Khadas Tone Board technical measurements

Discussion in 'Source Measurements' started by atomicbob, May 17, 2020.

  1. atomicbob

    atomicbob dScope Yoda

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    Khadas Tone Board technical measurements
    (Khadas TB)

    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, Cal Test CT2593-2 balanced probe
    2. Tecnec 75R spdif cable
    3. Balanced XLR cables Belden 1800F with Neutrik 110R AES connectors (not used on Khadas TB)
    4. Single Ended cables Mogami 2964 1 meter with Amphenol RCA 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
    9. Vaunix Lab Brick USB hub
    10. Shielded 14AWG and 16AWG power cables

    Measurements are made in accordance with AES17:2015

    Khadas TB
    Measurements for record commenced after warmup of 2 hours.
    Measurements were performed over a period of several days.

    Index
    Post 1 - measurement setup description, highlights
    Post 2 - spdif input - SE RCA outputs
    Post 3 - USB ASIO input - SE RCA outputs
    Post 4 - Square wave response
    Post 4 - Effect of external grounding on Gain Linearity
    Post 4 - Effect of USB port interface on distortion and noise floor
    Post 5 - Comparison with Matrix XSP
    Post 6 - reserved for additional data and corrections

    Notable highlights:
    Employs es9038q2m IC contrasted with es9038pro used in Matrix XSP
    Decent performance, especially considering price and size, but don't expect a giant killer
    Dynamic Range > 125 dB on USB ASIO input, rather impressive for a microcontroller shield product
    Gain Linearity tight to -110 dBFS then less than ± 1 dB to -130 dBFS on USB ASIO input
    While less than ± 0.1 dB there is an odd ripple in the frequency response

    Measurement setup picture example:
    DSC_0430_small.jpg
     
    Last edited: May 17, 2020
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  2. atomicbob

    atomicbob dScope Yoda

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    spdif input SE output measurements

    Khadas TB Dynamic Range spdif input SE output
    20200506 Khadas dynamic range FFT spdif SE.png

    Dynamic range, in simplified terms
    1. find maximum output voltage at 0 dBFS
    2. find residual noise with a -60 dBFS 1 KHz stimulus, removed from analysis by window notch
    3. Dynamic Range is the difference between maximum output and residual noise
    Specifics are in AES17 section 9.3 (measurebators do your homework please)
    Example here:
    https://www.maximintegrated.com/en/design/blog/spec-dynamic-range.html

    Why we have a -60 dBFS stimulus (included for certain measurement wankers that don't bother reading AES17 standards)
    Some clever codec designers include an output gate that shuts off when there is no signal present. This has the dual benefit of lowering output idle noise while also gaming the measurements. AES became wise requiring a -60 dBFS stimulus so any such gates are open during measurement and true Dynamic Range performance measured.

    Khadas TB A04 THD+N THD nth-HD FFT spdif input SE output
    20200506 Khadas A04 THD+N THD nth-HD 4+HD+N 60Hz FFT SE 0dBFS - spdif SE.png

    Khadas TB Frequency Response y-axis highly zoomed FFT spdif input SE output
    20200507 Khadas frequency response zoom FFT spdif SE.png

    Khadas TB 50 + 7000 Hz spdif input SE output - Left Channel
    FFT_2_L1T13_1_A.png

    Khadas TB Gain Linearity spdif input SE output - Left Channel
    G2_L1T3_1_A.png

    Khadas TB THD+N vs Frequency spdif input SE output - Left Channel
    G2_L1T5_1_A.png

    Khadas TB Residual Noise SE spdif input SE output - Left Channel
    FFT_2_L1T16_1_A.png

    Complete spdif input SE output analysis report pdf attached
     

    Attached Files:

    Last edited: May 17, 2020
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  3. atomicbob

    atomicbob dScope Yoda

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    USB ASIO input SE output measurements

    Khadas TB Dynamic Range USB ASIO input SE output
    20200506 Khadas dynamic range FFT ASIO SE.png

    Khadas TB A04 THD+N THD nth-HD FFT USB ASIO input SE output
    20200506 Khadas A04 THD+N THD nth-HD 4+HD+N 60Hz FFT SE 0dBFS - ASIO SE.png

    Khadas TB Frequency Response y-axis highly zoomed FFT USB ASIO input SE output
    20200507 Khadas frequency response zoom FFT ASIO SE.png

    Khadas TB 50 + 7000 Hz USB ASIO input SE output - Left Channel
    FFT_2_L1T13_1_A.png

    Khadas TB Gain Linearity USB ASIO input SE output - Left Channel
    G2_L1T3_1_A.png

    Khadas TB THD+N vs Frequency USB ASIO input SE output - Left Channel
    G2_L1T5_1_A.png

