orginal or copy

i tested one original audio cd side by side of it's copy in blind listenning and i and my friend detected their difference.
can you believe me?!
it's question to me for once we prefered copy sound to orginal in track 1 and once in other track(8) we prefered orginal cd sound!!!
track 1 of orginal cd had played so much in my system before but i did not played track 8 of orginal cd before our test, and copy cd was played just at our test time.
can you tell me i'm wrong or this is possible?

 

A copied CD will not be identicle to the original.
The copy is never perfect, jitter gets introduced and 100% of the data on a cd is never picked up by the CD player. Different areas of the copied CD will be easier/harder to read than on the original therefore different sound.

Simple when you realise how crappy CD's are

 

It seems odd that a copy can sound better, as the process inevitably causes a loss of information compared to the original. And decreased resolution results in a sharper sound.
With a good quality Audio only blank CD and a good reecorder the difference can be hard to tell, but copying surely doesn't add any kind of quality correction to the original.

Also note that a difference may seem an improvement at one and a worsening at a later stage.

 

In my experience on reasonably good kit a copy is always markedly inferior to the original. The copy gets worse the higher the copy speed was.

Bob

 

A digital copy of a CD is bit-for-bit identical to the original, so any differences you're hearing are entirely down to CD-R versus standard CD issues if the copy is digital rather than analogue. Jitter is irrelevent to this question, as is data loss, although both these may, of course, be of relevance to analogue copying.

-- Ian

 

A lot of daft inferences there. Why shouldn't a copy sound better?

Show me the evidence that 'a copy has more jitter than the original' - here is a counterargument:

The original is a mass produced pressing and is therefore made to a dimensional tolerance = jitter. The copy is burned by the timing of a x-tal oscillator. Which is more stable??

Anyway, which DOES sound better, more or less jitter? Lets have some reasoned argument. At the moment this is just chinese whispers...FWIW I have often preferred the sound of copied CDs in a very subtle way.

 

There certainly is no "loss of information" when you copy a CD. The copy will be identical - regardless of the copying speed. If it weren't the case when you copied data CDs for computers they'd get corrupted....and the obviously don't. What comes out is 100% bit for bit identical to the original.

Michael.

 

Hi.

If a good cd recorder is used for the copy (eg not a PC they often don't have error correction on audio formats) then errors that can be corrected by the reading transport will not appear on the copy, if there are scratches and marks on the original, then there is the possibility that the copy will read with less errors.

Chris

 

Eh? What gives you that idea?

From the POV of a computer, what's on a CD is data. The content of that data is irrelevant, whether it's audio, video, or anything else. A CD->CD copy on a PC either works correctly (is a bit-perfect copy) or it doesn't, in which case your burning software will flag errors. If your burning software doesn't flag errors, throw it away and buy some that does.

Domestic audio CD burners are an excuse for manufacturers to sell "audio" CD-Rs, which are the same as any other CD-R, but have a tax imposed on them to make them far more expensive to buy. They're useful for making analogue recordings onto CD, but pointless for CD->CD copying if you already have a PC.

-- Ian

 

a bit for bit copy will (should) sound the same. however when played back there may be differences due to the differences between pressed and 'burnt' media and that interacting with the cd player and it's software.
as for copies sounding better my theory would be somehow dither is being introduced. this can allow detail not usually heard to be realised. don;t ask me how - google it if you don;t believe me. the mechanism for adding dither when copying is not something i'll speculate on though.
cheers


julian

 

Agreed. That would be the only explanation for a difference in sound between a digitally copied CD-R and the original commercially produced CD.

-- Ian

 

I used to think this too, until about 2 weeks ago.

A colleague sent me a copy of Linux he burnt at the highest speed he could and the installation failed, I thought due to either a bug or corruption. The same colleague then copied at a lower speed and this installed fine. I've always thought that copying software would be 100% reliable whatever the speed. Evidently, not so. I'd like to know why the corruption wasn't picked up by the burning software.

