Probably a touchy subject, but WHY??

Discussion in 'Archived Threads 2001-2004' started by Evan H, Nov 9, 2001.

  1. Evan H

    Evan H Stunt Coordinator

    Joined:
    Apr 10, 2000
    Messages:
    95
    Likes Received:
    0
    Why is there a difference between any two cd/dvd players in audio if you're using them as digital transports only? It would seem to me that a digital signal would be the same coming out of any source, since error wouldn't be tolerated. I mean if a computer cd was read with errors, a program wouldn't run correctly, so how then could error be the reason why an audio cd would sound different? Is there a parity bit in computer cd's that doesn't exist in audio cd's to prevent any error? If that's the case, why wasn't the audio cd made with this in mind? That's the only possible source of a difference I could think of. I guess i'm more confused than anything.
    Thanks for any replies to this in advance, i'm really curious as to why this is.
     
  2. Clinton McClure

    Clinton McClure Casual Enthusiast

    Joined:
    Jun 28, 1999
    Messages:
    4,280
    Likes Received:
    353
    Location:
    Central Arkansas
    Real Name:
    Clint
    My guess would be different equipment = different DACs = (+ different speakers) = sometimes a different sound entirely.
    ------------------
    My DVD Collection Casa del Clint
     
  3. Kimmo Jaskari

    Kimmo Jaskari Screenwriter

    Joined:
    Feb 27, 2000
    Messages:
    1,528
    Likes Received:
    0
    What I want to know is WHY? can't people use descriptive topics in their subject lines? [​IMG]
    ------------------
    /Kimmo
     
  4. Per Berger

    Per Berger Auditioning

    Joined:
    Oct 10, 2001
    Messages:
    6
    Likes Received:
    0
    A short answer, don't have time for a long one right now... [​IMG]
    The file system on a computer cd and an audio cd is not the same. The computer cd has one built for 100% error correction because - as you say - otherwise programs will not run. The disc has sectors, parity and other nice things that looks similar to your hard drive.
    However, an audio cd has all data in one long stream because it must play it all in real time, it cannot stop and reread data. So it has systems/algorithms built in that helps to correct errors on the fly and although not to 100%, as good as it can under the circumstances.
    So this job is done a bit different between different players. One drive might sound better because it has better error correction or does not create as many errors because of a more stable mechanism. Also, you get jitter, i.e. timing errors that are different between different players.
    Any clearer? [​IMG]
    /P
     
  5. Max Knight

    Max Knight Supporting Actor

    Joined:
    May 8, 2000
    Messages:
    531
    Likes Received:
    0
    Per hit it on the head. Below is how this was explained to me (grossly simplified):
    It's easiest to think of the transport as a "pump" that pipes the data to your DAC. Depending on the quality of the pump you are going to get either a nice steady flow or a slightly jerky supply that causes your faucet to sputter a bit (this would be jitter, where the sound doesn't drop out, but changes slightly).
    Choosing a DAC to mate with a transport is much more difficult that I had previously thought. If I were to get a new digital front end now for music, I would probably skip the outboard DAC and go with a high quality player where the DAC and transport were designed together.
    -Max
     
  6. BryanZ

    BryanZ Screenwriter

    Joined:
    Dec 18, 2000
    Messages:
    1,213
    Likes Received:
    1
    Another item that will make a difference is the quality of components used. If cheap ones are used it will sound cheap (Apex). If expensive ones are used, it will sound much better (Marantz). There is another item that may change the sound. That is if the player has tubes (nOrh) in it or is strictly solid state (Technics).
     
