Massdrop x Grace SDAC Measurements

Discussion in 'Source Measurements' started by Marvey, Sep 12, 2017.

  1. Marvey

    Marvey Loves sex and records

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    Figured I'd post these since Jude is bragging about his AP555. Noise floor is higher here because I'm using a balanced probe with a /10 divider (less spurious garbage, but at the expense of moving the noise floor up 10db). I wouldn't worry about it because really, anything under 100db from the main signal... yeah, only John Atkinson cares to interpret stuff like that. It seems like a good night tonight for measurements (that's how HARD they are to do and get consistently - so many environmental factors can screw things up). I'm also running it through a Wyrd, because the Wyrd provides cleaner power and has the current capacity of the USB spec, which is something computer makers don't always meet.

    BTW 1kHz measurement here. Something not available at HF.

    SDAC 1kHz.png
    SDAC 20kHz.png
     
    Last edited: Sep 12, 2017
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  2. Marvey

    Marvey Loves sex and records

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    Zoom in on 1kHz and below. Fairly clean with no 60/120Hz spikes, although I'm seen crap at 60/120Hz come and go with other DACs. Again, getting good environmental conditions tonight.

    SDAC 1kHz and below.png
     
  3. Marvey

    Marvey Loves sex and records

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    19kHz, including wideband measurement to 50kHz

    SDAC 19kHz wide.png
    SDAC 19kHz.png
     
  4. Marvey

    Marvey Loves sex and records

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    19kHz and 20kHz
    SDAC 19kHz and 20kHz.png
    [​IMG]
     
  5. Marvey

    Marvey Loves sex and records

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    -90.31db 1kHz tone. 16-bit data.
    SDAC 90db 16bit.png

    Yup, looks right to me with the steps, since -90db is a toggle of the LSB. Is there some dithering going on? (made sure it was turned off in software).
     
    Last edited: Sep 12, 2017
  6. Marvey

    Marvey Loves sex and records

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    Here's the same signal, but using 24-bit data.
    SDAC 90db 24bit.png

    This is consistent with the measurement on HF.
     
  7. Marvey

    Marvey Loves sex and records

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    Still scratching my head on the one above because the Modi 2 24-bit -90.31db signal looks like this:
    Modi 2 90db 24bit.png
    Modi 2 24-bit -90.31db 1kHz

    Wondering if this is because of something going on with the SDAC: XMOS, XMOS Windows drivers, dithering, or that the AKM4452 isn't quite as good as the AKM4490 (Modi 2). Either way, I wouldn't stress about it, unless you have a lot of hires content. And even if you do have hires content, it could be mastered like shit and sound MUCH worse than 16/44 - see here: http://www.superbestaudiofriends.or...ul-simon-diamonds-on-the-music-analysis.4050/

    Tells you how fricking deaf most audiophiles are.
     
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  8. Marvey

    Marvey Loves sex and records

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    Lastly, here is 1kHz using the high precision Focusrite 2i2 (balanced inputs) which has a 25db lower FFT noise floor than the QA400 and /10 balanced probe. For those of you who can hear harmonics 110 to 130db below the fundamental.

    SDAC 1kHz Focusrite.png
     
    Last edited: Sep 12, 2017
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