Eddie Current ZDT Jr. Technical Measurements

Discussion in 'Headphone Amplifier Measurements' started by atomicbob, Dec 17, 2017.

  1. atomicbob

    atomicbob dScope Yoda

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    Eddie Current ZDT Jr. technical measurements

    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 this post.

    The data presented were collected as follows:

    1. PrismSound dScope III, picoscope 5243B, Keysight 34461A DMM
    2. 300 and 30 ohm loads used for measurements
    3. Unbalanced cables Worlds Best Cable Gotham GAC-2 RCA
    4. Vaunix Lab Brick USB hub for measurement equipment
    5. Amplifier gain adjusted to 0 dB gain @ 0.775 Vrms 0 dBu
    6. ZDT Jr gain knob at approximately 1:30 to achieve 0 dB gain High output 300R
    7. GE JAN5654W driver tubes
    8. Stock Russian 6N24P output tubes

    Reference levels :
    +9 dBu 300R 16.00 mW - 110 dBSPL @ 98dB/mW 1% THD ZDT Jr.
    0 dBu 300R 2.00 mW - 101 dBSPL @ 98dB/mW
    -10 dBu 300R 0.20 mW - 91 dBSPL @ 98dB/mW
    -20 dBu 300R 0.02 mW - 81 dBSPL @ 98dB/mW

    +3 dBu 30R 40.00 mW - 105 dBSPL @ 89dB/mW 1% THD ZDT Jr.
    0 dBu 30R 20.00 mW - 102 dBSPL @ 89dB/mW
    -10 dBu 30R 2.00 mW - 92 dBSPL @ 89dB/mW
    -20 dBu 30R 0.20 mW - 82 dBSPL @ 89dB/mW

    Reference data on two headphones:
    HD 650 impedance 300R, sensitivity 98 dB/mW
    HE-500 impedance 38R, sensitivity 89 dB/mW

    Discussion:
    This amplifier has some interesting properties, especially in the distortion measurements. The distortion signature changes with level. Depending on personal preference, headphones and listening sound levels this amplifier will sound markedly different. Pay particular attention to spectrums measured at 0, -10 and -20 dBu. They are presented together for easy comparison.

    My personal preferences include listening typically at an average of 75 dB SPL. Assuming a typical Peak to Average ratio of 10 dB puts peaks at 85 dB SPL. This suggests the measurements at -20 dBu represent my experience with HD6x0 and HD800 headphones. Auditory experiences for someone listening 10 dB SPL average higher are likely to diverge from my experiences.

    The ZDT Jr. has been providing me with enjoyable, non-fatiguing auditory experiences between measurement sets. DAC is an ADI-2 Pro gain structured at -30 dBFS with ref set for +19dBu, and NOS filter. My IVS system is set for 16.5 dBFS headroom which lowers the system to -46 dBFS average with peaks to -36 dBFS. This results in 75 dB SPL average when ZDT Jr. is adjusted for 0 dB gain. When I post the ADI-2 Pro data it will become evident why I have chosen this particular gain structure.

    editorial - I believe there is a tendency to focus excessively on numbers such as THD attempting to reduce a complex topic to a single number representing a sort of goodness rating. Graphs can present far more data conveying a better understanding of the measurement over a range of frequency, levels, etc. Please don't read too much into the numbers presented.


    Picture of the Audio Lab setup for ZDT Jr measurements
    DSC_0003a.jpg


    300 ohm load part 1 of 4

    ZDT Jr THD+N THD nth harmonic distortion (A04) FFT 0dBu 300R load
    20171215 ZDT Jr A04 THD+N  THD  nth-HD FFT 0dBu 300R.png

    ZDT Jr THD+N THD nth harmonic distortion (A04) FFT -10dBu 300R load
    20171215 ZDT Jr A04 THD+N  THD  nth-HD FFT -10dBu 300R.png

    ZDT Jr THD+N THD nth harmonic distortion (A04) FFT -20dBu 300R load
    20171215 ZDT Jr A04 THD+N  THD  nth-HD FFT -20dBu 300R.png

    ZDT Jr THD THD+N vs Freq 0dBu 300R
    20171215 ZDT Jr THD THD+N vs Freq 0dBu 300R.png

    ZDT Jr THD THD+N vs Freq -10dBu 300R
    20171215 ZDT Jr THD THD+N vs Freq -10dBu 300R.png

    ZDT Jr THD THD+N vs Freq -20dBu 300R
    20171215 ZDT Jr THD THD+N vs Freq -20dBu 300R.png

    ZDT Jr 1 KHz spectrum Left and Right +9dBu 300R load
    20171215 ZDT Jr 1 KHz THD+N THD FFT +9dBu 300R.png