  7. Mickey Brown

    Mickey Brown Stunt Coordinator

    Joined:
    Feb 4, 2001
    Messages:
    114
    Likes Received:
    0
    Here is something that makes absolutely no sense to me whatsoever!
    1. We have already determined that PC's read data, and must do so without errors. This is given.
    2. A transport is passing a digital stream, 1's and 0's, nothing else. This is given.
    So from this we can ascertain:
    1. If you bought a $5000 transport you are a moron? You could have bought an eMachine for $500 with a soundcard with digital out that would do the same thing, if not better, because IT CANNOT OUTPUT ANY ERRORS. All the 1's and 0's must get to the source, and IN SEQUENCE.
    I for one just do not understand the concept of 'This $5000 transport that I put on an innertube sounds much better than that $500 eMachine because it has less jitter.' I can understand jitter if you are using the DAC INSIDE the transport (CD Player,) but NOT IF YOU ARE USING AN OUTBOARD DAC!!!
    Someone help me out here.
     
  8. Vince Chan

    Vince Chan Stunt Coordinator

    Joined:
    Aug 22, 2001
    Messages:
    110
    Likes Received:
    0
    I think of it as this way. If you are using the digital out of the CD player, all the player should do is read the raw 0's ans 1's from the CD and pass them to the decoder, which is most likly a receiver/peramp processor.
    SO, theoretically, the series of 0's and 1's coming from cheap CD player 1 should be the same as the series of 0's and 1's coming out of expensive CD player 2. Of course, error correction and jitter does come into play, however, given two different CD players plugged into the same processor using digital interconnect, one should not sound very different from another, since both are ouputting the same series of 0's and 1's.
    Now, on the other hand there are many differences between different decoders, as the have different quality DACs as was said above.
    -Vince
    ------------------
    http://www.arcticcircle.ca/about.htm
     
  9. Saurav

    Saurav Cinematographer

    Joined:
    Feb 15, 2001
    Messages:
    2,174
    Likes Received:
    0
     
  10. AjayM

    AjayM Screenwriter

    Joined:
    Aug 22, 2000
    Messages:
    1,224
    Likes Received:
    0
    The question is does anybody believe that a $69 CD Player bought at Best Buy sounds the same as a $10,000 CD bought at your local hi-end dealer? Assuming of course that you are using the machine as nothing more than a transport? How about you drop the scale a little bit and compared a $150 CD player with a $1500 CD player? I've heard a difference between them, but you are dealing with a semi-complicated setup there, spinning CD, the pickup, and all associated electronics in there. The difference between the 2 machines may be small, maybe the parts in the expensive one is matched down to 5% instead of 20%, etc.
    Sounds like a typical audio situation, the more money you spend the less return you will get.
    Andrew
    ------------------
     
  11. RicP

    RicP Screenwriter

    Joined:
    Feb 29, 2000
    Messages:
    1,126
    Likes Received:
    0
    I hope I just did. [​IMG]
    ------------------
    [​IMG] [​IMG]
    Ric Perrott - My DVD's
     
  12. Martin Rendall

    Martin Rendall Screenwriter

    Joined:
    Dec 5, 2000
    Messages:
    1,043
    Likes Received:
    0
    I think there's something of a scam going on. Money spent on the DAC IS, imho, money well spent. Money spent on the transport, up to a threshold, is also well spent. But after the threshold, you're just throwing your money away.
    Portable disc players have to deal with the transport issue of error correction a lot more than a nice stable shelf model, and they can do it just fine. They tend to have cheap DACs, which is why they aren't good shelf players.
    So, if you invest in a good DAC, you can buy a moderate transport, and have a great system. Good players combine both.
    All IMHO!!!
    Martin.
     
  13. Bill Lucas

    Bill Lucas Supporting Actor

    Joined:
    Mar 20, 1999
    Messages:
    530
    Likes Received:
    0
    There's a reason Meridian uses DVD-ROM and CD-ROM transports in their very highly rated players. As Per said, the buffer allows the correct 1's and 0's to be sent at the correct time.
     
