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need help upgrading USB cable

Discussion in 'Computer Audio' started by cb3874, Jan 18, 2012.
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  1. PleasantSounds
    I can't believe I'm getting drawn into this discussion, but anyway....
    The quoted statement is true, provided that all the 0's sent by the source are interpretted by the receiver as 0's and all the 1's as 1's. Then we have perfect digital transfer, and indeed it doesn't matter where in the chain we interpret it - it's always the same. Life would be sooo good if that was all that there's to it :)
    Unfortunately, there's no such thing as digital data transfer - the signal is only interpretted as digital, based on some protocols or conventions that both sender and receiver understand. The irony is that the physical connection between the two devices is analog.  Based on the convention, the receiver detects increases and drops of the voltage on the line at specific time intervals, and quailfies them as 1's or 0's.
    Once we understand that, it's not too hard to imagine how certain interferences can create problems with this transfer - anyone who ever listened to a short wave radio knows what I'm talking about.
    The digital world is pretty clever though - the voltage differences between 1 and 0 signals are large enough to ignore the impact of most garbage that would totally destroy any analog transmission; there are checksums that allow detecting transmission errors; there are redundant protocols that transfer the data correctly even with certain percentage of errors; there is handshaking which allows to re-send the corrupt data packages. In other words: it should be flawless.
    The only aspect that could shake this nearly perfect world is timing: if the data cannot reach the destination in time to be processed, we're going to hear it.
    Having said all that, I can imagine some situations in which a quality USB cable may help:
    - in the engine room of a nuclear powerplant
    - within 200m radius of a TV transmitter (OK - I'll allow mobile transmitter stations as well)
    - under a high voltage powerline
    In all other situations, if you hear difefrences in the warmth of the tone or tighter bass with one USB cable but not another, it's only because God makes it so.
  2. Currawong Contributor
    I suggest to people nowadays they buy a Vaunix hub, which costs about the same as some of the more expensive USB cables but provides a higher quality source of power than a computer's USB port.
  3. ultrabike
    The way I understand it is that in digital communications the transmitted waveform may be analog, but the information transferred is binary (digital.) Like you said, the analog waveform is typically subject to noise, inter-symbol interference, spurs, jitter, wander, and so on. There are bit error (BER) performance curves as a function of SNR for different well known digital communication schemes.
    Indeed, standard's compliant USB cables should meet a certain set of BER performance requirements (with certain test equipment.)
    Not sure about the tone or tighter bass, but I have heard some dudes saying that some USB cables provide superior sound stage... [​IMG]
  4. I3eyond
    When I was running PC>DAC via USB I did get some noise.
    I picked up a Musical Fidelity V-Link.... ran optical into my DAC from the V-Link...BAM!  Noise was gone.
    Optical offers galvanic isolation, which, IMO, is a must for any computer setup.  Computers are noisy by nature!
  5. ultrabike
  6. I3eyond
    Musical Fidelity V-DAC
  7. glavewu
    I think our cell phones also utilize digital signals, but why it has noise heard? This example may be too extreme but no matter copper silver or air, they are just media to carry the signal. Digital or analog only depends on how you process it. Digital communication system has better ability to avoid noise doesn't mean it can't be interfered. When you use USB to transfer data like files, it will keep authentic because there are ways to check the data, if there are some errors it will be corrected by means or at least can be resent. But for audio streaming, there is no chance to correct the signal or resent anything because it must be real time (has buffer of course but can't be infinite long) otherwise you will hear it. 
    I'm not saying the better cable will definitely have noticeable difference because the copper as a signal media is already good enough, the possibility to have a 0 get interfered to be regarded as a 1 is really low. But in certain circumstance, it may have noticeable sound. At least the better cable does have better ability to avoid noise.
  8. PleasantSounds
    The sound quality in phone communications is much worse due to compression and quantization. Your CD player outputs upwards of 800 kbps - compare that to a phone conversation that can get as low as 1.8 kbps. 8 bit depth used by telephone transmissions also has much more quantization noise than your usual CD, or even your typical MP3. This has nothing to do with the media.
  9. glavewu
    You are right about the coding but if there are no noise introduced by the media, we should at least hear constant and clear low quality sound (means even though the sound quality is low, we should receive the same low quality sound as when it was sent). But in fact we usually hear some glitches or even worse some piece of voice just can't be heard when signal is bad, in other words, too much noise comes from media. The high fidelity in words just means what we get is exact as possible as the source. It has nothing to do with the sound quality. If the source suck, the hi fi system will make it even more noticeable. So a good USB cable at least still contributes to the term of high fidelity, though I'm not sure it is noticealbe or not. Some people may have more sensitive hearing than others, but do some tests to tell.
  10. glavewu
    My bad, hi fi system in term should include a high quality source... I should say the communication sub system in hi fi system, like we use USB to transfer signal from computer to external DAC. That part has nothing to do with sound quality, its job is just to transfer signal as high fidelity as possible, so any means to deduce noise contributes to the term of high fidelity.
  11. PleasantSounds
    The glitches you are referring to in phone comms are most likely signal dropouts. 
    As far as I can tell there are two conceivable situations where a USB connection may have some impact on the audio quality:
    1. Because it is creating a galvanic connection to another device (i.e. PC), where the ground level does not have to be as clean as in an audio device. But better or worse cable won't matter in this case - you need a USB isolator like this.
    2. Some DACs are powered from the signal source - their performance may be impacted by the cable quality. If the power lines in the USB cable are too thin, cable is too long or made from a wrong material, possibly the resistance could cause some power starvation in the DAC. In this case a cable with better conductance may help.
  12. KT66
  13. itchyears
    Think ill go against recommending a $1 usb cable from the pound shop :wink:
  14. fluidz
    All usb cables sound the same to me.
  15. yay101
    I read a really nice write-up on "how" in.... stereophile or sixmoons... Cant remember. If i find it will let you know, it has a lot to do with how digital music is sent over the cable and the "square" signal not translating properly from one end to the other, especially as cables get longer.
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