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Schiit (MultiBit) Bifrost

Discussion in 'Digital: DACs, USB converters, decrapifiers' started by FlySweep, Oct 2, 2015.

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  1. EricR

    EricR New

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    Hope you ordered another set of ears or two as well! ; )
     
    EricR, Oct 8, 2015
    #161
  2. thune

    thune Friend

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    Ultrabike, I apologize if you already covered this. I've been playing around with oversampling filters recently. The easiest 'preserves samples' filter generation method is windowed sinc. You can take your Chebyshev window and multiply it by sinc and get a filter close to the fir1 results but with the property of preserving samples. Likewise you can use kaiserord() to design a filter (around 1/n), but use the kaiser window on sinc instead of using fir1. Again, the results are close enough and you get the 'preserves samples' thing.

    Also, it's easy enough to do a 180k or 1.8M tap oversampling filter on a PC, so optimizing the performance of a limited number of taps isn't so important. Any performance one desires is achievable.


    h = fir1(18000, 0.5, chebwin(18001,180));
    win=chebwin(18001,180);
    h2=gen_windowed_sinc(win,2);
    h2=h2./sum(h2);
    plot(20*log10(abs((fft([h' h2])))));
     
    Last edited: Oct 8, 2015
    thune, Oct 8, 2015
    #162
  3. The Alchemist

    The Alchemist MOT: Schiit - Here to help!

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    My suggestion in an earlier post was Multifrost as well.
     
    The Alchemist, Oct 8, 2015
    #163
  4. Eric_C

    Eric_C Friend

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    I dunno, "Bifrost Multibit" seems to stick for me, especially after Gungnir Multibit was explained to me.
     
    Eric_C, Oct 8, 2015
    #164
  5. Judeus

    Judeus Facebook Friend

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    I hope schiit releases two things:

    1. Some sort of optimized transport with an aes/ebu out and with a web app to control it, built in 2.5" drive support <$1000

    2. exotic end Game tube amp to compete with eddie current, cavalli, etc <$2500

    a nigga can dream
     
    Judeus, Oct 8, 2015
    #165
  6. ultrabike

    ultrabike Measurbator - Admin

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    Awesome sauce dude!!!

    Indeed, if you read section C of "A Digital Signal Processing Approach to Interpolation" (< click on linky), this condition corresponds h[0] = 1 and h[n] = 0 for all n = +/-L, +/-2L, ... +/-[(N-1)/2L]L, which basically imposes a sinc window.

    In section D, the authors discuss (among other things) applying this constraints. The result was a slight increase in ripple in the passband and the stopband when applied to Parks-McClellan optimal filters if I'm reading the paper correctly. Obviously this will not show in comparing input and output samples aligned in time, but it would be a (smallish) degradation in the interpolation itself.

    Ran your code and it does what it supposed to.

    With the filter you propose (1001 taps version) I get about -207dB of error power (input vs output). And here is the frequency response:

    ChebySinc.png

    Note that the more samples, the better the interpolation quality, regardless of the input = output restriction.
     
    ultrabike, Oct 8, 2015
    #166
  7. rayfalkner

    rayfalkner Not to be confused with Roy Fokker - Friend

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    Voting for Bifrost Multibit too.
    It is a cute nick. If only I'm good with custom jobs, I'll makeover the chassis into something resembling a scene like this:

    [​IMG]
     
    rayfalkner, Oct 8, 2015
    #167
  8. Cspirou

    Cspirou They call me Sparky

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    They would only do an end game tube amp if its a hybrid or OTL since they don't want to mess with transformers.
     
    Cspirou, Oct 8, 2015
    #168
  9. ultrabike

    ultrabike Measurbator - Admin

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    They did tubified Mjolnir 2...

    I propose Biffy - pronounced beefy - (the Anti-Porky).
     
    ultrabike, Oct 8, 2015
    #169
  10. Judeus

    Judeus Facebook Friend

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    ya the tube amp is a long shot, i think it's too niche for them which is totally fine.

    I think they could pull off a good transport though.
     
    Judeus, Oct 8, 2015
    #170
  11. The Alchemist

    The Alchemist MOT: Schiit - Here to help!

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    ahh!!!! I want the multibit upgrade for my Bifrost Uber! Gonna have to wait to get some money :(
     
    The Alchemist, Oct 8, 2015
    #171
  12. lm4der

    lm4der A very good sport - Friend

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    Don't forget beef roast and beer fest.
     
    lm4der, Oct 8, 2015
    #172
  13. AustinValentine

    AustinValentine Friend

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    I was always partial to Beefroast, if only because it imparted the appropriate amount of delicious living. It's a DAC that Nick Offerman would buy.
     
    AustinValentine, Oct 8, 2015
    #173
  14. lm4der

    lm4der A very good sport - Friend

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    Personally I like Beerfest, because... well... beer. Just sayin'
     
    lm4der, Oct 8, 2015
    #174
  15. SeaBupter

    SeaBupter Friend

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    MultiBite BeefRoast
     
    SeaBupter, Oct 8, 2015
    #175
  16. lm4der

    lm4der A very good sport - Friend

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    Multi burp beerfest. Sorry, had to...
     
    lm4der, Oct 8, 2015
    #176
  17. The Alchemist

    The Alchemist MOT: Schiit - Here to help!

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    aww..I was hoping to start the new nickname for the Bifrost Multibit - I was hoping people would adopt the Multifrost. :(
     
    The Alchemist, Oct 8, 2015
    #177
  18. Tuco1965

    Tuco1965 Suffring from early onset Alzheimer's - Friend

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    I like either Bifrost Multibit or Multifrost.
     
    Tuco1965, Oct 8, 2015
    #178
  19. lm4der

    lm4der A very good sport - Friend

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    Ok, I don't want to see The Game feeling disappointed - in his honor I will put aside my dorkyness and support Multifrost.
     
    lm4der, Oct 8, 2015
    #179
  20. SeaBupter

    SeaBupter Friend

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    Ah, the OktoberFrost.
     
    SeaBupter, Oct 8, 2015
    #180
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