Are CD copies as good as the original?

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Anonymous

Guest
I have copied several discs recently onto good quality blanks using my laptop and i think they sound just as good as the original. I have only done a comparison check against originals a couple of times but i could not tell the difference on my system. Maybe on a more expensive transparent one you might be able to.
 

Superaintit

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Feb 8, 2009
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manicm:
In my experience, no. And different blank discs give different results as well.

My experience exactly. Short advice to the original poster: go the hard disk/pc/mac route. It's much more convenient and satisfying than copying disc to disc.
 
A

Anonymous

Guest
A bit of a yes and no answer.

Will the copy contain EXACTLY the same data as the original? Probably not in more than most cases.

Will these differences be noticeable? Depends upon the quality of the playback equipment, and how good the listener is at distinguishing fine differences.

I understand it as: When digital data is written to an optical media (DVD/CD), it is not written in so much of a perfect 0 or 1, on or off, yes or no fashion, but is expressed in more an analogue wave.

The pits and land (0's and 1's for arguments sake) do not have perfectly defined boundaries, with perfectly vertical sides. The side is more of a slope, with a bit of a curve in the bottom of the pit, and a curve near the top, where it meets the land.

The reading laser reflection pickup sees these pits and land, and uses a threshold system, whereby it treats a certain deep depth of pit as a 0 and a particular shallow up to land as 1. The slop and most of the curve gets binned, as the reader is only looking for two values 0 or 1, pit or land. The laser reflection pickup receives varying amounts of laser light reflected back, which it sends to a circuit, which switches between 0 and 1 when the output of the pickup reaches/falls below certain thresholds.

Now, if we take a poor quality burner, and poor quality discs, these pits and the edges are going to be badly shaped, which can introduce errors quite off to what the original data was. Whilst a high quality combination may not be perfectly identical to the original in terms of pit depth and wall shape, it may be seen as no different compared with the original when read with an optical drive.

Of course, when one uses a computer to check the data, software can perform comparisons between the read data multiple times and produce a statistical output indicating the quality of a burn. But there's a big factor and that is the drive one is using in the computer. If the drive has a poor quality laser, poor circuit for determining 0's and 1's or a poor calibration, then who knows if the burn was good or bad?

We have a standalone CD-R (Marantz DR6000) and I use my PC for burning CD-R's, but am keeping the loss less files on the hard disk, encased in archives with error checking. I wonder what the quality of a burn would be like using the digital SPDIF output of the M-Audio 2496 sound card into the DR-6000, compared with a straight 10X burn from the PC's DVD/CD-RW unit - in theory much better, but in practice maybe not?

As for good quality media - both DVD and CD, Taiyo Yuden (Japan) seem to raved about. Verbatim (Japan/Taiwan) also gain praise. There does seem to be a lot of outsourcing by many companies (Verbatim, TDK, Sony, Maxell....) to Moser Baer India to make their optical media. What the quality of these discs are like is anyone's guess. I grabbed some cheap TDK's for the sake of just trailing some music, and they seem reasonable at the moment, but longevity could be awful! There isn't much of a definitive test.

Avoid CD-RW - for longer term storage/ultimate fidelity. These are not burnt in the same way as once-write media. A reaction occurs in the disc which alters the reflectivity (maybe deforming the dye or the metal) and a different system in the read drive is needed to read them. It's harder to read, and arguably harder to write. I wouldn't use them to many times either, as the disc is being deformed each time, and will take the data with less accuracy each time. Great for quick demoing, but not good for ultimate fidelity/quality.
 
A

Anonymous

Guest
This leads us to more esoteric, philosophical questions really: when is a zero really a zero?


Here are a couple of other ways to look at it:
  • Pick up a CD, and stare at the back really hard, and see if you can spot any zeros or ones... (probably not, unless you're superman). Does that mean that the CD does not have the data? obviously not.
  • A little less insane: I burnt a cd the other day and took it for auditioning. Popped it into a $1000 Arcam CD player, and it wouldn't even recognize the CD. Popped it into a $100 sony, and it was fine with it. A few questions arise (all rheotorical):
    • Is the CD a perfect bit wise match? (Actually, not sure. At this point, I'm not even sure how to define a perfect bitwise match)
    • Is Arcam a rubbish CD player? Depends on your definition of good and bad, really.
What's common about both scenarios?