    ZDT Jr 1 KHz spectrum Left and Right 0dBu 300R load
    20171215 ZDT Jr 1 KHz THD+N THD FFT 0dBu 300R.png

    ZDT Jr 1 KHz spectrum Left and Right -10dBu 300R load
    20171215 ZDT Jr 1 KHz THD+N THD FFT -10dBu 300R.png

     
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    Last edited: Dec 18, 2017
  2. atomicbob

    atomicbob dScope Yoda

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    300 ohm load part 2 of 4

    ZDT Jr 50 Hz + 7000 Hz spectrum Left and Right 0dBu 300R load
    20171215 ZDT Jr 50+7000Hz 0dBu 300R.png

    ZDT Jr 50 Hz + 7000 Hz spectrum Left and Right -10dBu 300R load
    20171215 ZDT Jr 50+7000Hz -10dBu 300R.png

    ZDT Jr 600 Hz + 1700 Hz spectrum Left and Right 0dBu 300R load
    20171215 ZDT Jr 600+1700Hz 0dBu 300R.png

    ZDT Jr 600 Hz + 1700 Hz spectrum Left and Right -10dBu 300R load
    20171215 ZDT Jr 600+1700Hz -10dBu 300R.png

    ZDT Jr IMD spectrum Left and Right -16dBu 300R load
    20171215 ZDT Jr 19+20KHz -16dBu 300R.png

    ZDT Jr residual noise spectrum Left and Right A=0dB 300R load

    20171215 ZDT Jr residual noise A=0dB 300R.png
     
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    Last edited: Dec 17, 2017
  3. atomicbob

    atomicbob dScope Yoda

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    300 ohm load part 3 of 4

    ZDT Jr square wave 20 Hz 2.9 Vpp 10 mS / div 300R load
    20171215 SigGen ZDT Jr 20 Hz square 2900mVpp 10mS div 100KHz filter 300R.png

    ZDT Jr square wave 20 Hz 2.9 Vpp 10 uS / div 300R load
    20171215 SigGen ZDT Jr 20 Hz square 2900mVpp 10uS div 100KHz filter 300R.png

    ZDT Jr square wave 20 Hz 2.9 Vpp 2 uS / div 300R load
    20171215 SigGen ZDT Jr 20 Hz square 2900mVpp 2uS div 5MHz filter 300R.png

    ZDT Jr amplitude - phase - gain (A01) 300R load
    20171215 ZDT Jr A01 amplitude - phase - gain 300R.png

    ZDT Jr signal to noise (A07) 300R load
    20171215 ZDT Jr A07 SNR 300R.png

    ZDT Jr THD+N THD nth harmonic distortion (A04) 300R load
    20171215 ZDT Jr A04 THD+N  THD  nth-HD 300R.png

    ZDT Jr Crosstalk (A08 A09) 300R load

    20171215 ZDT Jr A08 A09 Crosstalk 300R.png
     
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    Last edited: Dec 17, 2017
  4. atomicbob

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    300 ohm load part 4 of 4

    ZDT Jr Frequency Response and Interchannel Phase pg 1/2 300R load
    G2_L1T2_1_A.png

    ZDT Jr Frequency Response and Interchannel Phase pg 2/2 300R load
    G2_L1T2_1_B.png

    ZDT Jr Gain vs Amplitude Left 300R load

    G2_L1T3_1_A.png

    ZDT Jr Gain vs Amplitude Right 300R load
    G2_L1T3_1_B.png

    ZDT Jr THD+N vs Frequency Left 300R load
    G2_L1T5_1_A.png

    ZDT Jr THD+N vs Frequency Right 300R load
    G2_L1T5_1_B.png

    ZDT Jr THD+N vs Amplitude Left 300R load
    G2_L1T6_1_A.png

    ZDT Jr THD+N vs Amplitude Right 300R load
    G2_L1T6_1_B.png

    ZDT Jr Crosstalk Left to Right vs Frequency 300R load
    G1_L1T10_1.png

    ZDT Jr Crosstalk Right to Left vs Frequency 300R load
    G0_L1T11_1.png

     
    Last edited: Dec 17, 2017
  5. atomicbob

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    30 ohm load part 1 of 4

    ZDT Jr THD+N THD nth harmonic distortion (A04) FFT 0dBu 30R load
    20171216 ZDT Jr A04 THD+N  THD  nth-HD FFT 0dBu 30R.png

    ZDT Jr THD+N THD nth harmonic distortion (A04) FFT -10dBu 30R load
    20171216 ZDT Jr A04 THD+N  THD  nth-HD FFT -10dBu 30R.png

    ZDT Jr THD+N THD nth harmonic distortion (A04) FFT -20dBu 30R load
    20171216 ZDT Jr A04 THD+N  THD  nth-HD FFT -20dBu 30R.png

