Shortest Way 51+ multi-tube technical measurements

Discussion in 'Headphone Amplifier Measurements' started by atomicbob, Dec 2, 2020.

  1. atomicbob

    atomicbob dScope Yoda

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    Shortest Way 51+ (sw51+) multi-tube 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, Keysight 34465A, Cal Test CT2593-2 balanced probe (if used)
    2. Balanced XLR cables Belden 1800F with Neutrik 110R AES connectors (if used)
    3. Single Ended cables Audioblast HQ-1 1.5 ft with Rean RCA connectors
    4. 300 ohm loads used for measurements
    5. dScope analyzer sample rate 48 KHz unless otherwise noted
    6. 0dBu level used for testing unless otherwise noted
    7. Amplifier input to output gain set to achieve 0 dB unless otherwise noted
    8. Audioquest Forest and Schiit Pyst USB cables used with measurement equipment
    9. Vaunix Lab Brick USB hub
    10. Shielded 14AWG and 16AWG power cables

    Measurements made in accordance with AES17:2015

    Sensitivity data for two headphones to keep in mind while viewing these measurements:
    HD 650 impedance 300R, sensitivity 98 dB/mW
    HE-500 impedance 38R, sensitivity 89 dB/mW

    SPL levels for above headphones for reference:
    0 dBu 300R 2.00 mW - 101 dBSPL @ 98dB/mW
    0 dBu 30R 20.00 mW - 102 dBSPL @ 89dB/mW

    All testing performed at 0 dBu unless otherwise noted.
    This level is consistent with listening to headphones (referenced above) at 90 dBSPL average with peaks to 100 dBSPL, if the music has 10 dB Peak to Avg ratio. That is LOUD for long listening sessions.

    Shortest Way 51+ (sw51+) multi-tube measurements
    Measurements commenced for each tube pair after 1 hour of warmup.
    Measurements were performed over a period of several weeks.
    As this is a complex measurement task it was limited to 300R load.

    Index
    Post 1 - measurement setup description, highlights
    Post 2 - pictures of the tubes tested
    Post 3 - distortion FFT at 1 KHz
    Post 4 - square wave response
    Post 5 - frequency response
    Post 6 - residual noise
    Post 7 - THD+N and 4+HD+N vs amplitude
    Post 8 - Linearity and 4+HD+N vs amplitude at 440 Hz
    Post 9 - Linearity and 4+HD+N vs amplitude at 40 Hz
    Post 10 - multitone response
    Post 11 - pdf reports
    Post 12 - reserved for corrections or additional data

    Measurement Setup picture:
    SW51+_multi-tube_small.jpg

    Listening evaluation picture
    Towering_Delight.jpg

    Notable highlights:
    I developed a custom suite of measurements for this unusual comparison of amplifier performance across a number of tubes from various manufacturers.
    The standard suite of measurements with 6Z51P can be found here .
    Select Left channel graphs will be presented in posts 3 through 10.
    Full pdf reports are found in post 11 and contain much more data.

    As expected all tubes measured similar to one another, though differences are evident.
    It would be a fair question to ask if the differences between multiple tubes from the same manufacturer would vary similarly to this data from across the manufacturers. That may be a future exploration.

    One tube had a measurably higher noise floor as will be seen in the Distortion 1 KHz below. The right channel counterpart was more in line with all others. That tube did make some audible noise during warmup but once at operating temperature no further noise was noticed.

    Typical operating temperature across all tubes was:
    Left channel: 220 °F / 104 °C
    Right channel: 205 °F / 96 °C

    Output Impedance R by tube:
    20201213 SW51+ multiple tubes output impedance.png

    Bandwidth in KHz by tube:
    20201213 SW51+ multiple tubes BW.png

    Dynamic Range in dB by tube:
    20201213 SW51+ multiple tubes dynamic range.png

    All data presented will be in the following order:
    Russian 6Z51P (stock tube)
    Amperex Holland 6EJ7
    CGE 6EJ7
    Mullard EF184
    Telefunken EF184
    Tungsram EF184
    Westinghouse 6EJ7
     