So really, a cds being a perfect data copy really is a function of both the CD as well as the CD player.

A 'Good' CD player, in my opinion, should have enough software/hardware capability to read the CD, do error correction, and then play the result. I'm a software guy, so really have no clue what that would do in terms of cost from a hardware perspective. It's almost like you'll have to have a small computer in there with a bunch of software running on it to do reading, error correction, buffering of data etc before than shunting the bits out. The whole business of clock speeds etc. is beyond my deep understanding.

At that point, you can either buy a really expensive CD player, or just rip the CD lossless. and play it through a DAC.

So here's my synopsis:

It's a bit wise 100% match if you decide you want to rip it. and replay it. Otherwise, it is still a bitwise 100% match conceptually, but realities of the CD player being able to read it will come in the way. (See if you stare at a CD long and hard, it doesn't help if all the information is really there. You can't read the zeros and ones.. Maybe you can lick the CD and see if that helps. :)

The whole JPEG load/save is not a good analogy because the algorithms are not symmetric.
 
A

Anonymous

Guest
Oh, I so wanted to stay out of this but...

There is one and one only measure of the content of the CD, that is the hash sum of the individuals files (tracks), a pattern count of the 0s and 1s which make up the data. A bit perfect copy will have the same hash values per track, which means that the content of the CD is exactly the same as the original. There isn't any wriggle room in this, it isn't about depths of grooves or quality of vinyl. You can comfortably prove this to yourself by playing the original and copy on an oversampling CD drive with optical out and checking the bit patterns match or ripping both the original and copy and comparing the resulting files. The only reason CDs are pressed rather than burnt is speed - even the fastest burner will take several minutes to burn a full CD while a press will produce 100+ in the same time. And the Red Book standard is not that high a quality, it was more about making sure the relatively poor lasers et al of the day have some chance of reading the disk, and as a standard is rather full of flaws (hence why some CD players struggle with some discs).

Ok, so the above is absolutely irrefutable fact. A bit-perfect copy of a CD contains *exactly* the same data as the original and if you copied it again the next copy would also be identical. Making a bit-perfect copy of the whole CD is easy with the right software and hardware, which is not going to include the stuff that came bundled with your consumer PC/Mac, and verifying that it is bit perfect is easy (try jacksum). Making a bit-perfect copy of each track is much easier and the rip and compare method suggested above would demonstrate the veracity of the copied tracks.

This is true of any digital file and is one of the advantages of digital as a store of data; this would include JPEG format images - saving a file is not the same as copying it and data is lost in the saving only if you use poor software or poorly configured software. This is not the same as a photocopy, which is in part analogue, or completely analogue on the older copiers, hence the quality loss. A laser printer making copies of the same file is closer except that the analogue conversion step (the actual sealing of the toner to the paper) is prone to variance e.g. toner particles becoming displaced or temperature variations along the fuser.

However... The physical qualities of the CDs will vary e.g. their weight and weight distribution, and this can cause issues with vibration, and that vibration can have audible effects on the components that convert the digital to analogue and amplify the analogue. So it is possible, particularly with lower quality burnable CDs (different qualities really exist...) that the copy is badly balanced and causing excessive vibration, or differently balanced and causing different vibrations. It is of course, as anyone who has spent time manually ripping their CD collection, entirely possible that the original was badly balanced and the copy is better...
 

MAre007

Well-known member
Dec 3, 2010
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groberton:I am not worrying about one sounding inferior to the other. Logically, there should be no difference. A copy of something as black and white as a 1 and a 0 should be faithful to the original, especially with verification of the copy. Therefore if the CD reads 11110100101010101001010101 1 1001010101010101010101010101 10100101010101010 and the copy reads 11110100101010101001010101 1 1001010101010101010101010101 10100101010101010 and it has been verified as the same then there should be no difference.
I find it funny that the photo/picture analogy came up. If you scan a photo, print it, then scan it again, and print it again you will see a loss in quality each time because each time it is put into the analogue domain (on paper).

