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Supra USB cable and my findings/predictions!

Discussion in 'Sound Science' started by manueljenkin, Nov 27, 2019.
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  1. gregorio
    @manueljenkin Your post appears to be based on a number false assumptions, misunderstanding of digital audio data, subjective aural perceptions and the fallacy that if some people independently report the same subjective aural perception the cause must be some objective aural effect. For example:

    As you state, the USB protocol includes considerable error correction because it allows for very high data transfer rates and a single bit error can be catastrophic. A single bit error could cause a transferred program file to (for example) reference an incorrect memory location and crash. However, 16/44 digital audio data requires less than 1% of the max transfer rate of USB 2.0 and with interpolation error correction, any error (if there is any) would occur in the LSB, which is just noise (random 0's and 1's) anyway and pretty much the opposite of catastrophic, IE. Irrelevant and inaudible. Hence why more sophisticated error correction isn't used for digital audio data. In fact, pro audio devices are capable of running more than 30 simultaneous 16/44 channels of digital audio data over USB 2.0, with no detectable errors.

    It's relatively simple to compare the impact of different USB cables. Simply choose a music track, loop-back the output of a USB DAC to an ADC and record it, then rinse and repeat with exactly the same track and equipment, just changing the USB cable. Finally, use the (freeware) Audio Diffmaker to time align and analyse the difference between the two recordings (USB cables). It's relatively cheap, quick and easy, and eliminates the need for a whole bunch of assumptions and subjective perceptions/impressions!

    G
     
    Last edited: Nov 30, 2019
    bfreedma and SoundAndMotion like this.
  2. manueljenkin
    Thanks a lot. Answers like this is what I was waiting for. . I'll do that when I get access to an equipment that can do that. Any way I could do it using my focusrite 2i2?
     
  3. gregorio
    Sure. The 2i2 certainly isn't perfect but it doesn't need to be, any artefacts it has will be the same on both recordings (of the different USB cables) and therefore will not show-up as a "difference". Obviously, ALL the settings would have to be identical for both recordings, you only want to measure the difference a different USB cable makes (or doesn't)! Here's the link to Audio Diffmaker: https://www.libinst.com/Audio DiffMaker.htm

    G
     
    SoundAndMotion likes this.
  4. SoundAndMotion
    There are some known limitations of Audio Diffmaker. Paul Kane has recently developed a similar, but vastly improved app, called DeltaWave (link). It is described and discussed
    here and here. Paul responds to questions, bug reports and feature requests.
     
    gregorio likes this.
  5. manueljenkin
    Thanks a lot. Now this starts looking more like a science forum, i made the mistake of pushing in my subjective opinions on it instead of being straight forward with my question. My oscilloscope is also coming in so I can do more testing as well. Foobar vs winyl was measured and the difference, atleast in the asio configurations of the two are profound even audibly. My friend is testing other tones, I've sent him, so once he returns back with his findings, I'll post here (i dont have an oscilloscope at the moment). I've tried multiple windows reinstalls with same effect on Foobar vs winyl.

    Btw. I worked as a design validation engineer at a VLSI company for over one year. I have validated interfaces that communicate to i2s/pcm slaves, apart from validating other buses like ahb, axi, etc as an RTL (that's like the very Idealistic initial model without transistor set-up/hold timing properties). I haven't handled phy layers though I did have very short experience in physical design as well. I'm not saying that I know everything (this is a sea and what I've touched is only a tip), there's tonnes of things, clock domain crossing, clock skew, etc.. and it's just impossible to measure everything. I was trying to actually undestand what is exactly happening during audio transmission internally.

    I'm also getting my measurement rig ready and I am working on like 9 personal papers in parallel atm on headphone transients parametrization. This cable thing, i wasn't expecting anything, but the feeling of an audible change (regression for the most part ) made me curious. I'm always happy to be proven wrong, if it means I learn something. As i mentioned in earlier comments, high fidelity audio is not really my cup of tea, I'm just trying to learn. I actually prefer playing an instrument myself than listening to a recording someone else made.

    This was one of the papers I made some experiments on using presonus mics that i bought : https://www.google.com/url?sa=t&sou...FjACegQIBxAB&usg=AOvVaw05rInbhwjEK3zwsgDDI3k9
     
    Last edited: Nov 30, 2019
  6. SoundAndMotion
    FYI, @gregorio earned your gratitude with his advice. I just suggested a different app.
     
  7. castleofargh Contributor
    I had missed this, thanks. Audiodiffmaker has been such a great help soooo many times for me over the years, but it does have a number of limitations depending on what we hope to show. If the clock drift option for files recorded with different dacs works well, it would already make this app worth using. And the other features look interesting, including a more informative report. Can't wait to fool around with it \o/
     
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