[hciman77]

Quote:

Originally Posted by Duggeh /img/forum/go_quote.gif HOORAY for my Uni!

It was my old man's alma mater as well back in the 1950s and one of my favourite sites for visits when I was a TLTP evaluator for the Bionet project back in the mid 1990s and my brother used to fly Tornados out of the local RAF base (Leuchars)...

 

[drarthurwells]

Quote:

Originally Posted by Febs /img/forum/go_quote.gif How is that data can be copied from CD to CD and that the copy can be identical to the original (verifiable by MD5 checksum), and yet audio somehow gets degraded by the copying process? This is quite a paradox, don't you think? Do you have any explanation as to why, in your view, computers are perfectly capable of making bit-perfect copies of data, but not audio?

The material below is excerpted from

http://www.cdrfaq.org/faq04.html#S4-18

Subject: [4-18] Why doesn't the copy of an audio CD sound the same?
(1998/04/06)
There are actually two questions here, so I've split them into separate sections. The most common problem is that the audio extracted to the hard drive doesn't quite match the original.

Subject: [4-18-1] Why doesn't the audio data on the copy match the original?
(1998/04/06)
Most problems are due to poor digital audio extraction from the source media. Some CD-ROM drives will return slightly different data every time an audio track is read. Others, like the Plextor line (e.g. 4Plex, 8Plex, and 12Plex, but not 6Plex) will return the same data every time so long as the source media is clean.

The most fundamental problem is that, if the CD is dirty, the error correction may not be able to correct all of the errors. Some drives will interpolate the missing samples, some won't.

Another problem some CD-ROM drives face is "jitter". See section (2-15) for details.

See also section (3-3) on avoiding clicks in extracted audio, and section (5-5) on which CD-ROM drives are recommended.


Subject: [4-18-2] The audio data matches exactly, why do they sound different?
(2004/12/10)
Suppose you extract the audio track from the copy, and it's an exact binary match of the track you wrote from your hard drive, but the CDs don't sound quite the same. What then?

Most people don't notice any difference between originals and duplicates. Some people notice subtle differences, some people notice huge differences; on better CD players, the differences are harder to hear. Some say CD-R is better, some say worse. While it's true that "bits are bits", there *are* reasons why CD-Rs may sound different even when the data matches exactly.

An excellent paper on the subject is "The Numerically-Identical CD Mystery: A Study in Perception versus Measurement" by Ian Dennis, Julian Dunn, and Doug Carson, submitted to the Audio Engineering Society (Preprint 4339, 101st AES convention). It's available for download in PDF form at http://www.prismsound.com/m_r_downloads/cdinvest.pdf. The paper is primarily concerned with why pressed CDs created at different plants or with different methods sound different, but the observations are relevant to CD-R as well.

The conclusions in the paper suggest that low-frequency modulations in the disc affect the servo and motor electronics, causing distortion noticeable to a critical listener.


One prominent theory is jitter. This isn't the DAE "jitter" described in section (2-15), but rather a timebase error. A good overview can be found in the jitter article on http://www.digido.com/. A brief explanation follows.

The digital-to-analog ("D/A") conversion at the output of the CD player is driven by a clock in the CD player. The clock is tied into feedback mechanisms that keep the disc spinning at the proper speed. If the digital signal being read from the disc has irregular timing, small errors can be induced in the output clock. Even if the CD player gets all of the digital bits accurately, it will produce inferior results if the timing of the bits on the disc isn't precise. Put another way, something has to send a sample to the speakers 44100 times per second, and if it's speeding up and slowing down many times each second your ears are going to notice.

There is some question as to whether the clock driving the output will actually be affected by the input. If the output clock in the CD player is isolated and stable, jitter from the CD will not affect it.

If you play a CD digitally (e.g. by ripping it and then playing it through a sound card), the quality of the CD doesn't matter, because it's the timing of the clock in the sound card that drives the D/A conversion.

It has been asserted that the clocking of bits on a CD-R isn't as precise as on a pressed CD. Writing at different speeds on different types of media requires adjustments to the "write strategy" (section (3-31)) that can result in individual "marks" being sloppier than at other speeds. This could account for inferior -- or at least different -- sound.

Yamaha believes they have found a partial solution for jitter problems with their Audio Master Quality feature. See section (2-41).