If you copied a digital photo file 1000 times and then printed it out - it wouldn't be any different to the original file as the file is still the same - it has always remained in the digital domain. And there lies my logic, a copy of a CD remains in the digital domain, so it should be indistinguishable from the original. I can see this argument running for a while - the interesting part is that those who think there is no loss in quality will invariably have a computer/PC/Mac source in their signature...

I completely agree!
 

aliEnRIK

New member
Aug 27, 2008
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Jitter will make a difference.

Few people seem to realise that whilst cd is 'supposed' to be a 16 bit medium, jitter tends to make it around 12-14 bit dependant on the equipment used (Most people on here will have cd players around the 14 bit mark due to jitter)

Burning a data disc on a computer will be perfect as a storage medium (as long as the disc doesnt break down), as the computer will always negate the jitter. Playing a cd back thats been burned on a computer on a cd player does NOT as it works completely differently - so jitter will come into play. The computer created jitter and burned it to cd, the cd player picks up that jitter and even adds its own.
 
A

Anonymous

Guest
I can see with my bare eyes that the Earth is flat, and there's plenty of theories available on the Internet that confirm this.

Also, I've found that what I write in my word processor, will be slightly detoriated while copying the text into the What Hi-FI? text window. Some words are misspelled, and the grammar is shaky at best.

. . .

In the real world, a digital copy is 100% identical to the original. If it's not 100% identical, it's a failed copy. Something might get wrong when you are burning the data onto a CD, but a copy failure like that will be easily spotted by your computer and will probably make the CD un-playable.
 

Lee H

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Oct 7, 2010
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From EAC website...

"It works with a technology, which reads audio CDs almost perfectly"

So, "almost perfectly". This would suggest that a copy isn't as good as the original
 

Mr Morph

New member
Aug 16, 2010
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Hasn't this conversation happened before? I avoided it last time...

I can tell you this much, if you copy a Minidisc to another Minidisc via an optical link (repeatedly) there is considerable loss. And this is clearly audible! The first generation copy does sound similar to the original, but after that the second generation copy loses the 'cutting edge' of the sound. In fact, it's like listening to the music through two entirely different machines, so there is obviously some loss via the electrical to light conversion. This has always made me wonder about D/A conversion, and how much of the digital is actually picked up from the digital stream.
 
A

Anonymous

Guest
Lee H:
From EAC website...

"It works with a technology, which reads audio CDs almost perfectly"

So, "almost perfectly". This would suggest that a copy isn't as good as the original

Except that is in reference to the imperfections on your purchased CD (and a translation from the more precise German). The original software behind these copiers is cdparanoia, which will keep trying to read every single bit of a CD if it fails the first time (my config has it trying 40 times before it gives up). The non-exact result is not a result of the copying process but the imperfections in the original CD that may have caused bit loss in real-time playing but is corrected with the copying process i.e. the copy could be better than the original...
 

fatboyslimfast

Well-known member
Jan 10, 2008
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Mr Morph:
I can tell you this much, if you copy a Minidisc to another Minidisc via an optical link (repeatedly) there is considerable loss

Don't forget that Minidisc uses ATRAC - a lossy compression format, so copies of copies will degrade without a doubt.

CD copies generally tax the player more than a pressed disc, due to the way the CD player can read the burned disc compared with a pressed version.

A CDR drive may show bit-perfect results from a copy as it isn't reading in realtime, and can re-read any sectors it deems necessary.

An Audio CD player cannot do this, as it is effectively streaming. Any errors have to be interpolated rather than re-read, hence the possibility of lower quality output.
 

Tonya

Well-known member
Sep 9, 2008
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Greetings from -22 centigrade, this really is the weather to huddle around the warm, satisfying glow of an old valve driven amplifier, if only I had one.
Fortunately my Onkyo SR607 generates enough heat for the whole family


Been following this thread with interest (as I do with most of the stuff in here!).
Several posters bring up several valid points and my take on this is based on nothing more than my own experience and technical day to day knowhow.

