a pure DA-converter but the "system dynamic" figure which denotes the systems usuable range overall.
In the original post i therefore mentioned (hoping that it would be a sufficient explanation) the avoidance of overload and sufficient distance to environmental noise (although weighted) at the bottom end. In the old day a conservative calculation would have ended at 50 - 55 dB usable system dynamics, but today it is a bit higher ......

Hi Jakob,

My understanding is as Amirs; that with dither and noise shaping the figure is more like 120dB for 16bit. So same question really, where does the 55dB come from? When you say environmental noise, do you mean this is an in room acoustic measurement as opposed to an electrical measurement?

If this is the case then the ultimate limitation is not the source medium, it is the speaker, amplifier and background noise level.

Just for kicks I have just dragged out my B&K slm and measured the background noise level in my listening room. It is a quiet room and it bounced around 25-28 dB(A). The LAeq (in simple terms the exposure average over time of a couple of minutes) was 25.7 dB(A). I havent actually measured the max output of my speakers but being a little conservative I would say about 105dB(A) at 1 m. So thats a potential (acoustic) dynamic range of 80dB.

This of course ignores the fact that few recordings utilize the potential available dynamic range. :)
 
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fas42

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Subjectively, many CD replay systems, and recordings, come across as lacking dynamic range - this is actually an ear/brain interpretation of the distortion artifacts that our hearing systems have to deal with, listening to a type of subtle degradation. The most 'banal' recordings can come to life, replete with great vigour and energy, when this aspect is sorted ... so ... most people can hear "digital distortion" - they just don't realise "what's going on" ...
 

tomelex

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I am not sure but I think Jakob is referring to a system, as in your room noise is already at what, about 35 to 40DB. So you only have so much "usable" range to deal with, you lose 35 to 40 db by just being in an average room with its random noise.
 

Blumlein 88

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I am not sure but I think Jakob is referring to a system, as in your room noise is already at what, about 35 to 40DB. So you only have so much "usable" range to deal with, you lose 35 to 40 db by just being in an average room with its random noise.

I thought this is what Jakob was getting on about here. As Cosmik said above though such a simplistic approach is somewhat misleading. Our ears are going to parse up the band into 30 or so filter banks which allow us to hear some 10db or more into the noise floor. So in the areas of greatest sensitivity 3-5 khz you find many domestic listening rooms are very close to the lower hearing limit, and with our ability to hear into the noise a bit we can get near the lower hearing threshold in those areas. Therefore saying 110 db peaks minus 40 db environmental noise means we only need 70 db dynamic range isn't really accurate. In many homes you can probably hear down to 10 db SPL in that 3-5 khz level, and mediums like tape or LP are going to struggle to be totally silent there.

Now I think the harder end of this is recordings that really exercise 16 bits. A large condenser microphone recording in a hall may well need around 40 db gain. This will get you near the 0 db level in the ADC with a bit of headroom. That microphone preamp may have electrical noise at -120 db, but you added 40 db of gain and now the noise floor is only -80 db. Plus microphones have a bit of self noise above 0 db SPL levels (with one exception I am aware of). So even if recording with 120 db SPL peaks, and a preamp for the microphone of 120 db DNR, the gain and self noise eat into that range. You are probably going to struggle to get more than 75 or 80 db in real range with recordings. However like room noise, noise at a venue and in the recording gear is usually very low in the 3-5 khz range. So in that range the extra bits do help.

That explains why LP and tape at the very best aren't so far off being enough on the SNR front.
 
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Blumlein 88

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Some data related to my above post.

A .9 second silence from a recording in a small church. This was from either a CAD M179 microphone or a Shure KSM 32 (I have the records on another computer). This has a level of -65 db FS. If you amp it up you hear a bit of whoosh of electronic noise with a bit higher level of noise in the church. The gain as I recall was 42 db on the microphone preamp, and provided enough headroom not to clip things. But look at the FFT of that. I used a 128 FFT which has 64 bins so not far off from the 30-32 bins our hearing has. You see in the 4-5 khz range the level is -85 db.
Silence in church FFT.png


Yet even with this level of noise if I look at the level of each sample. Out of 40,000 samples more than 600 are below -100 dbFS. Just short of 2000 samples are below -90 dbFS.
 

