Field guide to determining Modi MB or Bifrost MB v1 or v2 firmware

Discussion in 'Source Measurements' started by atomicbob, Jul 16, 2018.

  1. gixxerwimp

    gixxerwimp Professional tricycle rider

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    Thanks for the math lesson @atomicbob. Makes sense now why my amplitudes are lower than yours with my Realtek codec.

    I'll make one last feeble attempt to plea my case. The four sine waves hidden in the noise of my -90dB trace, and the lack of clear "spikes" at each zero crossing of my -70dB trace aren't evidence of v2? Or I guess I'm just seeing what I hope to see.

    SPDIF Input - 1kHz @ -70dBFS (v1)
    [​IMG]

    I promise, this is the last time I'll ask about my firmware. I'm gonna follow @Skyline's sage advice.
     
  2. atomicbob

    atomicbob dScope Yoda

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    These are the features that make me think you have v1.

    noise bursts with a period of approximately 2.27 mS (440 Hz)
    Eitr-Mimby4 - annotated.png

    Large jump with small glitch at approximately 2.27 mS intervals (440 Hz)
    Glitch1 - annotated.png

    Your A/D converter has 10x less resolution in re-digitizing the Modi MB. Combine with the A/D anti-alias filter and the glitch will be harder to see than if using a UCA202.
     
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  3. purr1n

    purr1n Finding his inner redneck

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    Maybe Mimby version 1.5. Running changes.
     
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  4. atomicbob

    atomicbob dScope Yoda

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    That is a possibility, implying @gixxerwimp may have a potentially rare version of firmware.
     
  5. Cspirou

    Cspirou They call me Sparky

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    Software isn't OSX compatible but I'm going to find a solution with my Mac Mini which has audio inputs.

    Or figure out how to record data on my nanoscope.
     
  6. gixxerwimp

    gixxerwimp Professional tricycle rider

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    Appreciate you guys trying to make me feel better ... ;)

    If/when I get access to a cleaner A/D converter I'll revisit this. In the meantime, I'll go back to enjoying my Mimby.
     
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  7. ergopower

    ergopower Acquaintance

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    If you were in the lower 48, I'd USPS mine over to ya, but Taipei is a little spendy. The Behringers must be made in China, no way to find one for cheap on Alibaba or other?
     
  8. gixxerwimp

    gixxerwimp Professional tricycle rider

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    I'm a really cheap basturd. Amazon is only charging $7 to ship it to Taiwan. I may cave and order one (edit: for science).
     
  9. Jerry

    Jerry Almost "Made"

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    @atomicbob Can you pse help me with mine? I followed your instructions and got this. I have no idea how to interpret this. What am I looking for here?

    [​IMG]
     
    Last edited: Jul 30, 2018
  10. purr1n

    purr1n Finding his inner redneck

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    That's -90db signal right? Looks like V2, but with some 60Hz hum / harmonics. Pretty normal under many circumstances. Check cables and cross signal cables perpendicular to power cables. Also try relocating wall warts or other gear far away from the Mimby. Sometimes, it can just be other weird stuff too. You are already doing better than Amir.
     
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  11. purr1n

    purr1n Finding his inner redneck

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    Again, rolling changes to gear over time. EC does it, automobile manufacturers do it, and Schiit has already admitted to doing it. I do know that the glitch was particularly high with the early production Mimby units. The could have been initially addressed with circuit changes or optimization. Software fixes with tricky math might have been added later. And then maybe PCB and component changes - that I suspect may have implemented throughout the entire Schiit line. I'm just making examples up though since I honestly don't know what was done and when they were done.

    Moral of the story: don't worry, be happy.
     
  12. Jerry

    Jerry Almost "Made"

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    Many thanks, Marv. I took a few more samples at -90db. I don't understand why they look so different.

    [​IMG]
    [​IMG]
    [​IMG]
     
  13. atomicbob

    atomicbob dScope Yoda

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    Your measurement has 8 Hz wander and AC mains noise making it difficult to call. What A/D converter are you using? You need to re-measure with time base set to 8 mS instead of 25 mS shown above. Though noisy I might venture a qualified guess at v1. But as Marv mentioned, v1 is more than capable of providing a delightful auditory experience. v2 firmware mostly addresses measurebators. Everyone keep in mind we are discussing -90 dBFS performance on a 16 bit multibit DAC.
     
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  14. atomicbob

    atomicbob dScope Yoda

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    Looking at the first graph with 8 mS time base, it would appear your ADC isn't up to the task of making this measurement. Not enough amplitude resolution. Looking at the other graphs, either your ADC or other components in the system present far greater challenges than the Modi MB LSB resolution.
     
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  15. gixxerwimp

    gixxerwimp Professional tricycle rider

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    So I'm blaming @ergopower for making me cave and buy the UCA202. Amazon got it to me in 5 days. This is all totally for science now. As Bob said, I'm sure this is totally beyond what I'd be able to hear (though it'd be interesting for Marv to try a v1/v2 ABx).

    Preliminary data isn't as conclusive as I was hoping for. Still getting a lot of noise. The amplitude of the input signal was really low for some reason on the old WinXP setup I was using, so I switched to a Thinkpad T540P. Had to install the v1.03 drivers for Eitr.

    The -90dB signal is less bursty with noise, but still has a lot of noise at the top of the sine curve. Mimby-90a.jpg

    The -70dB signal is still spikey at the zero crossover.
    Mimby-70a.jpg

    I'll move the laptop to the living room tonight and try to measure the stack in situ, powered by Cthulhu.
     
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  16. gixxerwimp

    gixxerwimp Professional tricycle rider

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    Hooked it up in situ, turned all laptop radios off and unplugged the power adapter. Everything looks the same. Guess either my Mimby is noisy down at that level or the Berengher is.
     

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