I recently began copying most of my collection onto CDRs using a recently purchased computer - in other words, recent hardware and recent software. I hear no difference and believe that the reason I hear no difference is because it's extremely easy to prove (repeatedly) that the CDRs are a bit-for-bit exact match to the original CD. If you're hearing a difference, I can think of no logical reason other than that the bits are different, which certainly has been the case with older hardware and software, but has no reason to be the case now. Degradation may also be a real phenomenon, but in that case it is again due to bits that are unreadable and therefore end up at the DAC differently. |
With up-to-date software and hardware, it is easy to prove to yourself that bit-perfect copies are being made when using a computer CDR setup - there are many programs to grab "files" of data off an audio CD and compare them to files grabbed off other audio CDs. Occassionally the copying software reports an error and won't finish the job, but every copy I've ever compared to the original matches perfectly. I sold my Phillips CD copier/recorder, so I can't do the comparison on copies it made for bit-perfect correctness. To the extent that they are bit-perfect and any difference is in jitter induced by the reflective properties of the media, I can't wait for networked components so the perfect copies can be delivered anywhere for playback. It is also annoying to think that a multi-thousand $$ transport can't retrieve data off a CDR as well as a $69 CD drive for a computer. |
I'd like to better understand what is going on in the making of a CDR, because apparently I don't - I thought that the most basic form of creation for a CDR on a computer was a straight reading of the bits off the original and writing of those same bits onto the CDR. What actually happens? And, BTW for the poster who asked - I'm in the process of copying all my CDs - largely to put the copy into a CD changer, freeing the original to be taken in the car, to work, or somewhere else in the house. Putting the CDRs in the changer allows for inserting all the title / track info which gives total flexibility in moving the discs around without having to use the cryptic UI on the player. |
Madisonears - do you have an instance where you still own the original and the copy that sounds different (worse), and assuming you do, can you extract the song files from both and compare? I'd be very curious to know if they compare identically. |
Madisonears - I'll find the exact steps and software I use at home and then post them here. The software is all free, at least in trial version, and by doing so we can be sure we're comparing apples to apples. A general process I've been through several times is extracting song files to the hard drive, which can then be mixed and matched and written back to CDR's. I can extract the same file, say, 10 times using the same software and different software, and then run a compare program against any two of the resulting extracted files. The compare program doesn't know the source of the files, it just dutifully does a bit-wise comparison of the contents. I have never had any problem with getting all N copies to compare identically. Now, I admit to extrapolating from my experiments to my day-to-day copying - I don't compare the files each time I make a copy. In any case, since I typically copy whole CD's to put in a "jukebox" and since nobody but Sony utilizes the CD Text capability of CDs, I do a song-by-song extraction / copy so that I can insert title and song info. Alternatively, you can just make a straight copy of the CD in a single pass - I have never attempted to extract the whole CD image to the hard drive multiple times using different software and comparing the image, but I have little doubt that it would work as well. Another experiment worth trying (so maybe I will :-) ) would be to do the same thing using a CDR itself as the original - there has been speculation that there is something about the physical nature of a CDR vs. a CD that makes it more prone to sounding different. I can't formulate a hypothesis on why that would be, but I'd want to try it for myself first. -Kirk |
Ok - it was a long weekend involving travel, etc., so it took me until last night to perform the tests I had earlier indicated I would undertake. First, just for the record, although I'm 6'2", that's my only possible advantage in any physical confrontation - I'm a wuss and would probably just stand there and get pummelled. Anyway, for these tests I used the following software - Audiograbber v1.62, RealJukeBox2 Plus v1.0.2.178 (Beta), and the slimmed down version of Adaptec's CD Creator software that came with my Dell computer. I wanted to verify that I could retrieve (ie, rip) and write identical files. I used three songs off of Hall and Oates Master Hits. First off, I read them to HD twice each using Audiograbber. I compared their 64-bit checksum using Audiograbber and each of the parallel files matched it's partners exactly. Audiograbber also has an option to compare two music files, and each of the parallel files matched exactly. Finally, using Windows Properties, each of the parallel files reported exactly the same number of bytes. Then I used RealJukeBox and read the same three files to disk and compared them in the same ways to the files I read using Audiograbber. Again, the checksums matched identically, the comparison of each to it's parallel matched identically. Interestingly, the Windows Properties showed that the RJB files were a few Kb larger than the Audiograbber files - on the order of 5K out of 50Mb. Then I did the same test using Adaptec's program. This time the checksums wouldn't calculate - according to the Audiograbber software, if a song file doesn't end in silence, a proper checksum can't be calculated and is indicated by an 'X' at the beginning of the checksum. This is what occurred with the Adapted files. The files also