You were burning the midnight oil last night! (But you seem to get grumpier as the night wears on!)
Yes, I was trying to be gracious in response to Pluto's reply but I didn't the opportunity to reply to your message as it was my bedtime.
DBX was more precisely known as a "Compander" operating in similar manner to Dolby A/B. (Pluto mentioned Dolby first not I...)
The essence of what I'm saying, and the driving force behind my convictions is preservation of a musical heritage. To me, throwing out a Vinyl album is like trashing the Mona Lisa then replacing it with a poorly scanned Bitmap. Would you discard the Mona Lisa unless you had to ???
Lets make my position on CD clearer....
- I can have strong convictions about the superiority of vinyl without denying some of the advantages of CD. Certain new music is ONLY available on CD. It's a seller's market, that's why I can still recommend CD since that is commonly available. There's no point in recommending The Doors 180g vinyl specifically to someone who doesn't have a turntable! But I can encourage those who still possess vinyl to rediscover it.
- CD is a soon to be obsolete medium while Vinyl is still in manufacture at Sony, Warner Bros etc more than 20 yrs after it's planned demise. Bottom line : both are going to end up obsolete but will CD in it's current form still be produced in 2028 ? I have a dvd collection since 1998 of 4-500 discs. In light of new developments I could bin these now, less than 10 years later. Why? Because the new digital stuff is better ? Why? Because the older digital stuff is worse. Vinyl has survived the test of time...
- Visit any recent hifi show and you will see maximum interest in Vinyl. (Illustrated by the sheer number of turntables available for demo)
- CD is a flawed medium, brilliantly flawed but flawed nevertheless (or why try to replace it with HDCD, SACD, DVDaudio, 24 bit 96Kz, High Def formats etc.). There simply aren't enough bits on a standard CD to realistically present a rapidly varying amplitude analogue complexor for 0.75 - 1 hour. This resolution problem is being addressed by appearance of higher volume memory (something that wasn't available back then so they had to go with what they had) and new formats. Buyers believed what Philips marketing WANTED them to believe. While the Creators have been quietly moving the goalposts, everyone seems strangely forgiving...
- CD WILL be replaced by a higher definition format (if not SACD then something else). Vinyl is ALREADY a high definition format. If I sat any member of the public down in front of my system A-B-ing these 2 replay methods it would take them less than 10 seconds to prefer vinyl ("Warm sound" would not be the reason given either...).
- Vinyl DOES have it's LF limitations - it DOESN'T go down to DC (neither does CD by choice!) and just as well (!!) otherwise all of our loudspeakers would be blown by now. The steady state current alone would cause voice coil overheating. Besides if that were the sole criterion for music reproduction no-one would have bought a pair of ESL-57s without a subwoofer. 2-Channel music requires a different philosophy from Home Cinema and even then subwoofers typically bottom out at 15-20 HZ. (Even very low frequencies are seen as "virtual DC".)
In conclusion Vinyl is viable and usable, and for me, superior to listen to like I always said.
Not personally. While dbx was capable of impressive quantities of NR, it was far more audible in operation than Dolby A. Fundamentally this is because Dolby A operated in four discrete bands so, for instance, an orchestral bass drum would not modulate the higher frequency components of tape hiss. dbx was a wideband system and thus very prone to this kind of problem. From a technical standpoint, Dolby (A or B) required accurate gain setting of the tape machine (<1dB) due to its non-linear operating characteristics. Dolby relied upon this very accurate line-up to ensure that it operated in a exactly complementary manner on replay. dbx was essentially a linear 2:1 compander and therefore a lot less fussy about line up.
For most in the industry at that time, the 10-15dB NR of Dolby A with few side-effects was preferred to the more impressive, but frequently audible NR operation of dbx. Another flaw with dbx became apparent when working tracks as stereo pairs – the audibility of the operation could be different on each of the two tracks, and this could cause some very disturbing stereo image anomalies.
Dolby A became more or less ubiquitous. Had dbx arrived before Dolby, the situation might have been reversed but take up of dbx would always have been limited by its greater audibility of operation. Dolby A, I believe, is one of the most significant inventions of the late twentieth century.
Bill said, "One thing that rankles (not just me but a common criticism) is the tendency to cram into the top 2dB"
Agreed. Blame the US record companies who really do believe that loud is good. This thinking took its rise when medium wave was king. The nature of AM broadcast is such that louder = greater coverage area = greater exposure of the advertising. The cutting of vinyl masters to the highest possible level had long been a holy grail of the record business but this, perhaps, was due to the fact that vinyl was inherently a nasty, noisy medium. N.B. everybody in the industry was conscious of the fact that gramophone records sounded poor compared to the studio tapes from which they were derived.