 

[chesebert]

Quote:

Originally Posted by drarthurwells /img/forum/go_quote.gif Subject: [4-18] Why doesn't the copy of an audio CD sound the same? (1998/04/06) There are actually two questions here, so I've split them into separate sections. The most common problem is that the audio extracted to the hard drive doesn't quite match the original. Subject: [4-18-1] Why doesn't the audio data on the copy match the original? (1998/04/06) Most problems are due to poor digital audio extraction from the source media. Some CD-ROM drives will return slightly different data every time an audio track is read. Others, like the Plextor line (e.g. 4Plex, 8Plex, and 12Plex, but not 6Plex) will return the same data every time so long as the source media is clean. The most fundamental problem is that, if the CD is dirty, the error correction may not be able to correct all of the errors. Some drives will interpolate the missing samples, some won't. Another problem some CD-ROM drives face is "jitter". See section (2-15) for details. See also section (3-3) on avoiding clicks in extracted audio, and section (5-5) on which CD-ROM drives are recommended. The material below is excerpted from http://www.cdrfaq.org/faq04.html#S4-18 Subject: [4-18-2] The audio data matches exactly, why do they sound different? (2004/12/10) Suppose you extract the audio track from the copy, and it's an exact binary match of the track you wrote from your hard drive, but the CDs don't sound quite the same. What then? Most people don't notice any difference between originals and duplicates. Some people notice subtle differences, some people notice huge differences; on better CD players, the differences are harder to hear. Some say CD-R is better, some say worse. While it's true that "bits are bits", there *are* reasons why CD-Rs may sound different even when the data matches exactly. An excellent paper on the subject is "The Numerically-Identical CD Mystery: A Study in Perception versus Measurement" by Ian Dennis, Julian Dunn, and Doug Carson, submitted to the Audio Engineering Society (Preprint 4339, 101st AES convention). It's available for download in PDF form at http://www.prismsound.com/m_r_downloads/cdinvest.pdf. The paper is primarily concerned with why pressed CDs created at different plants or with different methods sound different, but the observations are relevant to CD-R as well. The conclusions in the paper suggest that low-frequency modulations in the disc affect the servo and motor electronics, causing distortion noticeable to a critical listener. One prominent theory is jitter. This isn't the DAE "jitter" described in section (2-15), but rather a timebase error. A good overview can be found in the jitter article on http://www.digido.com/. A brief explanation follows. The digital-to-analog ("D/A") conversion at the output of the CD player is driven by a clock in the CD player. The clock is tied into feedback mechanisms that keep the disc spinning at the proper speed. If the digital signal being read from the disc has irregular timing, small errors can be induced in the output clock. Even if the CD player gets all of the digital bits accurately, it will produce inferior results if the timing of the bits on the disc isn't precise. Put another way, something has to send a sample to the speakers 44100 times per second, and if it's speeding up and slowing down many times each second your ears are going to notice. There is some question as to whether the clock driving the output will actually be affected by the input. If the output clock in the CD player is isolated and stable, jitter from the CD will not affect it. If you play a CD digitally (e.g. by ripping it and then playing it through a sound card), the quality of the CD doesn't matter, because it's the timing of the clock in the sound card that drives the D/A conversion. It has been asserted that the clocking of bits on a CD-R isn't as precise as on a pressed CD. Writing at different speeds on different types of media requires adjustments to the "write strategy" (section (3-31)) that can result in individual "marks" being sloppier than at other speeds. This could account for inferior -- or at least different -- sound. Yamaha believes they have found a partial solution for jitter problems with their Audio Master Quality feature. See section (2-41).

I think you missed the whole thing about error correction. That's what ECC is for. How do you think computer keep all their 1 and 0 accurate, we are talking about mV and even smaller in the ALU and FPU. design one of those is all about error correction.
what do you think happens when you take 1 drive out of a raid 5 config with 3 drives? The damn array still works just fine and if you put a new drive in it rebuild the data from scratch. Same principle with CD, IIRC, every bit (data bit) is accompanied by 7 error correction bits. So what if one or 2 bits gets inverted..big deal. Here is a little more on the CIRC methods

In the CD, two layers of Reed-Solomon coding separated by a 28-way convolutional interleaver yields a scheme called Cross-Interleaved Reed Solomon Coding (CIRC). The first element of a CIRC decoder is a relatively weak inner (32,28) Reed-Solomon code, shortened from a (255,251) code with 8-bit symbols. This code can correct up to 2 byte errors per 32-byte block. More importantly, it flags as erasures any uncorrectable blocks, i.e., blocks with more than 2 byte errors. The decoded 28-byte blocks, with erasure indications, are then spread by the deinterleaver to different blocks of the (28,24) outer code. Thanks to the deinterleaving, an erased 28-byte block from the inner code becomes a single erased byte in each of 28 outer code blocks. The outer code easily corrects this, since it can handle up to 4 such erasures per block.