Frank Dernie

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@Frank Dernie & @BE718 ,

it´s not "dynamic figure" of a pure DA-converter but the "system dynamic" figure which denotes the systems usuable range overall.
In the original post i therefore mentioned (hoping that it would be a sufficient explanation) the avoidance of overload and sufficient distance to environmental noise (although weighted) at the bottom end. In the old day a conservative calculation would have ended at 50 - 55 dB usable system dynamics, but today it is a bit higher ......
It wasn't a sufficient explanation in the original post. That is why I asked.
It was a woolly speculative figure which is quite wrong in my experience.
When I went from recording on on reel-to-reel tape to DAT (48/16) the useable dynamic range was considerably and obviously wider.

Whether a much wider dynamic range is essential in practice is moot, but the practical dynamic range of 16-bit is way over 60dB
 

Wombat

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The room noise is a factor common to all recorded replaying formats/systems. What we need do with the various recordable media is to compare the maximum recordable dynamic range across the recordable/replay frequencies and relate this to the mediums' base noise levels across those frequencies wrt ambient noise characteristics across those frequencies before we can work out what dynamic range we can hear in our domestic spaces.

It seems to me that a format that has better dynamic range and lower base noise level in the same room conditions will be a better performer, thus. I can't see that vinyl beats Redbook in this regard.
 
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Cosmik

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It wasn't a sufficient explanation in the original post. That is why I asked.
It was a woolly speculative figure which is quite wrong in my experience.
When I went from recording on on reel-to-reel tape to DAT (48/16) the useable dynamic range was considerably and obviously wider.

Whether a much wider dynamic range is essential in practice is moot, but the practical dynamic range of 16-bit is way over 60dB
I don't think I've ever knowingly heard the hiss inherent to the 16 bit digital system... I guess it's there if I turn the volume right up, but usually buried in the ambient/mic noise of most recordings. When I used to use reel-to-reel, however, I was acutely aware of its noise - to the extent of building my own companding noise reduction for it.

A figure of 50-55dB dynamic range would, on the face of it, be about the same as cassette with Dolby B. CD isn't remotely the same.
 
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Jakob1863

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It wasn't a sufficient explanation in the original post. That is why I asked.
It was a woolly speculative figure which is quite wrong in my experience.
When I went from recording on on reel-to-reel tape to DAT (48/16) the useable dynamic range was considerably and obviously wider.

Whether a much wider dynamic range is essential in practice is moot, but the practical dynamic range of 16-bit is way over 60dB

Therefore i said "hoping" , apparently it wasn´t sufficient. :)
Of course it is a bit "woolly" and "speculative" but i´m surprised that nobody else stumbled about it or used a similar figure himself (means among this forum´s members); it´s just applying usual numbers for headroom and footroom.

In the old days it would have been 9 dB for headroom (which today can be lower for various reasons so use around 3 dB) and around 35 dB footroom at the bottom end (considering weigthed number for noise impact).
 
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fas42

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I don't think I've ever knowingly heard the hiss inherent to the 16 bit digital system... I guess it's there if I turn the volume right up, but usually buried in the ambient/mic noise of most recordings. When I used to use reel-to-reel, however, I was acutely aware of its noise - to the extent of building my own companding noise reduction for it.

A figure of 50-55dB dynamic range would, on the face of it, be about the same as cassette with Dolby B. CD isn't remotely the same.
Quite easy to emulate by creating tracks which use a paucity of bits to encode. There are test CDs, I have a Denon one, which has the same musical passage at 0, -20, -40, -60 dB down, with no dithering. The noise is an "electronic" chattering effect, very distinctive - and is almost impossible to hear. That -60 dB version can only be heard clearly with gain at maximum, and one's ear right next to the driver.

A mistake in mastering may make it obvious - I have a CBS CD of female singer opera excerpts, and there is clear digital chattering at the start of the first track - obviously no-one listening too closely at the time, or the boo-boo would have been caught.
 

Cosmik

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Quite easy to emulate by creating tracks which use a paucity of bits to encode. There are test CDs, I have a Denon one, which has the same musical passage at 0, -20, -40, -60 dB down, with no dithering. The noise is an "electronic" chattering effect, very distinctive - and is almost impossible to hear. That -60 dB version can only be heard clearly with gain at maximum, and one's ear right next to the driver.

A mistake in mastering may make it obvious - I have a CBS CD of female singer opera excerpts, and there is clear digital chattering at the start of the first track - obviously no-one listening too closely at the time, or the boo-boo would have been caught.
I wasn't thinking of non-dithered quantisation noise - which certainly would sound horrible if you had the volume high enough, and the music level was low. I was thinking simply of the very, very quiet hiss that dithered 16 bit produces - with noise shaping making it even quieter. And of course, apart from that, the distortion is zero. And yet most audiophiles have been sold the lie that it is a vastly inferior system, so no matter what the reality is, they can never allow themselves to enjoy it.
 
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