The original intention with CD was to use the upper 10dB to accommodate 'occasional transients'. The recommended maximum average level, according to the Red Book, should be about -10dBFS with the remainder being available for extra dynamic thrills (my words). Now if you are making a boring record without any dynamic thrills, do you restrict it to -10dBFS or modulate the medium as hard as you possibly can?
There simply aren't enough bits on a standard CD to realistically present a rapidly varying amplitude analogue complexor for 0.75 - 1 hour
I think I would dispute that. Were you within easy reach of London I would lay the following challenge: that I come round with some simplistic mastering kit, and make a CD from the output of your turntable (or more accurately, the output of your RIAA amplifier). We would then play that CD back on my modest player (you have claimed that Mrs Colborne can detect a change in the sound of yours by placing a table mat upon it - that makes it faulty in my book) and see if you can distinguish the result from the vinyl.
Pluto, thanks for your kind feedback on noise reduction.
"you have claimed that Mrs Colborne can detect a change in the sound of yours by placing a table mat upon it "
Not claimed...proved in a blind test.
..and no I do not think that my CD player is either faulty or exceptional.
"Ripping" vinyl is something I've never tried actually (seemed like sacrilege) otherwise I could offer an opinion on it's capability. For a start if I'm unimpressed by a ("perfect") CD transcription from the master, bought in a shop, I'm even less likely to be impressed by yours!
"Spot on Bill. I really can't understand those that have chucked away all their vinyl. I think that over use of the rose coloured glasses when talking about vinyl is a bit too common though because in my experience there are very many poor quality pressings, many even off centre so badly that they wow noticeably and some so overcut that they distort on sibilants on whatever equipment you use. I blame joe public for not rejecting them. A friend on mine owned a record shop and had a batch of Rod Stewart's Sailing album (ugh) that were so off centre they sounded awful. It was a big seller so not having time to order more he sold them expecting to get a few back. Not one was returned.
You're right about CDs, too many are pointlessly becoming more and more compressed and louder and louder. Why????? "
Fred, sincere apologies my friend, this page had rolled over before I discovered you had popped a message in at the end. Thank you for your kind remark. Yes, one of the worst offenders I've seen was the HIFi News/RR test disc (so badly off centre it could have been re-drilled!)
if I'm unimpressed by a ("perfect") CD transcription from the master, bought in a shop, I'm even less likely to be impressed by yours!
Whoever claimed that commercial CD transcriptions are pefect copies of the master? You have already observed yourself that modern CD mastering appears to have gone somewhat off the rails; there is no general logical conclusion to be drawn from this regarding the potential of the 16bit medium to be transparent or otherwise.
"Whoever claimed that commercial CD transcriptions are perfect copies of the master?
Are you referring to the recording (delivered to the CD mastering facility by the studio) or the copies of the CD master (bulk duplicated by the factory)? The terminology is ambiguous. Are we talking about the input to the mastering facility or the output from?
Yes, I am happy that the manufacturing process is sufficiently good that the manufactured discs are sufficiently close to the master delivered to the factory – there are sometimes problems but they are rare these days. DVDs are far more demanding and the factories have got these good enough. CDs, by comparison, are a doddle.
No, I am not happy with the subjective results produced by many mastering operations. It is here that significant damage is sometimes done - the levels thing, for instance. As I said earlier, after 25 years of CD there are still mastering facilities that aren't coping with their loss of industry "clout" compared to the vinyl days. Over zealous mastering frequently does more harm than good.
I am confident that I could create a 16 bit digital rip from your gramophone that would be indistinguishable from the real thing. I am equally confident that I can create a red book CD from that 16 bit data, equally indistinguishable.
To John Fisher, Of course, Physics has given rise to much of what we enjoy as part of our comfortable modern day life. Imagine, how we would feel if we didn't have electricity any more! So, hopefully, you would campaign hard that Physics and other scientific research is fully funded out of taxpayers' money
Problem comes when WE try to explain the more subtle effects of a physical system. We can understand broadly how a system works, enough to satisfy the criterion needed to make it into a working solution. But, like many physical systems, if you want to get as good a performance as you can out of the system, one may need to tune the system experimentally, rather than just through a theoretical physics solution.
For a research physicist, it's when we find a phenomenon that we can't explain that it becomes really interesting, such as happened in the discovery of the neutrino and the discovery of strange particles!
