Do USB cables make a difference?

July 8, 2018
 by Paul McGowan

10 comments on “Do USB cables make a difference?”

  1. Hi Paul,
    who has persuaded you that people who come from the scientific side are not open to things that are not or only insufficiently proven. Exactly the opposite is true – this is how science works by exploring things that are not or insufficiently proven or rejected.
    Does that mean that you also have to consider statements that are already refuted?
    You know exactly that the USB protocol gives exactly described frame conditions. If a cable is within the required parameters then it will also transmit the data stream as required. Please do not mix again analogue signal transmission with digital transmission. This is two different things.
    As far as the jitter is concerned, I carried out measurements in the laboratory with former colleagues last yearusing USB cables. The results for a 48,000Hz signal was a variation of 0.005Hz, which corresponds to ~ .1ppm. I think that this is not a bad result for an USB 3.1 cable, which costs 15 €.
    Regards

  2. Paul,

    Was it Curious cables from Australia that you were thinking about?

    Bruce

    P.S.
    From one old fart snake oil “believer” to another, keep up the good work.

  3. Paul,

    keep up the good work, the question isn’t whether different USB cables make a difference, they have to (if only at a quantum level). No two differing cables can possibly behave the same way. The question is ‘can I hear the difference’ and ‘am I willing to pay for that difference’. The folks who cry ‘snake oil’ either can’t hear the difference or they simply don’t believe it’s worth the price. Thanks 🙂

      1. Paul, it is interesting that you respond to those posts that confirm your opinion, but not mine. I have shared my observations and really expected a response from you. In the future, if critical utterances or relativizing remarks are not welcome, I can refrain from contributing to the discussion.
        Regards

        1. Sorry, Bernd. I did not mean to snub you. I just didn’t have much to add and did not want to argue. You seem to imply that your studies have shown USB cables to be somewhat impervious to jitter despite their pedigree, something I have found to be untrue. I was not sure I could say much that would bring value.

          Ted Smith has addressed this issue several times in the forums. He knows far more than me. Here’s what he said and it may help shed a little light on alternative ways to express what I am trying to suggest.

          Both amplitude noise and time noise (jitter) can potentially matter. The DS is less sensitive to input jitter than most other DACs so this is less of a problem. But amplitude noise can become jitter and jitter can become amplitude noise any time a clock interacts with the signal (both illustrations are qualitative not quantitative):

          https://discourse-cdn-sjc1.com/business4/uploads/psaudio/original/2X/2/2ba5c209bb8a2311ad1d6a3b5869c9c565787b9c.png

          Any ground loop (which is hard to avoid with non-optical connections can transform the flux in the loop into a current around the loop (and vice versa: noise in a loop can radiate via the ground loop.)

          Any noise that get’s superimposed on any analog signal in a system can become audible: low frequencies simply raise the noise floor, higher frequencies get modulated down into audio frequencies by any non-linearities in the following circuits (e.g. the parasitic diodes in the input transistors, etc.) (E.g. like a crystal radio.)

          Just because an Ethernet connection uses a transformer on each end doesn’t mean that it doesn’t transmit noise: noise near DC is certainly attenuated a great deal but noise near the frequency of the nominal signal frequency passes right on thru the transformer (and hopefully is mostly dealt with by the common mode and differential mode chokes in the Ethernet receiver and transmitter connectors.)

          USB’s noise is a little worse, there is ground noise that’s hard to get rid of, but there’s also noise on the VBUS line (which needs to be there for proper signaling when a device or hub is added or removed.) Also the data lines run parallel to the ground and VBUS lines so there’s more cross talk than one would like.

          None of these issues normally cause any data errors, but when you want 120dB S/N in your audio, the results of any of these effects have to be less than 1 in a million relative to the audio everywhere.

          There are ways of dealing with all of this and various systems will have different needs re. that noise – you’ll find some here who get better sound with Ethernet and others with USB.

          1. Hello Paul,
            I think that you have misunderstood my post, and maybe I misunderstood your post.
            Your headline “Do USB cables make a difference?” implied to me directly the assumption that more expensive USB cables are better than normal price cables. Often enough, pseudo-scientific arguments are cited to sell these extremely expensive cables or it is simply “audiophile lyric”. I wanted to refute that with my measurements. When measuring various USB cables with 3.0 and 3.1 standard, the worst values ​​were 1.4 ppm. This value is still so good that I doubt it could have an audible impact. I also never saw that, for example, guitar strings were tuned with the same precision. It would be interesting to know how much jitter can be induced by amplitude noise and how much amplitude noise can be induced by jitter depending on the USB cable used.
            Anyway – thanks for answering my question.
            Regards

            1. Thanks, Bernd but you did not misunderstand my headline. Some USB cables sound and perform better than others in terms of sonics. WHY they do that is a whole encyclopedic volume of thoughts that may or may not have a lot of scientifically measurable parameters. They should, but then we don’t yet know.

              I can certainly understand and appreciate the work you did measuring those various cables narrowing your search for the one parameter you mention, but it doesn’t yet explain why they sound differently.

  4. The DAC doesn’t care about noise and timing jitter it’s just reading bytes from a memory buffer at a quartz oscillator controlled clock and being TTL digital logic it either recognizes an on or off state nothing in between. According to a professional AES engineer’s lecture that I attended once discussing factors influencing DAC audio quality the most important thing is the stability and accuracy of the underlying clock signal that drives it. By far the biggest factor when listening to digitally encoded music will be the intentional effects of any lossy encoding algorithms like MP3. According to Intel’s USB specifications the maximum cable cable length is 5 meters so that’s the maximum cable length that you can use between your computer to a USB DAC.

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