    ZDT Jr THD THD+N vs Freq 0dBu 30R
    20171216 ZDT Jr THD THD+N vs Freq 0dBu 30R.png

    ZDT Jr THD THD+N vs Freq -10dBu 30R
    20171216 ZDT Jr THD THD+N vs Freq -10dBu 30R.png

    ZDT Jr THD THD+N vs Freq -20dBu 30R
    20171216 ZDT Jr THD THD+N vs Freq -20dBu 30R.png

    ZDT Jr 1 KHz spectrum Left and Right +3dBu 30R load
    20171216 ZDT Jr 1 KHz THD+N THD FFT +3dBu 30R.png

    ZDT Jr 1 KHz spectrum Left and Right 0dBu 30R load
    20171216 ZDT Jr 1 KHz THD+N THD FFT 0dBu 30R.png

    ZDT Jr 1 KHz spectrum Left and Right -10dBu 30R load
    20171216 ZDT Jr 1 KHz THD+N THD FFT -10dBu 30R.png

     
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    Last edited: Dec 17, 2017
  6. atomicbob

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    30 ohm load part 2 of 4

    ZDT Jr 50 Hz + 7000 Hz spectrum Left and Right 0dBu 30R load
    20171216 ZDT Jr 50+7000Hz 0dBu 30R.png

    ZDT Jr 50 Hz + 7000 Hz spectrum Left and Right -10dBu 30R load
    20171216 ZDT Jr 50+7000Hz -10dBu 30R.png

    ZDT Jr 600 Hz + 1700 Hz spectrum Left and Right 0dBu 30R load
    20171216 ZDT Jr 600+1700Hz 0dBu 30R.png

    ZDT Jr 600 Hz + 1700 Hz spectrum Left and Right -10dBu 30R load
    20171216 ZDT Jr 600+1700Hz -10dBu 30R.png

    ZDT Jr IMD spectrum Left and Right -16dBu 30R load
    20171216 ZDT Jr 19+20KHz -16dBu 30R.png

    ZDT Jr residual noise spectrum Left and Right A=0dB 30R load

    20171216 ZDT Jr residual noise A=0dB 30R.png
     
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    Last edited: Dec 17, 2017
  7. atomicbob

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    30 ohm load part 3 of 4

    ZDT Jr square wave 20 Hz 2.98 Vpp 10 mS / div 30R load
    20171216 SigGen ZDT Jr 20 Hz square 2980mVpp 10mS div 100KHz filter 30R.png

    ZDT Jr square wave 20 Hz 2.98 Vpp 10 uS / div 30R load
    20171216 SigGen ZDT Jr 20 Hz square 2980mVpp 10uS div 100KHz filter 30R.png

    ZDT Jr square wave 20 Hz 2.98 Vpp 2 uS / div 30R load
    20171216 SigGen ZDT Jr 20 Hz square 2980mVpp 2uS div 5MHz filter 30R.png

    ZDT Jr amplitude - phase - gain (A01) 30R load
    20171216 ZDT Jr A01 amplitude - phase - gain 30R.png

    ZDT Jr signal to noise (A07) 30R load
    20171216 ZDT Jr A07 SNR 30R.png

    ZDT Jr THD+N THD nth harmonic distortion (A04) 30R load
    20171216 ZDT Jr A04 THD+N  THD  nth-HD 30R.png

    ZDT Jr Crosstalk (A08 A09) 30R load
    20171216 ZDT Jr A08 A09 Crosstalk 30R.png
     
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    Last edited: Dec 17, 2017
  8. atomicbob

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    30 ohm load part 4 of 4

    ZDT Jr Frequency Response and Interchannel Phase pg 1/2 30R load
    G2_L1T2_1_A.png

    ZDT Jr Frequency Response and Interchannel Phase pg 2/2 30R load
    G2_L1T2_1_B.png

    ZDT Jr Gain vs Amplitude Left 30R load
    G2_L1T3_1_A.png

    ZDT Jr Gain vs Amplitude Right 30R load
    G2_L1T3_1_B.png

    ZDT Jr THD+N vs Frequency Left 30R load
    G2_L1T5_1_A.png

    ZDT Jr THD+N vs Frequency Right 30R load
    G2_L1T5_1_B.png

    ZDT Jr THD+N vs Amplitude Left 30R load
    G2_L1T6_1_A.png

    ZDT Jr THD+N vs Amplitude Right 30R load
    G2_L1T6_1_B.png

    ZDT Jr Crosstalk Left to Right vs Frequency 30R load
    G1_L1T10_1.png

    ZDT Jr Crosstalk Right to Left vs Frequency 30R load

    G0_L1T11_1.png
     
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    Last edited: Dec 17, 2017
  9. atomicbob

    atomicbob dScope Yoda

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    Last edited: Dec 18, 2017
  10. atomicbob

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