Coming back to the subject of hi-fi tweaks, by the fact they are 'tweaks' implies that we are dealing with very subtle effects. I'm sure it can be shown using sensitive scientific instruments whether or not a particular tweak has had an affect on the sound reaching a listener. The question is whether the listener can himself hear it. If he can, then maybe he can benefit from it. If not, then why should he be worried about it?
To Pluto, Thanks for the more detailed explanation about error correction on CDs. However, an error correction is still an error correction. There is also a general law that once knowledge is lost it cannot be recovered without returning to the original source. For John Fisher, it's known as the Second Law of Thermodynamics. The lost of knowledge means an increase of entropy.
It was also my hope that digital data would not be corrupted in data transfer. But, I'm afraid that was to be dashed when I tried copying CDs from a 'Master CD'. Both my wife and myself hear it, and we have spent frustrating hours deciding on which copies gave good results. Indeed, if you can't hear any difference, then you're lucky. Life would then be so much simpler
Another point after using Isotek disc and magnetic mat the initial read time was more than half of the time it took prior to using them - even on discs that previously gave me trouble loading - surely this is a plus - most of the time the optic now shows info without any chirping - surely this shows that optic is reading more accurately. ....Carl.
To Dick Fong, a point you appear to miss about 'error correction' is that it comes in many forms, now back in the days of early computer interfaces it took the form of 'parity bit' checking, that told you simply that an error had occured. Many years later 'error correction' took on a whole new meaning, and that was 'lossless correction', a bit like zip file compression every byte can be recreated, unlike JPG compression that does a good job but cannot recreate the original identically.
Now in a similar way Solomen Reed error correction doe not try and make a guess, or fill the gaps, no it takes a 'pre noted' code and from that can recreate the exact byte, not a near copy, but recreate the exact image of what was there, so it is not so much 'correction' as having spare capacity to fully put right any error, hence the recovered bit stream is exactly the same as was on the original, hence it is completely transparent to the user. Solomen Reed codes are extreamly mathamatical and I don't pretend to understand them but I do understand the principles of 'lossless' correction, by lossless I do mean nothing is lost. So we do recover every byte as intended - exactly and correctly.
To Carl, I do not understant your expression 'chirping', and how on earth can a optical read device be affected by a non magnetic disc? As I said previously if the error correction can basically remove all errors then what is 'accuracy', no digital system reads discs inaccurately otherwise your computer programs would not work, a large part of the CD's succsess is that it does work and every time, in a computer situation or an audio playback situation, it does work and very reliably at that. Surly that would not be so if one had to 'demag' a disc before using it, I bet you never 'demaged' a computer disc before installing it, now these two are a similar standard, if the computer disc had many 'inaccuracies' then I would understand your worries with the audio disc, but they don't.
So what is this 'chirping' and what are the 'inaccuracies' you mention?
To Pluto, Thanks for the more detailed explanation about error correction on CDs. However, an error correction is still an error correction. There is also a general law that once knowledge is lost it cannot be recovered without returning to the original source....The lost of knowledge means an increase of entropy.
Dick - there is no magic involved in error correction, nor anything in defiance of the laws which govern entropy in a system. Error correction has a significant overhead. I don't recall the exact figures for CD but, for argument's sake, there might be 10% extra data recorded on a disc which, most of the time, remains entirely unused. Only when an error condition arises is it brought into use, at which time the additional data is utilised to recover the original data. Anybody who stores data on CD-ROM makes extensive practical use of error correction and you know what? They don't even realise they're doing it.
ALL modern digital storage systems work like this; it is far more efficient to assume a reasonable error level and allow for it, than to design a system for perfection. Your hard disk uses a coding scheme known as PRML which is a statistical best guess system, backed up by powerful error correction. When was the last time your hard disk replayed some data wrongly?
Good point Pluto, but back to the vinyl issue, lets get some facts right, a vinyl system does not have infinite resolution, is has noise at the bottom and distortion at the top, it is not capabal of very low frequencies and it distorts badly at high frequencies, tracking distortion etc. Note also the vinyl system is a development of the cylinder player whereas the CD is a designed solution, designed from the ground up to be a superior playback system. For most of the world and for most users they achieved it, however in all walks of life one may encounter the 'diehard', the guy stating that his 1950 Woolsey car is better than anything, that is humane nature.
