A Copied CD sounds no different to the original

Posted by: DynaudioBoy on 15 May 2003

Hi

This is my first post. I am a Computer Science graduate and kinda want to say something about CD copies that may cause a reaction.

BTW I have recieved a NAC72/NAP140 and am enjoying it very much! and now awaiting on a hicap after some advice.

I am going to prove to everyone that a CD copy does sound exactly the same as the Original, and I have'nt even listened to both in a controlled blindfold test.

Sounds like magic, well it is it's the magic of digital.

First you will need to know how a CD works so click Here

Obivously there is only one way to store information on a CD whether it be audio or the computer software you are currently using to read this post, using pits. Now with these pits all you can store is numbers, it how you translate those numbers which determines what information is stored on the CD, like Audio or Software.

Click here to see how to store numbers using binary notation using those pits to represent a 1 (on) and the absent of a pit to represent 0 (off)

DVDs are exactly the same as CDs except have smaller pits which means more numbers and more of the information on it, whether it be audio/video/software hence better sound and picture. Software is a term to describe tools that are stored on CD like the internet browser you are using right now to read this post.

Now here is my point, everything that is stored on a CD is stored in exactly the same way using binary notation as shown by the howstuffworks website. Now when you read a CD using a computer if the CD is not damaged you will read exactly the same information everytime, there is a good reason for this. Computers "crash" go wrong don't do what thier told etc, this suprisingly is because a side effect of using binary. With binary there is no in between on and off, it either is working or it isn't. So if the CD is damaged and one of those bits are set wrong then the software will not work! So when you copy a piece of software (which is illegal due to copyrights), you are copying those 1s and 0s via reading the pits. If one of those pits are incorretly copied say a 1 was now a 0, that software will not function at all due to the side effect of digital.

Recap
When copying CDs you are copying 1s and 0s by reading pits.

Not copying audio/video or software.

It only becomes one of these forms when you interpret the numbers on the CD to actually be read in the required mode if you like, mode being audio/video/software.

So when you copy a software CD you get an exact copy of the original otherwise the software would'nt work.

When you copy a audio CD you get an exact copy of the original because the computer does'nt know what it is copying, it is just reading those pits and reproducing them on the CD copy (CDR).

So how can a copy of an audio CD sound any different at all to the original if it has exactly the same information on it?


Just like in the shops all the CDs in that shop as long as they don't have physical damage will sound exactly the same.

Smile
Posted on: 16 May 2003 by Mr_Sukebe
Here's a few more thoughts to add:

- I do believe that CD copies more certainly ARE very accurate. Lets face it, it would be a pretty rubbish recording medium for data if it suddenly started losing information.

- Jitter. A number of people have mentioned it here. I thought it might be worth re-iterating what it is (as I understand it).
The DAC that you use within your audio chain (whether integrated with your CDP or external) completes the job of converting digital information to an analogue waveform.
It is expecting the data to arrive at teh frequency it was sampled, i.e. 44.1khz, meaning that it should be sent a data point once every 1/44100th of a second. Now what happens when a signal is slightly delayed and arrives slightly late, or even early. This is what results in jitter or timing error, as the DAC will create a slightly different analogue waveform due to the sonic interactions.
As I understand it, jitter is induced by 3 key methods:
1. Data transmission issues, e.g. between a CD transport and an external DAC due to having to pass down additional wires (hence why Naim avoid this)
2. Poor transports
3. Data errors. CDs have error correction built into the data bytes. I believe that 2 bits of information in a data byte is used SOLELY for error correction. Now the result is that whilst the data BYTE may be corrected, the process to achieve this results in a slowing of the data throughput, hence a timing error.

With regard to CDRs, my belief is that the data written really is effectively 100% perfect, however I believe that timing errors are increased during the write process.

Personally I really do think I can hear distinct sonic differences between an original and a copy.
Posted on: 16 May 2003 by bjorne
quote:
Originally posted by Tango:
I could have sworn that sometimes my CD-R's seem to sound better than the originals that they were copied from.


One explaination I read about this is that the recorder burns better defined "holes" and thus makes it easier for the cdplayer to read the bits= better sound....
Posted on: 16 May 2003 by Andrew L. Weekes
quote:
A lot of very high performance analogue electronics is really black magic - no-one really understands it, even if there are models that explain the gross behaviours.


I think this depends upon the definition of 'understand'.

One can usually correlate a change in performance with a change in the electronic behaviour, but it's harder to do predict the other way around. Certain basics have to be right, but thereafter the ears are important.

It's not black magic though, just rigorous method, with sometimes unpredictable outcome!

Date: February 23, 1999 02:33 AM
Author: julian vereker
Subject: light, jitter & other things

A signal appears to travel at about .6c in copper, ie in 10ps : 1.8mm.
This means one has to be rather careful with the design of the pcb in
the area around the input to the DAC (to put it mildly).

The signal only needs to be 'without jitter' at the input to the DAC,
one can tollerate timing errors elsewhere in the player - in fact the
data coming into the fi-fo memory is not very accurate at all but it
is important to keep the noise in the system down to stop it affecting
the signal in the important places .

<snip>

julian


The FIFO should make the player insensitive to jitter on the disk (which is a real and well documented problem - technical computer mags actually evaluate such errors) but in reality, it does seem to have an impact.

I've heard good and bad copies - the disc / recorder interaction is crucial here. Not all recorders perform proper cal to disk, so you can get incompatibilities. There's no universal rules.