    Khadas TB Residual Noise USB ASIO input SE output - Left Channel
    FFT_2_L1T16_1_A.png

    Complete USB input SE output analysis report pdf attached
     

    Attached Files:

    Last edited: May 17, 2020
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  4. atomicbob

    atomicbob dScope Yoda

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    Square wave response

    Measurement conditions
    1. 20Hz square wave except as noted
    2. 44.1 KHz sample rate
    3. USB ASIO input
    4. SE output to oscilloscope

    DAC anti-alias filter ringing can clip on fast transition signals. Leading edges of percussive sounds often have transitions that are nearly that of a square wave which will stimulate filter ringing. All OS DACs have this trait. Most DAC manufacturers gain stage the DAC such that a 0 dBFS sine is just below the power supply limits and thus doesn't clip. When the filter rings, clipping occurs. Using digital attenuation can avoid this unwanted signal modification. How much attenuation is dependent on the filter design. Here is an example for Khadas TB.

    Khadas TB 10mS/div 0 dBFS sine
    20200506-04 Khadas 20 Hz sin 0 dBFS 6 Vpp 10mS div SE - USB.png

    Khadas TB 100uS/div 0 dBFS
    20200506-02 Khadas 20 Hz sqr 0 dBFS 6 Vpp 100uS div SE - USB.png

    Khadas TB 100uS/div -3 dBFS
    20200506-06 Khadas 20 Hz sqr -3 dBFS 4 Vpp 100uS div SE - USB.png

    Effect of external grounding on Gain Linearity

    Khadas TB Gain Linearity spdif ASIO input SE output - Left Channel
    No external ground - floating system
    G2_L1T3_1_A_float.png

    Khadas TB Gain Linearity spdif ASIO input SE output - Left Channel
    External ground - grounded system
    G2_L1T3_1_A_gnd.png


    Effect of USB port interface on distortion and noise floor

    Khadas TB 1000Hz THD+N FFT spdif input SE output
    Dell Latitude D7470 USB 2 port
    FFT_2_L1T12_1_A_Dell_USB.png

    Khadas TB 1000Hz THD+N FFT spdif input SE output
    Vaunix Lab Brick Isolated USB 2 port
    FFT_2_L1T12_1_A_ISO_USB.png
     
    Last edited: May 17, 2020
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  5. atomicbob

    atomicbob dScope Yoda

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    Comparison with Matrix XSP

    Khadas TB Frequency Response y-axis highly zoomed spdif input SE output
    20200507 Khadas frequency response zoom FFT spdif SE.png

    Matrix XSP Frequency Response y-axis highly zoomed AES input SE output
    20200507 Matrix XSP frequency response zoom FFT AES SE.png

    Khadas TB dynamic range spdif input SE output
    20200506 Khadas dynamic range FFT spdif SE.png

    Matrix XSP dynamic range AES input SE output
    20200507 Matrix XSP dynamic range FFT AES SE.png

    Khadas TB A04 THD+N THD nth-HD FFT spdif input SE output
    20200506 Khadas A04 THD+N THD nth-HD 4+HD+N 60Hz FFT SE 0dBFS - spdif SE.png

    Matrix XSP A04 THD+N THD nth-HD FFT AES input SE output
    20200507 Matrix XSP A04 THD+N THD nth-HD 4+HD+N 60Hz FFT 0dBFS - AES SE.png

    Khadas TB Gain Linearity spdif input SE output - Left Channel
    G2_L1T3_1_A.png

    Matrix XSP Gain Linearity AES input SE output - Left Channel
    G2_L1T3_1_A.png

    Khadas TB Residual Noise spdif input SE output - Left Channel
    FFT_2_L1T16_1_A.png

    Matrix XSP Residual Noise AES input SE output - Left Channel
    FFT_2_L1T16_1_A.png

    Editorial: I wish to point out how consistent methods and reporting allow accurate comparisons to be made, across data from many components measured. Comparisons may be made among any of the technical measurements presented, though it is necessary to watch the X and Y axis, and also note there was a format change, which was a big deal as discussed here:
    dScope measurements proposed post format change RFC
     
    Last edited: May 17, 2020
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  6. atomicbob

    atomicbob dScope Yoda

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    reserved for additional data and corrections
     
  7. Priidik

    Priidik Friend

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    Awesome. That's the kind of stuff not so easy to come across.
     
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  8. Serious

    Serious Inquisitive Frequency Response Plot

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    Something like that is very common in consumer electronics, isn't it? Phone speaker hiss is audible to me when playing a very quiet signal (or even digital silence) at up to 25cm distance or so, but thankfully it mutes itself when no output is present.
     
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