The result is a CIRC that can completely correct error bursts up to 4000 bits, or about 2.5 mm on the disc surface. This code is so strong that most CD playback errors are almost certainly caused by tracking errors that cause the laser to jump track, not by uncorrectable error bursts.

 

[memepool]

Quote:

Originally Posted by bigshot /img/forum/go_quote.gif That's totally wrong. If you patched a bunch of mike feeds directly into a digital recorder without balancing levels, EQing, adding reverb, or any other signal processing, it would sound like a mess. The secret to good sound is BALANCE. It's good to keep the signal clean, but you don't have to be obsessive about it.

Also it depends an awful lot on what you are recording. If it's a live string quartet in a hall with good acoustics then a pair of crossed mics feeding a recorder directly will sound great whereas any music which requires amplification to start with necessitates some kind of equalisation in the signal chain.

 

[hciman77]

Quote:

Originally Posted by drarthurwells /img/forum/go_quote.gif An excellent paper on the subject is "The Numerically-Identical CD Mystery: A Study in Perception versus Measurement" by Ian Dennis, Julian Dunn, and Doug Carson, submitted to the Audio Engineering Society (Preprint 4339, 101st AES convention). It's available for download in PDF form at http://www.prismsound.com/m_r_downloads/cdinvest.pdf. The paper is primarily concerned with why pressed CDs created at different plants or with different methods sound different, but the observations are relevant to CD-R as well.

Fatally flawed. Non blind listening tests for starters very little concordance betwen results, and in the blind tests the results indicated that golden eared listeners could not detect which was which - though they thought they could do so in sighted tests. Once again showing that sighted tests are really really unreliable.

 

[13D3Mullard]

Quote:

Originally Posted by Meyvn /img/forum/go_quote.gif Vinyl's frequency response will always be short of what digital is capable of; it's in their nature. The argument of quality is not about frequency bandwidth. It's about simple purity of what is recorded. Analog requires no conversion to and from digital, and is not done in the same sense of units that digital is, so its sheer resolution is fundamentally superior; it's arguable that we've come to the point where that fact is negligible, but I personally don't think it is just yet. At any rate, now that digital recording is so popular, obviously that advantage of vinyl is now gone on 99% of modern recordings, but on older recordings, or the few newer ones that are purely analog, it's just going to be superior in resolution, the same way that film is better than HD cam.

I agree with Mevyn's analysis. I am a declared analogue addict, so I am biassed, but there is certainly more low level detail on LP; and this in itself is quite strange, as it has to be extracted from the background 'wouussh' of the surface noise. This limitation on the LP data retrieval process, means that an equalization curve must be applied to the music or other sonic content prior to it being cut onto vinyl, so that in turn the RIAA curve at the pre-pre will return it to its original shape, while reducing background noise and sibilance.
This appears to be well implemented, as the result to my ears is better than CD. In fact I wonder whether something similar should not be tried with digital. A CD player's data retrieval has to contend with the background electronic "wooussh" produced by the large number of electronic components. Upgrading diodes, caps, and the PSU all bring massive improvements, but the last whisper always seems to be missing, due, I suppose, to the low sampling rate of standard CD, which just seems to limit its ability to retrieve low-level information.

On the other hand the actual analogue recording puts no such limit on information retrieval when upgrading the LP system. My latest Garrard plinth seems to have far more resolution than its predecessor : http://www.theanalogdept.com/anthony_hind.htm
The problem with LP is not the recording itself, but the mechanical process in retrieving this information. I mentioned record diamond interface noise, but the play-back system also has to contend with noise feed-back from the motor to the cartridge and acoustical feed-back from the speakers. Lp upgrades are therefore usually mechanical rather than electronic. Although, of course upgrading the prep-pre, in the same way you would want to upgrade the CD player, will also bring enormous benefits.

The resulting well tweaked LP system seems to be superior to CD in capturing all phenomena related to low level detail : capturing the long decay of a piano note (with CD the note suddenly dies), capturing the micro-dynamics of a quiet but fast change, such as the release of a gut string on a lute.
If you listen to a bowed instrument, on a CD, you can hear the note that is played, but you rarely hear the texture of the bowing, so that chamber music always seems superior on LP.
It seems that whatever one does, the low standard sampling rate of CD limits the possibility of extracting low level detail.

