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Schiit Happened: The Story of the World's Most Improbable Start-Up

Discussion in 'Jason Stoddard' started by jason stoddard, Jan 23, 2014.
  1. jimmers
    Thermometer DACs are more linear (and as @soekris mentioned paralleling resistors reduces noise) and the resistor differences tend to average out, unfortunately while a 20 bit R-2R ladder DAC is self-decoding and requires ~ 20 switches and 40 resistors (mono), a 20 bit thermometer DAC needs ~ 1 million switches and resistors and the decoding from binary to thermometer is not included, see below for a 4 bit version of a decoder, there are frames titled - 2bit DEC, 3bit DEC and the full picture - 4bit DEC
    As you will notice for each new bit frame moving to the right a new level of decoding is added and the number of outputs is doubled, continue for another 16 levels and ~1 million outputs and you have your 20 bit decoder to operate your million switches and resistors.
    You'll need 4 of those for a balanced 20 bit DAC :grimacing:
    That's why it's only done for 6 bits in Yggy's chips.


    By using a thermometer DAC for the 6 MSBs the errors in the R-2R DAC are pushed down 36dB

    (well that's my take on it)
    Last edited: Feb 10, 2019
  2. golfbravobravo
  3. golfbravobravo
    No-one expects the $20K of audio jewelry...............

    Or red uniforms.......
  4. valiant66
    Look at the Oracle Delphi for an example of a turntable with a y-shaped chassis that has a conventional looking dust cover. No comparison pricewise, of course,even used,


    Other technological differences too.
  5. earnmyturns
    Archimago asks good questions, and super-duper clocks for Ethernet and USB audio -- both async protocols -- is magic beans, but he's never addressed properly, in that posting or earlier ones, the question of electrical noise carried by USB wires (or other digital electronic) sources into DACs. The "bits are bits" dogma works fine for reasonably designed purely digital circuitry, but it falls apart when the bits, electrically encoding as noisy signals go into controlling the generation of an analog signal with a dynamic range > 100dB, meaning < 20uV relative to a 2V 0 dB output level.
  6. valiant66
    I read earlier in the thread it’s $35.
  7. rkw
    For those of you who are not on Windows today and might miss this, a cool Bing wallpaper.

    Electron microscope image of stylus on record, for the occasion of the Grammy Awards today.

  8. ScottFree
  9. alpovs
  10. alpovs
    The discussion was not about hardware upgrades. It was about firmware updates.
  11. alpovs
    Yes, I realize that an n-bit thermometer DAC requires 2^n resistors. This Wikipedia article helped me understand better what you said: https://en.wikipedia.org/wiki/Resistor_ladder#Accuracy_of_R–2R_resistor_ladders
    "Small inaccuracies in the MSB resistors can entirely overwhelm the contribution of the LSB resistors." "Resistors used with the more significant bits must be proportionally more accurate than those used with the less significant bits" "The required accuracy doubles with each additional bit"
    So, they increased the accuracy by going with this R-2R/Kelvin design. For such a high bit count it may be the only way.

    Regarding the discrete R-2R DACs the article states: "For a 10-bit converter, even using 0.1% precision resistors would not guarantee monotonicity of output. This being said, high resolution R-2R ladders formed from discrete components are sometimes used, the nonlinearity being corrected in software."
    Last edited: Feb 10, 2019
    golfbravobravo likes this.
  12. porchwizard
    I think it's cool as schiit. Thanks for the pics!
    ScubaMan2017 and Rensek like this.
  13. jimmers
    I hope my spiel helped you get your foot in the door of segmented DACs.
    The Wikipedia article doesn't include thermometer DACs (outside the article scope) and the profusion of simple gates required for it, something in the order of 2 * ((2^n) - 1)

    p.s. Soekris higher end DACs (and the DIY dam1021-12) use discrete 0.01% resistors, but I don't know what else he does to get 24+ bit monotonicity.
    Last edited: Feb 10, 2019
  14. soekris
    The keyword is Sign Magnitude.... That way you get level precision down to the last bit, which is what you really need for Audio....
    Last edited: Feb 11, 2019
    CAPT Deadpool likes this.
  15. jimmers
    Thank you,
    I thought that was only to avoid possibly big glitch around analog zero.
    Spoiler edited, it was a waste of words. :head_bandage:
    Last edited: Feb 11, 2019

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