Andy.

[This message was edited by Andrew L. Weekes on FRIDAY 16 May 2003 at 15:47.]
Posted on: 16 May 2003 by Tango
quote:
Originally posted by Greg Beatty:
A guess about why CR-Rs can *sometimes* sound better than the original.

The CDR's that can sound better, and, incidentally, the kind a friend who tested several kinds with his CD 3.5 found to sound best, are the ones that have a green surface. TDK used to be this way, don't know if they still are.

The green surface can reduce read errors compared to the original (non-green) CD.

Oh, another reason is if the original CD is badly scratched - say a flea market special (I have several of these). The copy will be clean and can be read with less error correction.

- GregB

Insert Witty Signature Line Here


There may be some truths here. I use mostly green laced CD-R's and some other "coloured" ones too, mostly manufactured in the Far East. Strangely enough, my cd player is also a Naim 3.5. But I must also say I do send most of the recorded CD-R's to my brother overseas who uses non-naim high end equipment, and the feedback I get from him is that he is mightly impressed. He thinks it's to do with my CD Burner, a Sony CDX160E-H1.

Oh, btw, all my originals are authentic original labels, no place for cheap budget ones, and my first CD's from the mid 80's still look as new today.
Posted on: 17 May 2003 by Minky
A seat on the next space shuttle to the bright spark who can explain :

1) Why copy protected disks can't be copied.

2) What witchcraft is in the chip upgrade that allows old Naim CDP's to read them.
Posted on: 17 May 2003 by jpk73
Nero does not do real copies. Clone CD is of the bit for bit type originally mentioned. // Anyone know what free software I can use to determine whether two discs are bit-identical.

CRC32

The CD digital audio format does not have a proper filesystem, and it does not need to. The tracks are written sequentially down the track (yes, a CD has got one track, like a record), you have a TOC at the beginning (containing time-based information) and that's it.

Very important point!!

I could have sworn that sometimes my CD-R's seem to sound better than the originals that they were copied from. // I think its quite possible for there to be jitter on the original cd and that jitter can be reduced by the copying process, hence improving the sound.

Yes, when pressed CD has bad quality, e.g. "starsky": hold the pressed original against a very bright light and you will see uncountable small holes...

The green surface can reduce read errors compared to the original (non-green) CD.

The quality of media is essential for the quality of the copy. I use Mitsumi SG (or Mitsui labelled by other brands such as HP, Boeder etc. - you can check the manufacturer of the blank disks with cdrid).

- Jun
Posted on: 17 May 2003 by Minky
quote:
I believe the usual reason why copy-protection stops burners copying the CD is due to faulty layout (hence why they shouldn't be allowed to call them CD-DA) e.g. putting tracks before the TOC or tracks that say they're 3GB in size etc etc therefore the burner tries to make sense of it and has to re-read it loads of times, or just gives up.


quote:
Nero does not do real copies. Clone CD is of the bit for bit type originally mentioned. // Anyone know what free software I can use to determine whether two discs are bit-identical.


So, if copy-protected CD's fool the copier into thinking something is wrong by altering the format of the disk, "Clone CD" should still be able to copy them ?
Posted on: 19 May 2003 by markjp
I copy CD's using a Marantz twin deck. The quality of the CD sounds the same as the original but the copied CD is quieter. I always have to turn the volume up on my CD3.5 to compensate. Can anyone explain the reason for this?

Mark
Posted on: 19 May 2003 by syd
quote:
Originally posted by markjp:
I copy CD's using a Marantz twin deck. The quality of the CD sounds the same as the original but the copied CD is quieter. I always have to turn the volume up on my CD3.5 to compensate. Can anyone explain the reason for this?

Mark


I presume Marantz have set the default Digital copy level a few decibel lower but I can't think why. When I copy digitally from my micromega to to the Pioneer the level appears to be the same, although you can raise or lower the digital level on the copier. Perhaps your Marantz has this facility and it's not set correctly. Check your manual.

Yours in Music

Syd
Posted on: 21 May 2003 by Andrew L. Weekes
Donate my ticket to charity Wink

quote:
A seat on the next space shuttle to the bright spark who can explain :

1) Why copy protected disks can't be copied.

2) What witchcraft is in the chip upgrade that allows old Naim CDP's to read them.


1) I can't do that, but I can tell you how to copy them!

http://forums.naim-audio.com/eve/forums?a=tpc&s=67019385&f=38019385&m=5061937006&r=8321997106#8321997106

2) I seem to remember Doug or Richard mentioning the corruption was in the subcode data - I guess the new firmware deals with this more elegantly.

quote:
So jitter can definitely be present and be altered during digital transfer


It can definitely be present, but not really altered in the sense I think you mean. Jitter can only be present when the data is being clocked in our out of something. When it sits on the HD, or the CD it has no inherent jitter.

The CD disc CAN have inherent jitter in the data pits, and this is measurable on CDR's (look at PC Magazine for review examples).

The sensitivity of subsequent stages to the jitter that's then introduced when the disc is read, is a seperate matter.

This is Linn's argument behind the CD12 - how do you tell when a pit on a CD starts or stops it's a bathtub with sloping ends.

Linn run some proprietry software, on some very fast silicon, to negate the effect of any jitter inherent to the decisison levels made upon the RF eye waveform, as far as my understanding of the situation.

Andy.