Phil Leigh;215495 Wrote: > Actually that's not quite true - it is an analogue representation of a > digital signal and so there is some work to do at the receiving end to > recover a true digital signal.
Well, so much for keeping simple for the poor guy. Yes, if one wants to delve that deeply into the subject, every form of electronic transmission uses modifications to the wave of the signal passing through the transmission media/cable. However, what we are referring to is how those fluctuation's represent the data. You sound very well educated so I will just try to further explain what I meant to the poster in case it incurred confusion. I'll try to avoid explanations of voltage vs. current, vs. frequency, etc. Analogue (as used in home sound equipment) When sound signal is sent from a player device, like a CD player, in an analogue format, every sound frequency is represented by a matching fluctuation in the electronic signal passing through the cable. This is the same type of signal that your speakers need to receive in the end because speakers convert these exact fluctuations back into the corresponding sounds. Because these each fluctuation exactly represents a sound level/frequency, minor discrepancies in these fluctuations make a difference. This makes an analogue transmission much more susceptible to any outside interference or physical issues with the cable itself.. Digital Signals (as used in home sound equipment) When audio is recorded digitally, the process takes the analogue signals from the microphones and converts each 'sound' (so to speak) into a number. The media stores these numerical representations of the sounds. Exact duplicates of this recording can easily be reproduced because you just have to duplicate the numbers. When you play a CD and send out analogue signals, the numerical data on the disk passes through a "DAC" or 'Digital to Analogue converter'. The transmission is then sent as described above. However, if it is sent to the receiver in digital format, it doesn't go through the DAC and the exact numerical data is sent to the receiver. It is then up to the receiver's DAC to convert it to analogue before it hits the speakers. Again, fluctuations in the electronic signal passing through the cable are used to represent the numbers but...... -- There is some headroom in the levels of fluctuation before a number actually gets misrepresented. This makes it less sensitive to outside interference to some degree. -- The biggest reason why the sound quality is safer is that when sending numbers digitally, something called error correction can be used. To over simplify, If the far end doesn't get 'mathematically, what it expects to get, the data simply gets resent. For tiny discrepancies or loss, this happens fast enough that there is no discernible sound loss or change. Thus my statement that unless something in the system is so bad that the sound data just doesn't get there, the quality should be exactly the same for fiber or Coax. Can Digital still go wrong? Yes, but normally in a much different way. --With Analogue, some physical properties of the cable (it's too thin for the particular usage) and outside interferences can change the nature of the sound you here. This can cause you to hear changes in sound quality, tone, static, hum, almost anything actually. --With digital, normal circumstances result in an exact numerical copy of the CD reaching the receiver. However, a loose cable, a damaged cable or even a cable bent too sharply can cause data loss. This usually causes jitter, chirps, or complete sound loss as opposed to changed sound tone or quality. Can the two sound very different even if both are working perfectly. Yes, the thing to remember is that most modern receivers can run all sorts of sound modifying modes on digital data. Because it's numbers and can be manipulated mathematically, you can do a lot more to the sound than just adjust the bass and treble like on older receivers. This is why you will see many 'sound modes' listed on most receivers, ie. stadium, club, rock, disco, etc. Even if you feed the receivers with a plain old analogue signal, the receiver can and might be converting that analogue signal to digital so it can apply these 'modes' before reconverting it to analogue again to hit the speakers. One has to be conscious of all these things to make sure you are comparing apples to apples. So which is better, digital or analog? It can be a matter of personal choice but generally if you are playing a CD or DVD or other digital media, a conversion from digital to analogue has to happen somewhere before it hits the speakers. -- Some would say that most DACs are created equal so best to have the conversion done as close in the system to the speakers as possible (normally meaning go digital from the player to the the receiver) to avoid higher chances of signal modification or degredation. -- Another camp might say, use the device that has the better quality DAC. (Again, this is normally considered the receiver but many will tell you that if it's not applying 'modes' there is little to no discernible difference in most DACs as it's just converting frequency to numbers.) Soooo Back to the point. Which is better for digital transmission, coax or fiber? --From strictly a sound point of view, in a normal home audio operating environment, neither should prove superior to the other. Tales of coax sounding "warmer" and "more pleasing" over the "Sharpness" of optical cable are completely false. Unless there is a bigger issue, both are sending the exact same numerical data to the reciever. However.....Some physical things to consider between the two. 1. Optical uses uses frequencies of 'light'. It is after all using a laser. Coax uses frequencies electrical frequencies. Both end up doing the same thing but this makes the coax more susceptible to outside electrical interference. However, the design of coax makes it a "shielded" cable. That is to say it is very resistant to outside electrical interference. 2. On the other hand, fiber is more susceptible to damage and sharp bends that can disrupt the signal or even render the cable useless. Also, the quality of the ends and the terminals they plug into mean they are more susceptible to falling out or getting loose. Neither is normally a problem if things are not moved around much. 3. Coax is much easier and usually cheaper to run over long distances like from one floor to another, if need be. I can't remember the distance limitations of TOSLink but it wouldn't be my first choice to fish through walls unless it's done prior to getting sheeted in. Ack, I can't believe I wrote all that. I could have posted a link to somewhere that explains it better, I'm sure. Anyways, Yes, you are correct at a very deep level, but in this application of home audio, I was trying to make a point without going too deep. -- Murph ------------------------------------------------------------------------ Murph's Profile: http://forums.slimdevices.com/member.php?userid=10553 View this thread: http://forums.slimdevices.com/showthread.php?t=36667 _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/lists/listinfo/audiophiles
