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USB cable supposedly improving DAC sound quality? How can I take other posts seriously after that?

Discussion in 'Sound Science' started by mus1cjunk1e, Mar 26, 2011.
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  1. robertbudding
    The signal is interpreted as a 0 or a 1. All that is required is that the signal is clear enough to be interpreted. And any problems can be easily identified by comparing the resultant bit stream. And their are algorithms to ensure accuracy. If your expensive cable is better, then it can be measured.
    Last edited: Dec 21, 2017
  2. robertbudding
    A statement without experimental support is completely meaningless.
  3. gregorio
    1. Then you're saying all your equipment is inferior to amirm's tested system of standard laptop, generic USB cable and $129 Topping D30 DAC because with that system you couldn't have found USB inferior to anything because the artefacts from USB system are well below audible, as you yourself have ALREADY agreed!
    1a. Again, obviously not as good as amirm's relatively cheap system which has NO audible USB artefacts and therefore can't sound inferior.

    2. If you really can hear the difference between USB cables, you've got a seriously screwed/faulty system/DAC. It's obviously performing about at least 100 times worse than amirm's test system with a generic USB cable! Ouch, I hope you spent way less than $129 for it?
    2a. If you really are hearing such differences then you "have to believe they put considerable" incompetency into their USB implementation!!!

  4. amirm
    Harmonics as the name indicates, will be multiples of the our signal source. If we had such, they would then occur at 24 Khz, 36 Khz and so on. Importantly, they would never be any components at lower frequencies than our tone at 12 Khz.

    If you look at my graph, you see symmetrical spikes on both sides of our main tone. When you "jitter," i.e., mess with the timing of the clock DAC, in frequency domain, you get sidebands at +- of the frequency of jitter. Let's say there is a sine wave inside of the DAC at 1 Khz. If that bleeds into DAC clock, then you would get components at +-1 Khz relative to our main tone which means "spurs" at 11 Khz and 13 Khz (12-1 and 12+1). You can read more on this topic in one of my articles: https://audiosciencereview.com/forum/index.php?threads/a-deep-dive-into-hdmi-audio-performance.56/. Here is an example from that article:


    Those two tiny spikes are symmetrical relative to our 12 Khz tone, telling us they are jitter (they can also be reference voltage modulation but for the purposes of this post, they both manifest themselves the same way).

    So anytime you see spurious tones hugging each side of a single tone, it means some kind of jitter, not harmonic distortion.
    Last edited: Dec 22, 2017
    SeeHear likes this.
  5. amirm
    You are explaining an idealistic system. Real systems will extract the bits just fine as you say, but then must have a moat around that digital input to make sure none of it bleeds into a) analog output of the DAC b) the DAC clock and c) the DAC reference voltage. When you don't do that, the digital input indeed bleeds and changes the output of the DAC even though the bits are extracted correctly. Using my last article I referenced, let's look at the output of the DAC inside an AVR when using two different digital inputs: S/PDIF and HDMI:


    As we see, the analog output of the DAC changes distinctly (for the worse with HDMI in red) even though bit extraction is the same and correct in both cases.

    Think of this as road noise in front of your house. Without sufficient isolation, the noise will bleed into your home. Same here.

    Fortunately as I have mentioned USB for the most part is implemented very well. Just watch out for exceptions such as Schiit Modi 2.


    Here is the same signal driving two other low-cost DACs:

  6. robertbudding
    I’m still awaiting links to a double blind listening test, matched to 0.1 dB, to support the claim that any of this is actually audible.
  7. amirm
    Level matching? Why would the level change with USB cable swaps? Of digital inputs for that matter?
  8. Mediahound
    Worth watching for more actual real world experience on the subject and not just theoretical in the lab armchair hypothesizing:

    Last edited: Dec 21, 2017
  9. GChief
    I guess that would be my point in every post I make. I have been doing this for 40+ yrs. The time frame is a guess but I chased numbers and measurement from 1980 thru about 2000 then finally saw the light and realized that all those measurements are just for making an educated guess. It’s all about synergy and how it sounds to you. Eventually the light bulb goes off with audio.
  10. amirm
    He said he conducted 16 blind trials. He says both he and the person doing the switching took notes. But we are not given that data. Just says he was right. What to make of that? If I get 10 tries let alone 16 right out of 16, I would be shouting that number out loud. :D Leaving it out makes one wonder.