Perhaps part of the problem concerns "brain overload" : when the brain has to "work hard", it tends to lose information. Notice that a number of analogue audiophiles prefer mono over stereo. I think that is because stereo is recorded to 'confuse' the brain into believing that the sound image is 3D; but the brain has to work harder to rebuild the stereo image.
A good mono recording, is therefore somehow less tiring to listen to. I think that in a slightly different way, the brain has to work even harder with digital. It is almost as though part of the digital to analogue conversion has to take place in the brain. In fact, it is rather that the brain has to cope with the rather unnatural and slightly grainy result of the digital conversion.

I think most of the basic variants (improvements) proposed for CD players are trying to respond to the obvious superiority of LP over CD.

Some digital engineers thought that the problem stemmed from the difference between the lightening reaction speed of the DAC and the relatively slow reaction of the analogue op-amps that followed.
This could obviously cause a form of distortion, and faster op-amps were added. There was a slight improvement.

Others thought it was simply the number of components in the CD's DAC and analogue chain, so they put in the best components available to limit the presence of electronic noise : ultra-fast diodes, low noise caps and resistors. There was a further slight improvement, but now the greater transparency also revealed more of the digital nasties.

It was obvious that the low sampling rate was involved, and SACD, in the best case, is clearly superior; however, for standard CD, instead of raising the sampling rate, upsampling was used; but this caused all sorts of aliasing problems, and the added detail is somehow far less "natural" than the standard 16 X 4, or even 16 x 2.

The response to this by some audiophile engineers was complete removal of over sampling, "NOS", and the removal of brick-wall filters; but the sound, though more "natural", is even less dynamic and detailed, while the removal of filters lets through a constant ultra-high frequency noise. This may not be audible, but I understand can damage some tweeters.

All these variations were made in comparison to analogue systems, and I think this, in itself, proves that digital engineers acknowledge the superiority of analogue in most areas, at least while the digital recording uses such low sampling rates.

 

[Febs]

Quote:

Originally Posted by drarthurwells /img/forum/go_quote.gif An excellent paper on the subject is "The Numerically-Identical CD Mystery: A Study in Perception versus Measurement" by Ian Dennis, Julian Dunn, and Doug Carson, submitted to the Audio Engineering Society (Preprint 4339, 101st AES convention). It's available for download in PDF form at http://www.prismsound.com/m_r_downloads/cdinvest.pdf. The paper is primarily concerned with why pressed CDs created at different plants or with different methods sound different, but the observations are relevant to CD-R as well. The conclusions in the paper suggest that low-frequency modulations in the disc affect the servo and motor electronics, causing distortion noticeable to a critical listener.

The paper does not reach that conclusion. The paper says that disk-dependent modulations are such that "masking theory suggests that these would be inaudible." The paper says that "the track-position-dependent modulations are generally higher in frequency and amplitude and, as such, may be noticeable to a critical listener." (Emphasis mine.) This is not a "conclusion" of the paper; it is merely unproven speculation that the authors themselves appear to reject. For example, the paper goes on to conclude that:

1. "Listening tests have so far failed to produce convincing evidence for consistent sonic differences among the TD-2 disc sets."
2. "The blind tests, whilst as yet too small in number to be conclusive, suggest that differences may actually be too small to be audible, even amongst expert listeners."

 

[hciman77]

Quote:

Originally Posted by Febs /img/forum/go_quote.gif [*]"The blind tests, whilst as yet too small in number to be conclusive, suggest that differences may actually be too small to be audible, even amongst expert listeners."[/LIST]

Yep, also the blind tests suggest that "experts" who swear blind (pun intended) that they can hear differences actually cannot hear them when deprived of knowledge of what they are listening to, which is entirely what I would have expected.

Not that it matters but this paper was from 1998 when CD-R tech was relatively immature, for instance my 1999 2X burner could not do DAO correctly and my CD copies from that era would not play back on my PCDP if it had anti-skip on...

 

[hciman77]

From the Boston Audio Society...the results of a blind test between an analog signal and the same signal processed through ADC and DAC steps.


The last two trials were bypass tests of the Sony PCM-F1 digital processor. The F1's video output was looped back to the input and the processor was set to a gain of 1.0 and connected to input B. The signal source was an LP made by Meyer and Peter Mitchell of organist James Johnson--the same production whose digital version has been excerpted on the first and second Stereophile test CDs. The LP was made from an analog master, so we really were comparing an analog source directly with an F1-digitized version. The results on the two trials were 9/15 and 7/15; the total was 16/30, 53% correct.

