Dangerous Music Convert-2 technical measurements

Discussion in 'Source Measurements' started by atomicbob, May 1, 2019.

  1. atomicbob

    atomicbob dScope Yoda

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    Dangerous Music Convert-2 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 balanced (Bal) output XLR
    3. Balanced cables Canare L-4E6S starquad (analog) and Belden 1800F with Neutrik XLR connectors (digital)
    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
    11. SRS FS725 10MHz rubidium time reference
    12. Antelope Audio LiveClock (10MHz to SR wordclock)


    Measurements performed with following Convert-2 parameters (unless otherwise noted):
    1. Reference output set to +18 dBu
    2. Output trim engaged and set for 0 dBFS = 2.8 dBu (1.07Vrms)
    3. Internal clock


    Measurements were acquired over several days.
    Each day measurements commenced after 2 hours of warmup.
    Each day measurements were performed over a period of 8 hours.


    Index
    Post 1 - measurement setup description, highlights
    Post 2 - AES input - Balanced outputs part A
    Post 3 - AES input - Balanced outputs part B
    Post 4 - USB input - Balanced outputs part A
    Post 5 - USB input - Balanced outputs part B
    Post 6 - Internal Trim vs External Stepped Attenuator
    Post 6 - Filter Response vs Sample Rate
    Post 7 - Dante AES - gain linearity and inferred jitter int vs ext clock


    Notable highlights:
    Convert-2 has hot outputs, +22dBu with no trim engaged (9.76 Vrms)
    Word clock input for external synchronization and disciplining
    Distortion and residual noise exceptionally low
    Excellent out-of-band noise rejection (see imaging measurements)
    Slight channel imbalance when internal trim engaged


    Setup picture:
    DSC_0002_F13_small.jpg
     
    Last edited: May 1, 2019
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  2. atomicbob

    atomicbob dScope Yoda

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    AES input balanced output measurements part A

    THD and THD+N spectrum at 1 KHz
    20181227-01 convert2 Bal THD THD+N spectrum - AES.PNG

    THD and THD+N vs frequency
    20181227-02 convert2 Bal THD THD+N vs frequency - AES.PNG

    THD and THD+N vs amplitude at 1 KHz
    20181227-03 convert2 Bal THD THD+N vs amplitude - AES.PNG

    IMD spectrum
    20181227-04 convert2 Bal IMD spectrum - AES.PNG

    IMD vs amplitude
    20181227-05 convert2 Bal IMD vs amplitude - AES.PNG

    Frequency Response
    20181227-06 convert2 Bal FR - AES.PNG

    Frequency Response (y-axis zoom)
    20181227-07 convert2 Bal FR Y axis highly zoomed - AES.PNG

    Inferred Jitter
    20181227-09 convert2 Bal inferred jitter - 7 KHz BW - AES.PNG

    1 KHz gain linearity
    20181227-11 convert2 Bal 1 KHz gain linearity - AES.PNG

    Imaging
    20181227-13 convert2 Bal imaging - AES.PNG
     
    Last edited: May 1, 2019
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  3. atomicbob

    atomicbob dScope Yoda

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    AES input balanced output measurements part B

    Dynamic Range
    20181227-14 convert2 Bal dynamic range - AES.PNG

    Crosstalk
    20181227-15 convert2 Bal crosstalk - AES.PNG

    50 Hz + 7000 Hz dual tone
    20181227-16 convert2 Bal 50+7000Hz dual tone - AES.png

    600 Hz + 1700 Hz dual tone
    20181227-17 convert2 Bal 600+1700Hz dual tone - AES.png

    1kHz @ -90dBFS
    20181227-18 convert2 Bal 1 KHz -90 dBFS - AES.PNG
    Due to trim adjust this -90 dBFS observation is actually over -100 dB relative
    - an impressive performance.

    1kHz @ -70dBFS
    20181227-19 convert2 Bal 1 KHz -70 dBFS - AES.PNG

    20 Hz square wave 0dBFS 4Vpp 10mS/div
    20181227-20 convert2 Bal 20 Hz sqr 0 dBFS 4 Vpp 10mS div - AES 44K.PNG

    20 Hz square wave 0dBFS 4Vpp 500uS/div
    20181227-21 convert2 Bal 20 Hz sqr 0 dBFS 4 Vpp 500uS div - AES 44K.PNG

    20 Hz square wave 0dBFS 4Vpp 100uS/div
    20181227-22 convert2 Bal 20 Hz sqr 0 dBFS 4 Vpp 100uS div - AES 44K.PNG

    Residual noise and interference
    20181227-40 convert2 Bal noise and interference - AES.PNG
     
    Last edited: May 1, 2019
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  4. atomicbob

    atomicbob dScope Yoda

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    USB input balanced output measurements part A

    THD and THD+N spectrum at 1 KHz
    20181227-01 convert2 Bal THD THD+N spectrum - USB.PNG

    THD and THD+N vs frequency
    20181227-02 convert2 Bal THD THD+N vs frequency - USB - t1.PNG

    THD and THD+N vs amplitude at 1 KHz
    20181227-03 convert2 Bal THD THD+N vs amplitude - USB.PNG

    IMD spectrum
    20181227-04 convert2 Bal IMD spectrum - USB.PNG

    IMD vs amplitude
    20181227-05 convert2 Bal IMD vs amplitude - USB.PNG

    Frequency Response
    20181227-06 convert2 Bal FR - USB.PNG

    Frequency Response (y-axis zoom)
    20181227-07 convert2 Bal FR Y axis highly zoomed - USB.PNG