The cylinder died a death, the 78 followed, and the 33 will follow, I guess a new format will beat all preceding. That is the way progress is, in the same way many still believe SE triodes sound better, but in reality they only have distortion artefacts that sound more pleasing. Note I say 'pleasing' not more accurate, in the same way vinyl has some appealing distortions that sound good, no way is vinyl replay more accurate or more correct but it may seem more appealing.
Re: the Mona Lisa bitmapped copy, if the copy had far higher resolution than the original painting then it would be a perfect and accurate copy. Note also a vinyl pressing is not the original recording, that would be the 15ips master tape or a digital recording, now these originals so few have ever heard that many have no knowledge of what the original actually sounded like.
Recently I had a local artist Michael Toohig paint a Picasso look alike for the kitchen, when I asked him to sign it 'Picasso' he became a bit uncomfortable. But what the hell, how many of us have ever seen an original Picasso, who would know. In the same way I am saying that if you never heard the studio recording then you would never know if your precious vinyl copy was anything like the original. I think it important to realise how little we know for the most part and how easy it is to be duped into untruths, an important part of the salesman’s armoury
Hi, Pluto and John, Thanks for the valiant efforts to explain the theory of error correction. How do you know that the term "lossless" is not some PR of the companies producing the software. When CDs came out it was promised that they would be "perfect". Then they started producing Super Audio CDs, DAT machines sampling at twice the normal frequency, and so it will go on! It would not surprise me to find that engineers are working on an even more perfect means of error correction. Pluto, you give an example where there is, say, 10% extra data that is recorded. But, what happens if the information loss was in the 90% data that is not part of this extra data?
If you are so interested, there is an authoritative essay on "Digital Revolution (Part III) - Error Correction Codes", <http://www.ams.org/featurecolumn/archive/errors1.html>. Indeed, in the references there is a research paper from as recent as 1996 entitled "Near optimum error correcting coding and decoding: Turbo-codes", which would seem to imply that research into error correcting codes is still very much a vibrant area.
Here's another article from Oxford University, <http://www.bodley.ox.ac.uk/dept/preservation/information/audiovisual/nara/nara.htm> It's clear there that the error correction software works to some limiting tolerance, i.e., it is not absolutely perfect: "Optical systems typically provide a statistical probability of error of only one byte out of every one billion bytes", quoting from the article. I wonder what then is the statistical probability of error for typical consumer CD production.
In the end, it's what I've said, "the proof of the pudding is in the eating". Unfortunately, our experience is that we actually hear differences in the CD copies we have made. I wasn't expecting this and I fervently wish it weren't so. Our interest is in classical music and my wish is to reproduce music as close to what we hear in the concert hall as we can. The experience may be different in pop music, for example. Especially, if an important element of the music is the electronic enhancement that seems often to be used.
OK Dick, appreciate the in depth reply so point by point:
Lossless compression was not dreamt up by any PR person, is is a well known expression in software circles. Now the 'Ploughmans Lunch' that was a total marketing ploy created by Watney's back in the 60s.
When CD came out it did appear relatively perfect, only after a time did some areas of playback came into question, improvements with D/A conversion etc. did improve results enormously, so the recording spec. was pretty much there anyway.
DAT machines came before Super Audio CD, and did sample at a slightly faster rate (48KHz), but not double.
Yes engineers are working on new compression methods all the time, as these are 'the holy grail' of software, but 'red book' CD is not compressed at all, only error corrected, now MP3 is a compression system and often sounds like it, but remember CD was designed to be a 'step up' from vinyl at the time and to 95% of users it was.
To understand Pluto's input here you need to understand Soloman Reed correction far more than you seem to do, it is very mathematical!
No comment on the references made here, but I will check them out soon.
However the quote an'error of only one byte out of every one billion bytes' well that works out to about eight errors per complete CD playback, not allot IMO.
OK re the last paragraph, I can't understand it either, but sometimes there are other subtle changes occurring that one attributes to the copying process but are not actually part of it. This sort of missed input is very common in pure research, it happens all the time.
Be it classical or other a difference heard is a difference, the questions are only why and are these differences repeatable and conclusive, and if so then something needs to be addressed.
John...
PS I am not out to 'knock' anyone here, but only to understand, and maybe to understand why these differences occur, more through theoretical interest than anything.
Thanks, John, for the email. It would be lovely to understand exactly why these differences occur, but life is too short, even for one mathematically inclined, unless that is your field. I'm already having trouble finding time listening to my collection of CDs! So, one guesses until someone who has looked into it extensively comes up with the facts.