  14. PaulKH

    PaulKH Second Unit

    Joined:
    Oct 3, 2001
    Messages:
    413
    Likes Received:
    0
     
  15. RicP

    RicP Screenwriter

    Joined:
    Feb 29, 2000
    Messages:
    1,126
    Likes Received:
    0
    double.
    [Edited last by RicP on November 10, 2001 at 12:44 AM]
     
  16. RicP

    RicP Screenwriter

    Joined:
    Feb 29, 2000
    Messages:
    1,126
    Likes Received:
    0
    quote: Where the scientific tests demonstrating that 'jitter' is really a problem?[/quote]There's always one. You do know that Stereophile measures every CD player they test for jitter right? Just because you don't understand something, doesn't make it a "crock". One more time for those who don't read: Computer Data and PCM Audio Data are two completely different things. They cannot be compared when it comes to Jitter or digital transports.
    Try these links for starters:
    http://www.jitter.de [​IMG]
    Ric Perrott - My DVD's
    [Edited last by RicP on November 10, 2001 at 01:07 AM]
     
  17. Saurav

    Saurav Cinematographer

    Joined:
    Feb 15, 2001
    Messages:
    2,174
    Likes Received:
    0
    Thanks Ric. That makes how many times those exact same links have been posted on this board? [​IMG] Sometimes I really wish the search feature here worked better than it does.
    Paul, if you're really interested in learning about jitter, go to the website of the Audio Engineering Society (www.aes.org) and search through the research papers submitted to their journal - it's $5 to download them, I think, but that's not too much to pay if you're actually interested in finding out about it.
     
  18. Evan H

    Evan H Stunt Coordinator

    Joined:
    Apr 10, 2000
    Messages:
    95
    Likes Received:
    0
    Wow... this discussion has been rather enjoyable to read... so the answer is a matter of parity error checking bits being used in the Computer CD's that are not present on Audio CD's. Thanks for all the answers to my original question, and i'll enjoy sitting and following this debate as it continues.
     
  19. Saurav

    Saurav Cinematographer

    Joined:
    Feb 15, 2001
    Messages:
    2,174
    Likes Received:
    0
    Evan, try searching through old messages (when the search feature is working) for words like "jitter", "interpolation", "oscillator", and so on - you'll find lengthy and detailed discussions on this subject. After a while, it seems like the same questions keep coming back, and people usually don't feel like posting the same things repeatedly. Which isn't to say that you shouldn't ask questions, but sometimes the same questions have already been asked, so there's a lot to learn by going through previous posts, you might see stuff that won't get covered here.
     
  20. Mickey Brown

    Mickey Brown Stunt Coordinator

    Joined:
    Feb 4, 2001
    Messages:
    114
    Likes Received:
    0
    OK.. I feel as if I have to chime back in here.
    Someone said "Computer Data and PCM Audio Data are two completely different things. They cannot be compared when it comes to Jitter or digital transports."
    I would like to debate this.
    Pop an audio CD into your PC. You can browse each track as if it's data. It IS DATA. How are these different? PCM Audio CD's are simply .wav or .cdx files. The only difference between and audio CD and a data CD is in the way the CD is finished. CD Players look for the track information on a certain spot on the CD. But the data is exactly the same. These aren't analog things were talking about here. I can copy the 1's and 0's and make an EXACT duplicate of the data... In fact, I copied this from one of the articles listed to check out....
    ""If you copy from a jittery source to a hard disk-recorder and later create a CDR from that hard disk, will this result in a jittery CDR? I cannot reach this conclusion based on personal listening experience. In most cases, the final CDR sounds better than the source, as auditioned direct off the hard disk! I must admit it is frustrating to listen to "degraded" sources and not really know how it is going to sound until you play back the final CDR.""
    This relfects to me that PCM cd's and data cd's are no different. The only true difference is in the fact that the PC has a ton of memory in it to buffer and correct jitter, while a standard CD player does not.
    This had been a good discussion.
    I wonder if a $30 budget CD-ROM drive transport with a 256 MB stick of memory would be the best transport money could buy. You could hold half the CD in memory, and jitter could not be an issue. Of course, this 'transport' would weigh about 6 ounces and could not be 'audiophile' quality because it doesn't weigh enough, and would run about $55. I suppose you could stuff a brick in it, and pass it off as BOSE though!
    [Edited last by Mickey Brown on November 10, 2001 at 01:58 PM]
    [Edited last by Mickey Brown on November 10, 2001 at 02:00 PM]
     

Share This Page