BottleHead Crack technical measurements

Discussion in 'Headphone Amplifier Measurements' started by atomicbob, Nov 29, 2017.

  1. atomicbob

    atomicbob Friend

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    Bottlehead Crack 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
    2. 300 ohm load used for measurements
    3. Unbalanced cables Worlds Best Cable Gotham GAC-2 RCA
    4. Vaunix Lab Brick USB hub for measurement equipment
    5. 0 dB gain @ 0.775 Vrms 0 dBu except as noted, typically -16 dBu (0.122 Vrms)
    6. Bottlehead Crack gain knob at approximately 10:30 to achieve 0 dB gain
    7. Nearly stock Crack:
    a. no Speedball
    b. film bypass caps added to output electrolytic capacitors
    c. rebiased for e80cc instead of 12au7

    Reference:

    0.775 Vrms @ 30 ohms is 20 mW producing approximately 101 dB SPL in HE-500 with sensitivity of 89 dB/mW
    0.775 Vrms @ 300 ohms is 2 mW producing approximately 101 dB SPL in HD650 with sensitivity of 98 dB/mW
    0.122 Vrms @ 300 ohms is 50 uW producing approximately 84 dB SPL in HD800 with sensitivity of 97 dB/mW


    Highlights:

    The BH Crack is a simple audio path and provides a great auditory experience with HD6x0 and HD800 headphones.
    THD and THD+N is consistent across the spectrum and is 2nd harmonic dominant. 3rd harmonic is 40 dB lower than 2nd.
    I still enjoy numerous evenings listening to this amp. Tube rolling enables many addictive sonic signatures.


    Picture of the Audio Lab setup for Bottlehead Crack / Liquid Crimson measurements
    DSC_0005a.jpg

    300 ohm load part 1 of 3

    Bottlehead Crack square wave 20 Hz 2 Vpp 10 mS / div 300R load
    20171128 SigGen Crack 20 Hz square 2000mVpp 10mS div 100KHz filter 300R.png

    Bottlehead Crack square wave 20 Hz 2 Vpp 10 uS / div 300R load
    20171128 SigGen Crack 20 Hz square 2000mVpp 10uS div 100KHz filter 300R.png

    Bottlehead Crack square wave 20 Hz 2 Vpp 2 uS / div 300R load
    20171128 SigGen Crack 20 Hz square 2000mVpp 2uS div 5MHz filter 300R.png

    Bottlehead Crack amplitude - phase - gain (A01) 300R load
    20171128 Crack A01 amplitude - phase - gain 300R.png

    Bottlehead Crack signal to noise (A07) 300R load
    20171128 Crack A07 SNR 300R.png

    Bottlehead Crack THD+N THD nth harmonic distortion (A04) 300R load
    20171128 Crack A04 THD+N  THD  nth-HD 300R.png

    Bottlehead Crack THD+N THD nth harmonic distortion (A04) with FFT 300R load
    20171128 Crack A04 THD+N  THD  nth-HD FFT 300R.png

    Bottlehead Crack Crosstalk (A08 A09) 300R load
    20171128 Crack A08 A09 Crosstalk 300R.png


     
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  2. atomicbob

    atomicbob Friend

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    300 ohm load part 2 of 3

    editorial - I believe there is a tendency to focus too much 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.

    Here are graphs for the various measurements

    Bottlehead Crack Frequency Response and Interchannel Phase pg 1/2 300R load
    G2_L1T2_1_A.png

    Bottlehead Crack Frequency Response and Interchannel Phase pg 2/2 300R load
    G2_L1T2_1_B.png

    Bottlehead Crack Gain vs Amplitude Left 300R load
    G2_L1T3_1_A.png

    Bottlehead Crack Gain vs Amplitude Right 300R load
    G2_L1T3_1_B.png

    Bottlehead Crack THD+N vs Frequency Left 300R load
    G2_L1T5_1_A.png

    Bottlehead Crack THD+N vs Frequency Right 300R load
    G2_L1T5_1_B.png

    Bottlehead Crack THD+N vs Amplitude Left 300R load
    G2_L1T6_1_A.png

    Bottlehead Crack THD+N vs Amplitude Right 300R load
    G2_L1T6_1_B.png

    Bottlehead Crack Crosstalk Left to Right vs Frequency 300R load
    G1_L1T10_1.png

    Bottlehead Crack Crosstalk Right to Left vs Frequency 300R load
    G0_L1T11_1.png

     
    Last edited: Nov 29, 2017
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  3. atomicbob

    atomicbob Friend

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    300 ohm load part 3 of 3

    Bottlehead Crack THD THD+N vs Frequency with 1 KHz spectrum Left and Right 300R load
    20171128 Crack THD THD+N vs Freq 300R.png

    Bottlehead Crack 1 KHz spectrum Left and Right 300R load
    20171128 Crack 1 KHz THD+N THD FFT 0dBu 300R.png

    Bottlehead Crack 50 Hz + 7000 Hz spectrum Left and Right 300R load
    20171128 Crack 50+7000Hz 0dBu 300R.png

    Bottlehead Crack 600 Hz + 1700 Hz spectrum Left and Right 300R load
    20171128 Crack 600+1700Hz 0dBu 300R.png

    Bottlehead Crack IMD spectrum Left and Right 300R load
    20171128 Crack 19+20KHz -16dBu 300R.png

    Bottlehead Crack residual noise spectrum Left and Right 300R load
    20171128 Crack residual noise A=0dB 300R.png

     
    Last edited: Nov 29, 2017
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  4. atomicbob

    atomicbob Friend

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    reserved 4/4.
     
  5. Cspirou

    Cspirou Friend

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    Great job as usual! I believe this is the first time I've seen an all tube amp measurement from you and glad to see the Crack even though OJ posted his own measurements before.
     
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