As to error corrections, from my quick perusal, there seems to be a number of algorithms out there that people are researching into. Certainly, having an 'error of only one byte out of every one billion bytes' sounds pretty good. But, I'm not sure that for a consumer product such as an audio CD it is as good as that. One of the marvels of Nature is what amazing instruments the human eye and the human ear are. But, that has its downside, and that is, they can be extremely discerning and able to detect extraordinarily subtle effects! Unfortunately, when the CD was brought out, it was defined as a consumer product and not as a high-fidelity one. Thus, the quality constraints were kept as low as possible, as, of course, that made them easier to manufacture. So, a sampling frequency of just 44.1 kHz was chosen. However, manufacturers of CD players and DACs have so refined their equipment that real hi-fi quality can be obtained from a CD. Although, I think it still can't compete with the best that you can get from vinyl. Still, CDs can give that rich, live, visceral quality of a real performance, which with their convenience, makes them my medium of choice, and, I believe, at less cost than getting a more superlative performance from vinyl than from the CD.
BTW, Pioneer, for one, did bring out a DAT recorder that could record at 96 kHz. It was highly praised at the time, with a marked improvement over normal DAT recording at 48 kHz. I don't know if anybody else did too.
And now we are also getting CDs proudly labeled as being remastered at 96 kHz in 24-bit digital stereo! What were we getting before and can we hear the difference? I think we can hear the difference and that to me shows that it may not be surprising if copying a CD at 44.1 kHz in 16-bit mode is not the perfect process we might once have hoped it to be.
Dick – you appear to be confusing the marketing department's use of the term 'perfect' with the mathematician's. The advertising slogan "perfect sound forever" should indeed be taken with a pinch of cascara, but when I say that a CD player in good health playing a disc that's not too grubby reproduces the data on the disc with 100% accuracy, I mean it. You may not like the sound that issues forth from your player, but that's your problem.
As I have asked before, when was the last time the CD-ROM in your computer declared an error? Or the hard disk? Chances are you have never experienced either phenomenon. Do you doubt the data integrity of these media with the same lack of faith you reserve for Red Book audio? While it is a fact that there is less error protection on Red Book (audio) discs than Yellow Book (CD-ROM) discs, the Red Book standard still offers sufficient protection for discs in half decent condition. Furthermore there is a fairly small gap between interpolation and muting so if your player is having difficulties you are left in no doubt that something is amiss.
I find it odd that more players are not equipped with data health indicators. It only takes 3 LEDs – solid green, full data retrieval. Flashing green, correcting (NB with 100% recovery). Yellow, interpolating (guessing) and red, muting. If you did have such an indicator, you would observe that for about 55 seconds in every minute the green LED would flash in between the occasional solid burst.
Your question
what happens if the information loss was in the 90% data that is not part of this extra data?
does not make complete sense I'm afraid but I'll interpolate what you mean. The structure of a disc is not one where the ECC data are stored in a different area to the active data. The whole lot is stored together in a complex interwoven arrangement. This in turn is spread over a large distance in order to minimise the damage caused by one physical corruption such as a speck of dust. It is for this reason that we are told to clean our CDs in a radial, not circular, movement.If you are going to cause damage by cleaning, the system is inherently more resistant to radial damage than damage that follows the helical pattern of the data channel. Once the data are read off disc, everything is loaded into a matrix which has the property of being able to determine the accuracy of the data it contains, and within the constraints of the system, making necessary corrections. The entire data structure is thus self-supporting until the error correction runs out of steam which, I assure you, is a rare occurrence unless your discs and/or player are in truly bad condition.
I cannot determine at a distance why your CD copies sound unlike the originals, but can only surmise that uncorrected errors are creeping in somewhere either because of poor equipment or technique. I can typically make copies of audio CDs with a significantly lower error rate and better jitter levels than the original. However, i really cannot understand your closing comment which implies that you perceive better results with pop music than classical. Clearly you have players that are capable of discriminating between different musical genres and handling them differently. That is impressive.
it may not be surprising if copying a CD at 44.1 kHz in 16-bit mode is not the perfect process we might once have hoped it to be.
Nonsense. By using any number of checksum algorithms it is possible to be sure of a bit-perfect copy. Well, at least to a probability of <the number of grains of sand on the planet> : 1.
The occasional bit or bits in error is not going to affect your enjoyment of an entire symphony. If you find the overall sound of CD unsatisfying there is one thing of which you can be (almost) certain. It is not due to errors, error correction or anything related thereto.
It is most likely that you are simply unaware of what studio output actually sounds like. Truth and pain are frequent travelling companions.