    Inferred Jitter
    20181227-09 convert2 Bal inferred jitter - 7 KHz BW - USB.PNG

    1 KHz gain linearity
    20181227-11 convert2 Bal 1 KHz gain linearity - USB.PNG

    Imaging
    20181227-13 convert2 Bal imaging - USB.PNG
     
    Last edited: May 1, 2019
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  5. atomicbob

    atomicbob dScope Yoda

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    USB input balanced output measurements part B

    Dynamic Range
    20181227-14 convert2 Bal dynamic range - USB +18dBu.PNG

    Crosstalk
    20181227-15 convert2 Bal crosstalk - USB.PNG

    50 Hz + 7000 Hz dual tone
    20181227-16 convert2 Bal 50+7000Hz dual tone - USB.png

    600 Hz + 1700 Hz dual tone
    20181227-17 convert2 Bal 600+1700Hz dual tone - USB.png

    1kHz @ -90dBFS
    20181227-18 convert2 Bal 1 KHz -90 dBFS - USB.PNG
    Due to trim adjust this -90 dBFS observation is actually over -100 dB relative
    - an impressive performance


    1kHz @ -70dBFS
    20181227-19 convert2 Bal 1 KHz -70 dBFS - USB.PNG

    20 Hz square wave 0dBFS 4Vpp 10mS/div
    20181227-20 convert2 Bal 20 Hz sqr 0 dBFS 4 Vpp 10mS div - USB.PNG

    20 Hz square wave 0dBFS 4Vpp 500uS/div
    20181227-21 convert2 Bal 20 Hz sqr 0 dBFS 4 Vpp 500uS div - USB.PNG

    20 Hz square wave 0dBFS 4Vpp 100uS/div
    20181227-22 convert2 Bal 20 Hz sqr 0 dBFS 4 Vpp 100uS div - USB.PNG

    Residual noise and interference
    20181227-35 convert2 residual noise and interference - USB +18dBu.PNG
     
    Last edited: May 1, 2019
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  6. atomicbob

    atomicbob dScope Yoda

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    Internal Trim vs External Stepped Attenuator

    Dynamic Range Convert-2 cal set to -14dBFS internal trim adjusted to 0dBu
    20181227-64a convert2 Bal dynamic range - AES - cal -14dBFS int trim.PNG

    Dynamic Range Convert-2 cal set to -18dBFS internal trim adjusted to 0dBu
    20181227-64b convert2 Bal dynamic range - AES - cal -18dBFS int trim.PNG

    Dynamic Range Convert-2 cal set to -14dBFS external Goldpoint SA2X adjusted to 0dBu
    20181227-64c convert2 Bal dynamic range - AES - cal -14dBFS goldpt trim.PNG

    Dynamic Range Convert-2 cal set to -18dBFS external Goldpoint SA2X adjusted to 0dBu
    20181227-64d convert2 Bal dynamic range - AES - cal -18dBFS goldpt trim.PNG
    Best performance achieved with this last configuration


    Filter Response vs Sample Rate

    20 Hz square wave 0dBFS 4Vpp 100uS/div AES Sample Rate 44 KHz
    20181227-22 convert2 Bal 20 Hz sqr 0 dBFS 4 Vpp 100uS div - AES 44K.PNG

    20 Hz square wave 0dBFS 4Vpp 20uS/div AES Sample Rate 88 KHz
    20181227-25 convert2 Bal 20 Hz sqr 0 dBFS 4 Vpp 20uS div - AES 88K.PNG

    20 Hz square wave 0dBFS 4Vpp 20uS/div AES Sample Rate 176 KHz
    20181227-26 convert2 Bal 20 Hz sqr 0 dBFS 4 Vpp 20uS div - AES 176K.PNG

    20 Hz square wave 0dBFS 4Vpp 20uS/div AES Sample Rate 44 88 176 KHz overlay
    20181227-27 convert2 Bal 20 Hz sqr 0 dBFS 4 Vpp 20uS div - AES 44 88 176K overlay.PNG
    Higher sample rates result in less filter ringing and faster transition time
    88 KHz is a reasonable compromise

     
    Last edited: May 1, 2019
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  7. atomicbob

    atomicbob dScope Yoda

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    Dante data transport to Convert-2 AES input
    Gain linearity and inferred jitter - internal vs external clock

    1 KHz gain linearity Convert-2 internal clock
    20181227-51 convert2 Bal 1 KHz gain linearity - AES - Dante VSC - 88K int clk.PNG

    1 KHz gain linearity Convert-2 externally clocked by rubidium time reference and LiveClock
    20181227-51 convert2 Bal 1 KHz gain linearity - AES - Dante VSC - 88K ext clk t2.PNG
    Slightly better gain linearity with external disciplining from rubidium time reference + LiveClock combination

    Inferred Jitter Convert-2 internal clock
    20181227-59 convert2 Bal inferred jitter - 7 KHz BW - AES - Dante VSC - 11 KHz - int clk.PNG

    Inferred Jitter Convert-2 externally clocked by rubidium time reference and LiveClock
    20181227-59 convert2 Bal inferred jitter - 7 KHz BW - AES - Dante VSC - 11 KHz - ext clk t2.PNG
    Jitter reduced with external disciplining from rubidium time reference + LiveClock combination
     
    Last edited: May 1, 2019
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