did not compare correctly to the original Audiograbber files. Looking at Windows Properties, the Adaptec files were all either 12 or 14 bytes larger than the Audiograbber files, and looking at the dump of "mismatched bytes" in the compare program it appeared that there were two extra bytes early in the Adaptec files, after which everything lined up perfectly. I don't know what the format of .WAV files is, and I don't know what the Audiograbber program is doing precisely when it calculates Checksums and does compares. The fact that I can repeatedly use an extraction program on a CD song "file" and get exactly the same file, even though they differ slightly from a parallel exercise with a different extraction program leads me to believe that there is a variable-length field in a header someplace that each program utilizes slightly differently, and/or a way of handling the last block of data and the end-of-file marker that would explain the slight differences encountered. Just to prove to myself that you'd get much different (and undoubtedly worse) results using the sound cards conversion, I "ripped" the same three songs using the "analog" setting in Audiograbber's config. Sure enough, the files were all different from the original digital copies, and multiple "rips" produced different files for the same songs. So, then I took my original three songs read with Audiograbber and burned them to a CDR. I then took the CDR and read each of the song files to disk using each of the three programs. I compared each of the files created by reading the CDR to the same file created from the original CD for each program. Audiograbber and RJB compared identically in all three cases. Adaptec did not. Again, I think they're doing something with a header someplace that doesn't have anything to do with the music data, but I have no proof of that. However, it is clearly possible to read/write/read/write ad infinitum with the right computer hardware / software combination and get "perfect" copies of CD and CDR data. Note that I'm not extrapolating that a CDR done in this way will absolutely sound the same as the original CD played back on a stereo system. There may be some physical properties of CDRs that are different than CDs that result in typical CD player/transports to be less reliable in reading them. I find that hard to believe, but nothing I have done here refutes it in any way. What I am definitely saying, though, is that it's easy to retrieve every data bit on a CD or CDR with extremely inexpensive hardware. I also know from professional experience that delivering data from point A to point B "perfectly" is a solved problem, so if getting the data bits to the D/A of choice in our current form is problematic, as it has been widely documented, then we should be pressing for a better interconnect technology, because it doesn't have to be that way. |
Madisonears: I'd still be interested in your comparison of the CDR that you feel sounds different to the original CD. The steps would be thus: Go to http://www.sonicspot.com/audio.html and download the free copy of Audiograbber. Install it. Use it to Extract a song to disk from the CD and the CDR that you feel sounds different. After each extraction Audiograbber reports a Checksum. Take note of each checksum. Alternatively, from the main menu, you can calculate a checksum on any file, so if you miss it the first time around you can make up for it. Then, when you have the two files, go to Audiograbber's main menu and select "compare two file". Select the two parallel files and press start. If they're the same, you'll get "No differences detected" in the status box. If they're not the same, you'll get a bunch of information, none of which you'll want to read. It's hard to tell how much they differ if they differ at all, but my experience with audiograbber is that you should get repeatable results from the same file, so if there are any differences that's probably all we need to know. -Kirk |
Carl - I realize that your comments were not directed to me - I was just attempting to be funny. Mfgrep - I would encourage you to get the CDR burner and do the comparison tests for yourself. I'm curious if you doubt the ability to make "exact" copies from a pure physical standpoint - in trying to divide and conquer the problem, the first thing to do would be to determine if we're comparing apples to apples which, in my mind, is proving that the CD and CDR have "exactly" the same information. That's all I was trying to prove to myself with my tests - how they sound and if they sound different is another test. It shouldn't be surprising that this is quite possible even with a cheap CD transport - there is enough error correction / retry logic built in to insure proper reads, and the writes either work and you get a good copy or fail and notify you. In other words, it's cheap technology with a bunch of redundancy built in. Similarly, setting up a 100Mb LAN in your own home is a cheap proposition these days, again because it's cheap technology with a bunch of built in redundancy. I think the reason transports / interconnects in the audio world sound different is because they're not built with the same redundancy model - there, it is more "send and pray" that it gets there. If it doesn't, you miss it to the audible detriment of the listener. Now, if I can build a 100Mb "transport" for a digital datastream that covers my whole house for less than $1000 and deliver "bit perfect" data anywhere therein at data rates far exceeding redbook CDs (or even SACD's for that matter), then it would seem obvious to me that the future of digital interconnects is NOT what we currently have if it is so prone to error. In any case, I just wanted to clarify that I was only documenting a repeatable test for "perfect" data copies and not making any claim that the test covered the audibility of the copy vs. the original. |