 

Did he verify the original copy? Most burning software has an option to verify after burning, I always turn it off because it takes too long, but it's the best way to ensure the copy really worked. The other possibility, of course, is damage to the CD-R after it was copied. One thing I've noticed is that CD-Rs seem very easy to scratch compared to commercial CDs. Either of these are more likely than any other option, if digital copying was routinely error-prone I think the world would have noticed by now!

-- Ian

 

Just shows a lot of people know jack about computers/CD technology and the make up of digital data.

As for the speed/corruption bit, I have never believed that burning media any higher than 12x to be more than a marketing gimmick to make your unit look better than the competition. I never burn audio faster than 4x and usually data at 8x.

Remember these CDRW units only cost £20 now and optics count for a lot when it comes to precision laser burning. Try painting dots on a spinning plate. I guess at 52x speed even a precision crystal has problems, then there is the burn time reaction between the blank media and the laser, excentricities of the disc...loads of factors come into play at very high speeds. In theory it should be pretty much identical but no doubt changes are there, error correction from the original CD transport, the precise pits/burns made by the laser rather than the pressed pits on the original...the mind boggles.

Have to say whatever you/I think it is, I have never been able to tell the difference between a copy and the original CD copy. Then again I do take steps when I copy stuff to make sure all is successful. I still remember the days when CDRW systems were mainly coaster makers.

 

I don't think so Ian. Otherwise he'd surely have picked up errors. However, the point is that at least at higher speeds (perhaps with dodgy CDRs?) it's possible to get imperfect copies. I haven't in the past verified the copies, but now I won't assume they're perfect.

 

Audio CD's are NOT "data" CDRom's

Audio CD's and CDRoms are not the same thing, even though they are on the same plastic disc.

Data CD's (CDRoms) carry additional data protection bits resulting in less capacity per sector.

But wait I hear you say, that dosn't matter as our Audio is protected by CIRC redundancy code...

Well, it used to be until insiduous audio cd copy proectection schemes came along which use the stamping process of CD's to "write" data and CRC's to the audio discs which have been deliberately created to appear as errors when readback. The reason for weakening the protection was because in a CD player, when the CIRC fails, there's an interpolation stage to cover the error. However, that interpolation process is not necessarily happening on the DATA path in a cdrom. So, the crux of these copy protection schemes is that copying the audio fails on CDR drives which don't have interpolation on the data path. The failure is either the drive/software giving up and accepting the corrupt data, or the drive repeatedly failing to read the sector no matter how many attempts it tries.

The moral of this story is that you need to be quite careful in your choice of CDRom drive with which you will rip your Audio cd's. You want a drive which will "do" interpolation for you OR provide the "C2 error status bytes" so that you can correct in software.

 

Thank oedipus you a better discription than i could have done.

 

Oedipus is talking about copy protected audio CDs, which are a different kettle of fish, and a distinct minority of commercially-available CDs (and only recent ones at that).

-- Ian

 

I think bit is bit but it's phisycal shape on media differ from orginal to copy and after playing one track for so many times this shape change and i think copy cd's are better in long term using but for first time listenning orginal is better. some cdroms'laser beam defect shape of pit and land on cd's.

 

I think I remember some discussion way back in the early days of CD recorders to the effect that copies could sound better than the originals; the "explanation" had something to do with CD-Rs having some sort of pre-cut track and hence a reduction in jitter. My recollection is a bit hazy, the technology wasn't very interesting to me at the time and I was a bit dubious about it - it was at a time when there was a lot of Linn-mysticism about. If I recall correctly, Keith Howard may have been the author of some (or all) of the articles.

A recent personal experience with a poorly-made CD-R is interesting. At about the 30-minute mark (of 45) it began skipping - basically it's unplayable in my audio CD player. So, with the above vague recollection in mind, I made a copy on the PC. Put the copy in the audio player - plays fine. Something going on in the tolerances perhaps?