Bit perfect copies

I'm using the Phillips dual tray 2X recordable/rewritable
unit. Does a great job of making bit perfect copies, but
fails miserably as a CD playback unit. This is no big deal as I didn't buy it for that purpose. I think there are several units on the market that can make (essentially) perfect dubs.

Virtually by definition, all CD recorders make bit perfect copies. Can you imagine a manufacturer trying to sell a CD recorder that does not make bit perfect copies? I use the Pioneer 739 (now 839), and it makes excellent copies. Good Hunting. Craig

I used to think that digital meant perfect copies too, but after playing a few data CD-Rs made from audio CDs on a PC, I would occasionally hear a small click . "Rewinding" and playing the passage again usually reproduced the click in the same spot. Playing the same passage from the original CD didn't produce the click. Using a file comparison program on my PC, I found that the CD-R copy was NOT exactly the same as the original audio CD.

Since I used very cheap CD-R blanks that were meant for computer data (free after rebate - from an office supply store), I speculate that the shortcomings with my copies were caused by the disks themselves and a few of the burned bits not "sticking."

My suggestion is to pay as much attention to the media as to the recorder, as even perfect copies may quickly deteriorate if poor media are encountered. This may not be as much of problem with the audio blanks.

The freeware I used was called Test Path, if you wanted to check with your PC how any old copies are holding up.

Previous poster - chances are that your computer had a program running in the background that taxed the pc's memory. Try burning discs with all other applications shut down and there should be no pops or clicks. Data CD-Rs just don't pay royalties to the RIAA but their quality varies as much as CD-Rs for "audio" use.

I use to burn cd-r's directly from the source and I heard clicks and other occasional distortions. I now extract the music from the source and save it onto the computer. I then burn it a 1X (the original speed) and they sound excellent. Also some brands of cd-r's cause problems with auto and high end cd players. I find Sony CD-R's to be the best and most reliable for audio. Memorex is not very good, TDK are blue in color and some audio cd players won't recognize them.

I too have had problems with cheap CDR's. The blue ones that I bought in bulk would skip terribly especially on my car and portable machines. I switched to SONY (silver in slim cases) and have had much better luck ( still only around $.75 each)

There are several audio CD-R units on the market that sell for about $350. There was an ad in the Sunday paper from either Good Guys or Circuit City for a Phillips unit, and Sony has recently brought out the RCD-W1. (The RCD-W1 also has a special offer thru July 31st for a free 20-pack of audio CD-R disks.) I recently bought the RCD-W1 so I can transfer a lot of my vinyl collection onto CD, but have not had the chance to play with it yet. As others have commented above, all of the units do a perfectly adequate job of copying -- but don't expect them to be great playback decks.

Scott, it would be great if you would report on the RCD-W1 when you've had a chance to record some vinyl with it. This unit tempts me, but I've wondered if I'd have to spend money for a pro machine to do justice to LPs. From the promo blurbs, it doesn't sound like the RCD-W1 uses the same A to D technology as their new, pro unit, but who can tell from that stuff? -- Jayson

Some of the answers above aren't exactly true. Most CD-r burners don't make perfect bit for bit copies and can introduce errors as multiple generations are produced. This is in part due to the large amount of data involved with digital audio. The only way I've seen to make true bit for bit exact audio copies of CD's is to use a PC (or MAc) with software that does DAE (digital audio extraction) from the CD and then reburns that data onto the CD-r. Exact Audio Copy is company that makes the only software that I'm familar with that checks the extracted audio bit for bit with the original to make sure the copy is exact.

Thanks for the information chanifin. Would you have the web address of Eaxact Audio Copy?
FC

Check out www.etree.org for links to EAC and other software.

No such thing as bit perfect. To make my point Stereophile had an article about BMG's quality. As you may recall, BMG remarkets CDs to clubs. Stereophile did a comparision between the original CDs from RCA, Mercury and other companys and the BMG pressings. Result was the BMG CDs were digital perfect but didn't sound as good.

To cut this long story short. The bits layed down were identical as will be those you make at home in general. The problem is the timing. The jitter and phase of the bits as they clock into the D/A add distortion to the sound. CD burners are not as good as BMG's so you will be degraded even more.

How do you overcome this? You don't.

I don't think I follow what you're saying - clocking the bits (samples) into the D/A comes well after the reading of the disc, so how does the source (CD vs. CDR) affect the quality at the point of putting it into the DAC? Are you suggesting that a CDR gets read "wrong" despite being bit-perfect where the CD gets read "right"? I also don't understand the concept of "bit phase". Would all these issues go away if the whole CDR was read into RAM before playback began?

I'm very open to the concept that CDRs are somehow inferior to the original CD, though it hasn't been my experience and runs counter to my technical understanding (which undoubtedly could be enhanced). I don't think Stereophile saying CDRs "didn't sound as good" really establishes much as there is an inherent bias there - if it really is possible to make 50 cent copies of CDs that are indistinguishable from the original (using a cheap computer no less), that's not good for Stereophile's business. I'm not saying their viewpoint can't be right, just that it doesn't mean much coming from them.