    I am confident if I ran that test, he would fail it and fail it bad. I am willing to put $2,000 forward if he wins it. He should pay me $500 if he loses so that I can make more measurements that anyone can repeat. :)
  11. amirm
    I don't know about the former but the latter is definitely so. That's why when we want reliable answers, we make sure nothing but your ears are making those judgements. You shouldn't need anything else, right?

    Let's take a test as easy as speakers where we all know they sound different. So bias should not come into play but it does in sighted evaluations: http://seanolive.blogspot.com/2009/04/dishonesty-of-sighted-audio-product.html


    See how the ratings of speakers revers ("S" and "T") when we performed the same test blind versus sighted. Again, this is with speakers where we think the sound difference is so large and distincts that we can just "trust our ears." Well, we can't because we are biased on my extraneous factors such as cost, looks, even colors.

    Controlled tests are a lot harder and more expensive than sighted casual tests we all do. Yet it is the only type of listening test that is accepted by our most respected research and engineering organizations (ASA, AES, IEEE, etc.).

    Of course as individuals we can all choose to keep using sighted tests. The only issue is when we try to champion them to others as in this thread. Then, you get confronted with having to demonstrate their validity and how the entire professional communities focused on this field are stupid and ignorant.
    Last edited: Dec 21, 2017
  12. GChief
    I don’t disagree. I have just be doing this awhile and when I was younger I got caught up is the whole numbers matter thing. They do matter but just for making educated decisions. I have paired many things togeather that should not of sounded as good as it did. My current home set up is one of those. It punch’s way above it’s weight class if you go strictly by the numbers. Your first paragraph in your response to mine is basically saying the same thing, let the numbers guide you but at the end of the day it is how it sounds to you, the numbers don’t mean crap at that point. What you like does not mean the next 10 people will agree no matter what the spec sheet says.
    nick n likes this.
  13. GChief
    Sorry didn’t know you couldn’t say crap in here
  14. bigshot
    Have you tested it with a Mac? I'd be interested if it has the same problem. The problem may be the computer or kind of computer, not the DAC itself.
    Last edited: Dec 21, 2017
  15. castleofargh Contributor
    no. ^_^
    there are those things like hearing threshold, and masking. something has an impact, well everything has an impact when we forget about magnitudes. what concerns us is to know if it's big enough to be audible and if it is, how to avoid it. getting paranoid about any small stuff without regard for magnitudes might be entertaining to some audiophiles, but it doesn't mean it's actually audible for that audiophile.
    now if we end up with circumstances where it is audible, fine, but that must be ascertained properly. not with what I've come to call the anti scientific method: get a feeling or an idea, then look for anything that will agree with it. which is a quest for self justification, not a quest for facts. and the difference is "night and day"!

    I have no preference in the conclusion, only an opinion based on my own experience and knowledge. and I don't think everybody who doesn't have my experience is full of crap. I'm always ready to make a new conclusion when evidence I can trust is presented to me. something the average cable believer fails to do with a consistency that is almost making a point on it's own.
    all I want are testimonies where what counts is the sound(measured or heard), instead of the look of the cable, the price tag, and how some friend described the improvements to expect from that one cable he's so fond of. to get that, we need proper listening test or measurements.

    you're describing how I pick my desert, not how we make sure that a USB cable is causing an audible difference or by how much. you realized that your personal preferences don't necessarily align with objective fidelity. good for you. but it concerns you, not the gears. what you prefer doesn't have to be the best, it doesn't even have to be what other people will prefer. so it's a very important notion for yourself, and a very irrelevant notion for everybody else. that's why we try to stick to more objective data in here, because the one notable perk of objective is that it doesn't change in somebody else's hands. which makes it great for sharing information about gears on a forum IMO. and alone at home, I go with my guts and keep what I like for whatever reason, objective or not, same as for my desert ^_^.
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