Mfgrep - I can't stay away from the music section at Best Buy either - I find that I buy 7-8 CDs at a time because that's how many I can hold in one hand. In any case, just to plant a thought - if you prove to yourself that the digital copy is identical to the original and still sounds different to you on playback due to jitter, laser difficulties or whatever, you have to ask yourself why that is, since the same cheap plastic CD player in your computer can read that CDR and make as many more perfect copies as you care to make - ie, no generational loss. If it can do it (and it can), why can't CD players / transports? At some point inside a CD player / transport, you just have digital information, regardless of where it came from. If we can demonstrate that a cheap CD drive in a computer can reliably read that digital information and present it wherever it needs to go, then we, as consumers, should demand that makers of CD players / transports provide the same performance, and it shouldn't cost many thousands of dollars. |
I'm not sure anyone else feels like any fuss is being made - this seems to be a conversation amongst several people interested in understanding what the results and effects of CD copying are and, more importantly, what the critical aspects of the process are for getting "acceptable" performance. I don't think anyone has tried to convince anyone else of what they're hearing for quite a while in this thread. I'm certainly not trying to convince anyone here that they're not hearing what they claim. In fact, I absolutely believe everyone who says they hear degradation. I'm interested in hearing about the types of degradation they're hearing so I can go back and listen more specifically for myself. What I'm really interested in is in trying to understand why they're hearing degradation. It's possible that it's fixable immediately, and it's also possible that, while it may not be immediately fixable, we'll collectively understand what it is we're waiting for that will fix the problem. In the meantime, it seems that one thing that is indisputable is that it is possible to make bit-perfect copies of CDs to CDRs, and yet you keep saying they're not. I'm having trouble understanding what you're basing that on - If I can read and write 650MBytes of data and calculate a checksum across them all and do this over and over and over and repeatedly get the same checksum which has, literally, one in many billions of a chance of matching without the data being exactly the same, and since I do it over and over and over and get the same answer, and the odds of that are therefore billions to the N power - at what point does it become illogical to argue that they're not "truly perfect"? They're not truly perfect from CD to CDR because the way the bits are physically stored is different, but from an information standpoint they're identical. To state that there are no "perfect" copies in the face of these odds doesn't seem to do anything but attempt to cloud the discussion indefinitely, and it would be much more interesting to discuss what is making the CDR copies sound different to those who are experiencing the degraded sound. -Kirk |
Mfgrep - all my experience is with computer CDRs. I used to have one of the Phillips dual-tray copier machines which required the audio media, but I don't still have it to run any kind of comparison test with. There is physically no difference between the two media, just a bit that is set saying this is an audio CD and therefore can be used in an audio CD recorder. Computer CDR drives don't pay any attention to that bit, and computer CDR media doesn't set it. Robba - absolutely understood. There are three "chunks" - reading the media, getting the data to the DAC and then what the DAC does with the data. All my comments have related only to the first chunk. You're correct that jitter is introduced in a different chunk - namely, the second one. Jitter is of the nature you describe - both the sending and the receiving device have to "clock" the data, and if they are out of sync, you can get "lost" or bad data. Since there is no retry logic, the DACs two choices are to play the bad data or throw it away, either of which would cause audible degradation if it happened very often. One solution seen on some high end transport / DAC combos is cabling that forces the two clocks to act as one, thereby eliminating lack of synchronization. This is a better solution if you're limited to "send and pray" transmissions, but there are much better methods by implementing redundancy into the system. There has to be retry capability, or multiple copies of the data sent so that it has to fail on all connections before the data can't be processed. There are a number of strategies that can be employed with a small re-engineering of the interface, and that have been deployed in other communications-related applications. In any case, the main point of parts of this thread is that the first chunk (reading the data) is a "solved" problem, at least when using computer CD drives, and that if a CDR sounds different than the original CD it's either because 1) the copy wasn't "perfect", or 2)some as yet unexplained aspect of current CD transport /player intereactions with CDR media that differs from CD media. |