Conclusion (mine): The addition of ADC/DAC steps is transparent, this is the same test that Ivor Tiefenbrun (Linn) failed at many years ago. Showing that quantization does not have the audibly destructive effects it is supposed to have.

 

[noseallinit]

will analog media ever get any better than it already is?

can we say digital media will continue to progress?

 

[drarthurwells]

Quote:

Originally Posted by noseallinit /img/forum/go_quote.gif will analog media ever get any better than it already is? can we say digital media will continue to progress?

The pertinent question is, "Will digital ever be as good as analog in the ways that analog is superior now".

 

[juzmister]

You will never get the tangible feeling of vinyl...I love watching the cartridge bouncing up and down, it's awesome...

 

[hciman77]

Quote:

Originally Posted by drarthurwells /img/forum/go_quote.gif The pertinent question is, "Will digital ever be as good as analog in the ways that analog is superior now".

Arthur, the real question is, will you ever provide the specifications that show that LP has any real world superiority over CD in any pertinent area , that I have repeatedly asked you to provide.

Smarter folks than I (rec.audio.opinion) have demonstrated that LP has (at best) due to its lower SNR a resolution of approximately 10 - 11 bits i.e 2 bits shy of being able to reproduce an 85db dynamic range, which even a 1984 Sony CDP101 would manage easily. Prove me wrong with some numbers. LP is woefully inferior to CD in all measurable parameters , that of course does not stop people liking it, preference and superiority are not the same.

---------------------

Obviously the effective sample rate on analog Vinyl isn't infinite.


This begs the question, what is the effective sample rate of analog
vinyl?


The sampling device for vinyl playback is the stylus, which is
currently often composed of two 0.4 or 0.5 thousandths of an inch
roughly-ball shaped surfaces.
http://www.audioshopper.com/ElexAtelier/ateliercart.htm


These ball-shaped surfaces significantly deform the groove when they
play it. The area they sample is probably about 2 ten-thousandths of
an inch long.


The inner groves of a LP are about 2.25 inches per
http://members.home.net/dhowlett/pre...ist/igdist.htm . The same
reference gives the length of a 1 KHz tone at 2.25 inch playing
radius as 0.008 "


Simple division shows that there are about 40 0.0002" long samples
in a 1 KHz tone on an LP.


In comparison there are 44.1 samples in a 1 KHz tone on a CD.


Now lets compare the precision of the samples.


A LP has an SNR of at best 65 dB. Shannon gives the number of bits
per sample equal to a given SNR as log2(1+SNR)


66 dB corresponds to a SNR of 2000, so LP's SNR so it is equivalent
to log (2000)/log(2) or about 11 bits.


Therefore the amount of information on a LP per channel is equivalent
to 440,000 bits per second while the amount of information on a CD is
equivalent to 705,600 bits per second.


I conclude that CD is the higher resolution media of the two by a
factor of almost 2.

---------------------

 

[noseallinit]

Quote:

Originally Posted by juzmister /img/forum/go_quote.gif You will never get the tangible feeling of vinyl...I love watching the cartridge bouncing up and down, it's awesome...

it's not the medium I get off on but the music itself!

some of the first recordings I had of various alternative music was recorded onto cassette from off an Atlanta college radio station back in the very early 80's. the recordings were far from good ones but the music itself blew me away. I listened to them on a cheap jam box that me friend let me borrow until I got me first descent stereo. NAD, Polk and B&O Turntable. no system has ever replaced those moments I first heard that music on that jam box.

I eventually acquired most of that music on vinyl meself but it was recordings of the vinyl onto cassette that I listened to. I saved and protected me vinyl instead of playing it to death for other recordings to come. vinyl has a limited life span at it's best. why continue to play it and degrade it..

 

[Davesrose]

Since my digital setup is complete, I'm now going to try out vinyl. A TT is on its way, and I tried going to a used record store today (Wax n'Facts!). I bought all of their old guitar recordings! I have a couple on CD, so I'll be able to demo those. I also found a Living Stereo of Julian Bream: an issue that's making it to SACD at the end of this month. I can't wait to get the SACD and try comparing vinyl with SACD. SACD will probably be superior technically, but it will be interesting to see how euphonic vinyl could be. I'm mainly going to try getting old out of print stuff that you can't find digitally: that would be the main advantage of vinyl. I'll have to see how bad the snaps and pops can be!