If a copy of a CD is a perfect bit-for-bit copy will it sound identical?
Well theoretically yes.
On most domestic CD playback transports, the laser and error correction circuits are optimized for silver discs (commercially produced) that have a high reflective property.

A burned CD has a bluey/greeny reflective layer and is not so reflective which means it is not so easy to extract the perfect digital information without adding error correction.

Now in saying that, unless you have extremely "golden ears" and an insanely expensive setup, you probably won't hear any difference providing it was copied at a resonable speed and on a good specification PC that doesn't introduce any unwanted anomalies such as noise or jitter.

Unfortunately, today's kids are brought up on MP3 quality and will probably never get to hear the emotional sound reproduction that a good vinyl pressing of a good recording on a good turntable can provide.
Let's face it, digital music is still an approximation (a mere sample if you will) of what went on in the recording session.

Finally, may I take this opportunity to wish both WHF staff and fellow forum-ites a very musical Christmas and a high definition New Year
 

Mr Morph

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Aug 16, 2010
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Tonya:

Unfortunately, today's kids are brought up on MP3 quality and will probably never get to hear the emotional sound reproduction that a good vinyl pressing of a good recording on a good turntable can provide.

I want to Marry you!
 
A

Anonymous

Guest
Tonya:

Unfortunately, today's kids are brought up on MP3 quality and will probably never get to hear the emotional sound reproduction that a good vinyl pressing of a good recording on a good turntable can provide.
Let's face it, digital music is still an approximation (a mere sample if you will) of what went on in the recording session.

Finally, may I take this opportunity to wish both WHF staff and fellow forum-ites a very musical Christmas and a high definition New Year




I'll join you in wishing everyone a very musical Christmas and a high definition New Year.

But the bit about vinyl is only true in respect of CDs i.e. it is true that there was more information stored in the studio than a CD can reproduce, limited as it is to 16 bit and 44kHz, and that a good pressing (rare) on a good turntable (how much is that? And you have it set up in a filtered air room that is itself built on shock absorbers, yes?) can provide better reproduction. But studios use FLAC for their master recordings while they have never used vinyl as the original medium. So FLAC and DAC provides the potential for at least as good a reproduction as any turntable. But maybe you need a DAC that adds some hiss? <me ducks>
 
A

Anonymous

Guest
I love this Forum. Extremely civilized, and no one's taking pot shots at each other. (It's not a discussion either, everyone's just spouting their own theories, but that's ok). (Seriously, I mean it, I'm not being sarcastic. And I'm not being sarcastic when I say that either). No, really.

Merry xmas!
 

Trefor Patten

Well-known member
Mar 31, 2008
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I have read all these posts with interest as in my experience the vast majority of cds copied via my Mac to a hard drive and played back via Airport express/TCI/Dacmagic sound noticeably SUPERIOR to the original cds. They did so prior to the investment in the Dac which I always put down to the error correction in the computer rips. Now, the Dacmagic is obviously the major factor. True, I did not have a high-end CD player (just an aging Marantz something-or-other SE) but I have never regretted going over to computer audio, Most importantlyI have not heard anything superior in a CD player under £1,000.
 

SteveR750

Well-known member
Mar 11, 2005
560
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18,920
putt1ck:
Oh, I so wanted to stay out of this but...

There is one and one only measure of the content of the CD, that is the hash sum of the individuals files (tracks), a pattern count of the 0s and 1s which make up the data. A bit perfect copy will have the same hash values per track, which means that the content of the CD is exactly the same as the original. There isn't any wriggle room in this, it isn't about depths of grooves or quality of vinyl. You can comfortably prove this to yourself by playing the original and copy on an oversampling CD drive with optical out and checking the bit patterns match or ripping both the original and copy and comparing the resulting files. The only reason CDs are pressed rather than burnt is speed - even the fastest burner will take several minutes to burn a full CD while a press will produce 100+ in the same time. And the Red Book standard is not that high a quality, it was more about making sure the relatively poor lasers et al of the day have some chance of reading the disk, and as a standard is rather full of flaws (hence why some CD players struggle with some discs).