Okay, I'll quit saying that I fully believe / agree with everyone stating that they hear differences. I'm also more than happy to grant anyone who has the opinion that CDRs sound worse and that's just a fact of life the right to do so. As any of this pertains to audio, I'm just an enthusiast and like to discuss the various topics. In my professional life, I run a software development department responsible for the collection, processing and delivery of financial information from and to around the globe. Centrally, we handle transaction rates into the tens of thousands per second, and experience data rates in the tens of megabits per second of data. If we miss a single trade on Intel, we hear about it from the clients. If we were to screw up a price and deliver it to clients, we're in deep doo doo. All of this done in an environment that is loaded with every acronym audiophiles have come to fear. What's more, when something does go wrong, we can find exactly where and what went wrong and preclude it from happening again. The same concepts apply to getting a price from the East Timor silk futures market and delivering it Scandanavia as do to reading a CD or CDR and delivering it to a DAC even though the engineered solution is different. For anyone who's curious about the handling of digital music and is wondering how best to spend their money over the next few years, these are important concepts to understand. I'm totally convinced that in some short number of years, the notion of current transport technology will be obsolete, replaced and bettered by something costing a small fraction of a current high-end transport. In the meantime, that solution doesn't exist today, and being an audio enthusiast I want the best I can have today while understanding that money spent today is money that I could spend tomorrow. |
Craig - Your experience mirrors that reported by Stereophile (JA?) when they reviewed one of the Phillips audio CDR recorder/players - he, too, noted possible, slight degradation, but overall was very impressed with the copies that were made. It's not surprising that the W739 makes excellent copies but sounds like a "cheap" CD player on playback - it should be a lot easier (ie. cheaper) to make accurate digital copies than to do quality D/A conversion. |
To the extent that we're talking about the accuracy of the copy being the dominant variable, it doesn't make sense to me either. You can prove the accuracy of the copies made by a computer CDR drive and I'm guessing (since I haven't done it myself) that you can prove it's not a "perfect" copy when you use an audio CD recorder. That's saying that it sounds better off a CDR when the bits are changed a little as opposed to not at all. The notion that using an "audio" CDR disc vs. a computer CDR disc and get better sound is difficult to explain - the only difference in the audio CDR is the interpretation of the bits and the royalty that gets paid on them. But, it would be easy to eliminate this variable - just use an audio CDR to make a copy in a computer CDR drive and compare it to an audio CDR made in an audio CD recorder. |
Tubegroover - I'm quite certain that many people have experienced making "copies" that were so different that the differences could be heard by anyone - it's easy to do even with very recent software and hardware. Just configure your "ripping" software to operate in analog mode and the path will be from CD through a D/A conversion, followed by an A/D conversion to be written to the CDR. There is nobody on this thread, I'd be willing to bet, who wouldn't be able to hear the differences imparted by such a low-quality set of conversions. Couple this with the widespread reports of earlier software / hardware producing degraded "copies" and I think there are a LOT of CDR "copies" in the world that sound between worse and unlistenable compared to the original. If we could eliminate these variables / experiences, I think the division would narrow considerably and, assuming differences were still being heard, we could figure out how to narrow the reasons down further so as to understand the phenomena. -Kirk |
Leolewis7 - any insight as to why that is? We're 140+ posts into this topic and a whole bunch of people have said that they absolutely sound differently, but I haven't seen any real theory put on the table as to why this would be the case and I'm still curious. I'm also curious if you, as somebody who hears an obvious difference, has taken the time to compare the copy to the original to see if you have an exact match, or are your experiences based on possibly different "versions" of the same CD? Maybe I just need to upgrade my Pioneer receiver :-) |
Yes it was - hence the :-) |
Well, just to be sure we keep it all straight, nobody has suggested that a CDR could "better" the original CD (aluminum, gold or otherwise) under any conditions. Rather, the basic premise is that you can make a copy of a CD onto a CDR and have the CDR be a perfect bit-image of the original. It's also very easy to make a "copy" that isn't a perfect bit-image of the original. It appears that a lot of people making comparisons between orginal CDs and CDR copies aren't sure of whether the CDR is the former or the latter. It seems safe to say that, regardless of how much difference somebody hears in the perfect bit-image copy vs. the original, that the non-perfect bit-image will sound more different, undoubtedly for the worse. I agree with you that beauty is in the ears of the beholder, and that's what makes this a great hobby. If you place significant value on bits stored on a particular kind of CD over identical bits on another, more power to you. I do have to disagree on the comment about the Pioneer fellow - if he listens to my system and says he hears no difference, I'm gonna tell him he's full of it - my mother could hear a difference :-) Now, if he says the difference isn't worth the cost differential, I'm not going to try to change his mind about that. |
Centurymantra - your post focuses a lot on the transmission / reception of digital data to the DAC, and how the DAC processes it, etc. I'm not clear from reading it if you're suggesting that these problems are accentuated by using a CDR vs. the original CD, or you're just augmenting the general discussion of why people using different equipment might hear different results. If you are suggesting that these other issues are affected by the use of a CDR vs. an original CD, to what do you attribute the effects? Something other than the CDR having different contents than the original CD? I have found that RealJukebox Plus is perfect for creating bit-perfect images of audio CDs on a computer and it takes about 15 minutes plus 8 minutes for each additional copy I want. |