To answer the original poster's question, I'd use a computer and some easily obtainable freeware or shareware to make the copies. Cheap, easy and effective. -Kirk

Kthomas I agree with you about cheap and effective. But not perfect. There is jitter introduced at all stages of the digital to analoge process. For the digital to digital I was not referring to the error encoding of the original being changed. I'm actually talking about clock in the CDR that governs the placement of the copied bit on the cdr media. When it is not dead on perfect (parts per billion or less) The the decoded signal on playback has phase errors in the analog signal. Ideally even if you had an imperfect clock that would repeat its errors reliably and it was used to burn the CDR and play it back you would have no error in phase in the analog output. But you don't.

Also one other issue. No player reads every bit perfectly from the original play. That's why we have error encoding built in to the process. So you have to read every bit perfectly (typically 700K of them) and then place them back on the CDR without a signal one out of place. If the CDR has a flaw in its manufacture or the laser varies in intensity or location.//error.

I enquired with Linn about problems I had been having while playing CDR's on my Genki. Certain CDR's (roughly 25% of my 'burned' CD's) suffered from occasional background shuffling sounds as well as occasional but very prononced ticks and crackles. Sometimes the CD would hick-up (stop playing mometarily) - at which point the recording would resume playing smoothly again. In the worst cases certain tracks wouldn't play at all. These problems never occured with CD originals - except in one instance when a 'real' CD suffered from the same shuffling background noise. This problem was immediately rectified after I blew into the CD player drawer - presumably dislodging a piece of dust from the laser lens.

My question to Linn:

Hello, I own a LINN system (Wakonda/Kudos, Keilidh, LK140, Genki) - my question is regarding the Genki. It has difficulty reading certain CD's ('burned' copies)- that my old sony can read without trouble. At times I must try skipping ahead in order for the cd to play at all. I tried cleaning the laser - it seemed to help a little. *Most* cd's play without incident. I would appreciate any advice regarding this condition.
Sincere thanks, - Me -.

Linn's response was as follows:

"The Genki CD player may or may not play CDR's and CDRW's because of the following reasons:

1. Many 'domestic' CDR machines have copyright protection coding (SCMS) onthe digital input , so when you copy commmercial CDs the only way to do it is using the Analogue output of the CD player to the Analogue input of the CDR recorder. This will result in degradation because of passing the signal through the D-A and A-D converters in the two machines.

2. There are several stand-alone CDR recorders which will accept digital inputs, but which also accept 48kz digital sources as well as 44.1kz. They do this by interposing a 'Sample Rate Converter' in the signal path, and while this is a good way of getting 48kz audio on to CD ( which have to be 44.1kz ) normally these machines leave the Sample Rate Converter in-circuit while accepting 44.1kz digital audio. This means that the copy will not be a bit-for-bit 'clone' as one might expect and as a result there may be some degradation in quality.

3. If the copy is made using a CD-copying package on a PC, many of these are very poorly implemented, which again means that the copy will not be a bit-for-bit clone, the most frequent problem being that the 'dither' information in the LSB is lost or corrupted. This leads to a loss of
detail and ambience.

4. If none of the above is the case, it may simply be that the physical qualities of the disc ( transmissiveness / refraction of the Polycarbonate of the disc itself, concentricity of the disc, reflectiveness of the metallised layer) are inferior to those of the original pressing. This can sometimes affect sound quality, if only because the CD player will be working harder to decode it.

Please feel free to contact me at Linn Customer Services if I can offer any further advice or assistance."

Best regards,
Richard Johnson

Richard - that's an interesting response. Thanks for sharing it with us. While the audio CDR components appear on the surface to be a really convenient way to make copies, I find it's at least as easy and considerably more flexible to make copies on my PC and that's what I would recommend to anyone wanting to make copies. I have never had a single problem with playback of a CDR that I've made this way. Occassionally, I have a problem in the copying process, but that's immediately flagged and I start over. Once made, though, playback has always been flawless - none of the noises you describe. I play them back in either a Sony ES changer or a Sony DVD-S7700 DVD player, digital outputs in both cases.

One of the advantages to this approach too is that you can verify a bit-perfect copy. Once you've done that, the first three of Linn's responses are off the table and you'd be left with the fourth as a possible answer if you continue to have the problem(s).

I use a fairly recent Dell setup for copying and Memorex CDR blanks. -Kirk

Please make sure you know the real source for the manufacturing of your CDR media. Visit www.cdmediaworld.com for the rest of the story.

Anyway, the only problems I have encountered with cdr's, I have burned over 3,000 disks or "live" recordings, has been when I have used cheap media sourced from poor QA plants.

However, I have received some with skips and ticking from others. When I followed up and inquired about what they were using to record it on it has always turned up as a computer. I use a stand alone unit, Marantz CDR630.

As for Linn's response to the reason some CDP's do not read the CDR correctly, the first 3 reasons are possible implications for not having clones but would have no effect on the CDP's ability to play back. Yes, you would lose some air and slam, at least IMO.

The reason some CDP's will not read CDR's is that their lasers are not able to cope with the difference in refeltivity of the CDR disk. It is that simple. And, of course, as you discovered, if the laser is dirty it will greatly effect the machines ability to read.

Again, I can not stress this point too many times. Do not drink from the well. The CDR may say Maxell, Sony, HP, or what ever, but few of these labels actually make CDR's. They source them out to plants that do and then print their name on them.

Memorex is known to use the cheap plants "Ritek" and have been tested by independent labs to have poor archival abilities. Many others use the same plant. The best information I can give is to tell you to study the media and choose wisely. Visit the site I posted up top. It will be of great help to you.