Ok, so the above is absolutely irrefutable fact. A bit-perfect copy of a CD contains *exactly* the same data as the original and if you copied it again the next copy would also be identical. Making a bit-perfect copy of the whole CD is easy with the right software and hardware, which is not going to include the stuff that came bundled with your consumer PC/Mac, and verifying that it is bit perfect is easy (try jacksum). Making a bit-perfect copy of each track is much easier and the rip and compare method suggested above would demonstrate the veracity of the copied tracks.

This is true of any digital file and is one of the advantages of digital as a store of data; this would include JPEG format images - saving a file is not the same as copying it and data is lost in the saving only if you use poor software or poorly configured software. This is not the same as a photocopy, which is in part analogue, or completely analogue on the older copiers, hence the quality loss. A laser printer making copies of the same file is closer except that the analogue conversion step (the actual sealing of the toner to the paper) is prone to variance e.g. toner particles becoming displaced or temperature variations along the fuser.

However... The physical qualities of the CDs will vary e.g. their weight and weight distribution, and this can cause issues with vibration, and that vibration can have audible effects on the components that convert the digital to analogue and amplify the analogue. So it is possible, particularly with lower quality burnable CDs (different qualities really exist...) that the copy is badly balanced and causing excessive vibration, or differently balanced and causing different vibrations. It is of course, as anyone who has spent time manually ripping their CD collection, entirely possible that the original was badly balanced and the copy is better...

Nicely put, and the only post that recognises its *just* digital data same as anything else. I know from experience that making mulitple copies of RAW image files make no difference to quality, only when you start messing around with lossy formats such as jpg.
 

Tonya

Well-known member
Sep 9, 2008
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All valid points, of course on a purely technical level, a CD will contain more "information" than a slice of vinyl, but I was refering to the pure emotional experience of the analogue format.
I use state of the art digital equipment daily but call me old fashioned, I do like the pure analogue waveform that only vinyl provides.
Words like "warmer", "Non-fatiguing" and "relaxing" spring to mind.

But I have this discussion on a regular basis and most agree to disagree!

IMHO, the digital medium brings both advantages and disadvantages to the table.
For example I embrace the improved resolution that digital TV delivers but hate the artifacts that appear in dark backrounds and on some scene fades/fast moving objects.
DVD was a step up from VHS but it still sucked.
Even on BluRay there's compression at work and by it's very nature compression will strip out information and is a compromise.

I still watch the occasional LaserDisc at home and my reference sound is still the Sheffield Labs direct-to-disc pressing of Thelma Houston & Pressure Cooker's "I've got the music in me".

Now back to my roaring open fire (the ultimate analogue comfort) :)

Wishing one and all a very musical Christmas . . . .
 

manicm

Well-known member
May 1, 2008
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putt1ck - all very well but how exactly do you achieve a 'bit-perfect' cd copy?

I've burned EAC/AccurateRip bit-perfect rips onto CD but there are too many variables:

1. I have found burning software to be inconsistent.

2. I have found different brand CD-Rs to give different results.

3. They have never sounded quite as good or the same as the original.

4. There were dedicated CD copiers that did a good job but these don't exist anymore, except for expensive, industrial grade machines.
 

SteveR750

Well-known member
Mar 11, 2005
560
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18,920
manicm:
putt1ck - all very well but how exactly do you achieve a 'bit-perfect' cd copy?

I've burned EAC/AccurateRip bit-perfect rips onto CD but there are too many variables:

1. I have found burning software to be inconsistent.

2. I have found different brand CD-Rs to give different results.

3. They have never sounded quite as good or the same as the original.

4. There were dedicated CD copiers that did a good job but these don't exist anymore, except for expensive, industrial grade machines.


Using a CD player to check the technical validity of the data is flawed perhaps, but of course it is ultimately the only important test.
 

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