EC Designs MOS24 technical measurements

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  1. atomicbob

    atomicbob dScope Yoda

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    EC Designs MOS24 technical measurements

    Standard Prologue
    If you are unfamiliar with audio measurements please use a search engine with the query:
    "audio measurements" or "audio measurement handbook"
    Look for publications by Richard C. Cabot and also by Bob Metzler, both from Audio Precision. There are other useful publications as well. These will provide basic knowledge.
    Interpretation of the following measurements is beyond the scope of technical measurements posts.


    The data presented were collected as follows:

    1. PrismSound dScope III, picoscope 5243B
    2. DAC SE RCA output
    3. Lifatec toslink cable
    4. Single Ended cables Audioblast HQ-1 1.5 ft with Rean RCA connectors or RG6 with BNC connectors
    5. 100 Kohm load used for measurements
    6. dScope analyzer sample rate 48 KHz unless otherwise noted
    7. DAC 44.1 KHz sample rate, 24 bit depth unless otherwise noted
    9. Audioquest Forest and Schiit Pyst USB cables used for measurement equipment
    9. Vaunix Lab Brick USB hub
    10. Shielded 14AWG and 16AWG power cables


    Measurements commenced after 1 hour of warmup.
    Measurements were performed over a period of 5 hours.

    Index
    Post 1 - measurement setup description, highlights
    Post 2 - optical input - SE RCA outputs part A
    Post 3 - optical input - SE RCA outputs part B
    Post 4 - optical input - SE RCA outputs part C


    Notable highlights:
    MOS24 is battery operated, optically driven with only one point of galvanic connection at the RCA jacks
    This DAC is a case of "The big print giveth but the fine print taketh away"
    NOS operation has near perfect square wave and pulse response; bandwidth greater than 2.5 MHz!!
    But
    Spectrums demonstrate the result of minimal or no anti-alias filter, particularly the Imaging measurement, true of any NOS DAC with minimal or no anti-alias filter, not just the MOS24.

    Great benefit realized by upsampling source material, such as 44 to 88 KHz before sending to DAC
    as with JRiver using SOX sample rate converter.


    Setup picture:
    DSC_0152_small.jpg
     
    Last edited: May 4, 2019
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  2. atomicbob

    atomicbob dScope Yoda

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    Optical input SE output measurements part A

    THD and THD+N spectrum at 1 KHz
    20190429-01 MOS24 SE THD THD+N spectrum - Opt 44K.PNG

    THD and THD+N vs frequency
    20190429-02 MOS24 SE THD THD+N vs frequency - Opt 44K.PNG

    THD and THD+N vs amplitude at 1 KHz
    20190429-03 MOS24 SE THD THD+N vs amplitude - Opt 44K.PNG

    IMD spectrum
    20190429-04 MOS24 SE IMD spectrum - Opt 44K.PNG

    IMD vs amplitude
    20190429-05 MOS24 SE IMD vs amplitude - Opt 44K.PNG

    Frequency Response
    20190429-06 MOS24 SE FR - Opt 44K.PNG

    Frequency Response (y-axis zoom)
    20190429-07 MOS24 SE FR Y axis highly zoomed - Opt 44K.PNG

    Inferred Jitter
    20190429-09 MOS24 SE inferred jitter - 7 KHz BW - Opt 44K.PNG

    1 KHz gain linearity
    20190429-11 MOS24 SE 1 KHz gain linearity - Opt 44K.PNG
     
    Last edited: May 4, 2019
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  3. atomicbob

    atomicbob dScope Yoda

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    Optical input SE output measurements part B

    Imaging 44 KHz Sample Rate
    20190429-13 MOS24 SE imaging - Opt 44K.PNG
    Not wonderful but can be somewhat mitigated by upsampling.

    Imaging 88 KHz Sample Rate
    20190429-13 MOS24 SE imaging - Opt 88K.PNG
    Better imaging response than 44 KHz.

    Dynamic Range
    20190429-14 MOS24 SE dynamic range - Opt 44K.PNG

    Crosstalk
    20190429-15 MOS24 SE crosstalk - Opt 44K.PNG

    50 Hz + 7000 Hz dual tone
    20190429-16 MOS24 SE 50+7000Hz dual tone - Opt 44K.png

    600 Hz + 1700 Hz dual tone
    20190429-17 MOS24 SE 600+1700Hz dual tone - Opt 44K.png

    1kHz @ -90dBFS - 24 bit
    20190429-18 MOS24 SE 1 KHz -90 dBFS - Opt 44K.PNG

    1kHz @ -90dBFS - 16 bit
    20190429-18 MOS24 SE 1 KHz -90 dBFS - 16 bit  - Opt 44K.PNG

    1kHz @ -70dBFS - 24 bit
    20190429-19 MOS24 SE 1 KHz -70 dBFS - Opt 44K.PNG

    Residual noise and interference
    20190429-40 MOS24 SE noise and interference - Opt 44K.PNG
     
    Last edited: May 4, 2019
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  4. atomicbob

    atomicbob dScope Yoda

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    Optical input SE output measurements part C

    Here is the appeal for NOS, nearly perfect square wave response.


    20 Hz square wave 0dBFS 4Vpp 10mS/div
    20190429-20 MOS24 SE 20 Hz sqr 0 dBFS 4 Vpp 10mS div - 1 MHz - Opt 44K.PNG

    20 Hz square wave 0dBFS 4Vpp 100uS/div
    20190429-22 MOS24 SE 20 Hz sqr 0 dBFS 4 Vpp 100uS div - Opt 44K - BW calc.PNG
    Bandwidth estimation: BW (MHz) = 0.35 / RT (mS)
    Where RT = 10 to 90% Rise Time
    0.35 / 138.7 nS = 2.52 MHz

    50 Hz pulse -3dBFS 1.5Vpp 5mS/div
    20190429-25 MOS24 SE 50 Hz pulse -3 dBFS 1500mVpk 5mS div - Opt 44K.PNG
    This is the impulse response to a single sample at 44 KHz. Nearly perfect, impressive.

     
    Last edited: May 4, 2019
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  5. atomicbob

    atomicbob dScope Yoda

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