LH Geek Out 450

Discussion in 'Source Measurements' started by Earfonia, Dec 10, 2015.

  1. Earfonia

    Earfonia Rando

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    Recently I checked the Geek Out 450 output on DSO to check the square wave output from the 2 digital filters. I have 2 GO 450, the Black one bought from the early batch, and Silver one from referral program, I guess from later batch of production. Both have been upgraded to the latest firmware (1V5), so what was previously volume control buttons now become selector for digital filter.

    Correct me if I'm wrong, I guess the volume UP button is for TCM (Time Coherence Mode), and volume DOWN button is for FRM (Frequency Response Mode).

    Measurement shows different result on both Geek Outs, also the maximum voltage output is higher on the Black Geek Out.

    All measurement is done on the 0.47 ohm headphone output of Geek Out 450, using Owon VDS3102 DSO and 600 ohms load (resistor).



    Black Geek Out 450 (early batch)

    Volume UP digital filter:
    [​IMG]

    Volume DOWN digital filter:
    [​IMG]

    Maximum voltage output:
    [​IMG]



    Silver Geek Out 450 (later batch)

    Volume UP digital filter:
    [​IMG]
    [​IMG][/IMG]

    Volume DOWN digital filter:
    [​IMG]

    Maximum voltage output:
    [​IMG]



    Black GO 450 firmware and hardware version:
    [​IMG]

    Silver GO 450 firmware and hardware version:
    [​IMG]
     
  2. ultrabike

    ultrabike Measurbator - Admin

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    Dunno, maybe there are some differences in the analog reconstruction filter.

    Try running a 10 Hz square wave and zoom in the transition edges a little.
     
    Last edited: Dec 10, 2015
  3. Earfonia

    Earfonia Rando

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    May I know what's the reason to use low frequency like 10 Hz?
    Isn't it easier to observe the transition edge on oscilloscope using higher frequency? Tx!
     
  4. ultrabike

    ultrabike Measurbator - Admin

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    Something is IMO odd with the DOWN digital filter for the "later batch" Geek Out. The filter oscillations do not seem to have "died out" sufficiently.

    More than high frequency square waves, I was trying to see if you could provide something close to the step response (the running integral of the impulse response). Which is why I was asking for a 10 Hz square wave.

    Is it easier to observe the transition edge on a scope using a higher frequency? I don't see how that maters. You should be able to zoom into the transition band if you want to. I assume the scope you have can lock to 10 Hz. If it's too low, then shoot for 30 or 50 Hz at least. The lower the better.
     
  5. Earfonia

    Earfonia Rando

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    Right, if just zooming on the transition the frequency makes no difference.
    Will try later when I have time, with lower frequency square waves.
     
  6. ultrabike

    ultrabike Measurbator - Admin

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    For your DOWN digital filter screen captures, it might make a difference.

    I also was expecting a more symmetric result on the DOWN digital filter screen captures since I think that filter selection is linear phase. Strange. Maybe I'm missing something. Maybe I'm senile and need more sleep.
     

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