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    Last edited: Dec 13, 2020
  2. atomicbob

    atomicbob dScope Yoda

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    Last edited: Dec 3, 2020
  3. atomicbob

    atomicbob dScope Yoda

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    Distortion FFT at 1 KHz

    Russian 6Z51P (stock tube)
    FFT_2_L1T2_1_A_6Z51P.png

    Amperex Holland 6EJ7
    FFT_2_L1T2_1_A_AH6EJ7.png

    CGE 6EJ7
    FFT_2_L1T2_1_A_CGE6EJ7.png

    Mullard EF184
    FFT_2_L1T2_1_A_MEF184.png

    Telefunken EF184
    FFT_2_L1T2_1_A_TFEF184.png

    Tungsram EF184
    FFT_2_L1T2_1_A_TREF184 - annotated.png
    Left channel Tungsram exhibited more residual noise than others. Compare with Right channel Tungsram (graph below) which behaves similar to the other tubes. Probably just an anomalous tube.
    FFT_2_L1T2_1_B_TREF184.png

    Westinghouse 6EJ7
    FFT_2_L1T2_1_A_W6EJ7.png
     
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    Last edited: Dec 13, 2020
  4. atomicbob

    atomicbob dScope Yoda

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    Square wave response

    Russian 6Z51P (stock tube)
    01 20201030 SigGen SW51+ 6Z51P 20 Hz square 2000mVpp 20uS div 5MHz filter 300R HiZ - BW calc.png

    Amperex Holland 6EJ7
    02 20201030 SigGen SW51+ AH6EJ7 20 Hz square 2000mVpp 20uS div 5MHz filter 300R HiZ - BW calc.png

    CGE 6EJ7
    02 20201030 SigGen SW51+ CGE6EJ7 20 Hz square 2000mVpp 20uS div 5MHz filter 300R HiZ - BW calc.png

    Mullard EF184
    03 20201031 SigGen SW51+ MEF184 20 Hz square 2000mVpp 20uS div 5MHz filter 300R HiZ - BW calc.png

    Telefunken EF184
    04 20201129 SigGen SW51+ TFEF184 20 Hz square 2000mVpp 20uS div 5MHz filter 300R HiZ - BW calc.png

    Tungsram EF184
    05 20201129 SigGen SW51+ TREF184 20 Hz square 2000mVpp 20uS div 5MHz filter 300R HiZ - BW calc.png

    Westinghouse 6EJ7
    06 20201031 SigGen SW51+ W6EJ7 20 Hz square 2000mVpp 20uS div 5MHz filter 300R HiZ - BW calc.png
     
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    Last edited: Dec 13, 2020
  5. atomicbob

    atomicbob dScope Yoda

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    Frequency response

    Russian 6Z51P (stock tube)
    G2_L1T1_1_6Z51P.png

    Amperex Holland 6EJ7
    G2_L1T1_1_AH6EJ7.png

    CGE 6EJ7
    G2_L1T1_1_CGE6EJ7.png

    Mullard EF184
    G2_L1T1_1_MEF184.png

    Telefunken EF184
    G2_L1T1_1_TFEF184.png

    Tungsram EF184
    G2_L1T1_1_TREF184.png

    Westinghouse 6EJ7
    G2_L1T1_1_W6EJ7.png
     
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    Last edited: Dec 13, 2020
  6. atomicbob

    atomicbob dScope Yoda

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    Residual noise

    Russian 6Z51P (stock tube)
    FFT_2_L1T4_1_A_6Z51P.png

    Amperex Holland 6EJ7
    FFT_2_L1T4_1_A_AH6EJ7.png

    CGE 6EJ7
    FFT_2_L1T4_1_A_CGE6EJ7.png

    Mullard EF184
    FFT_2_L1T4_1_A_MEF184.png

    Telefunken EF184
    FFT_2_L1T4_1_A_TFEF184.png

    Tungsram EF184
    FFT_2_L1T4_1_A_TREF184.png

    Westinghouse 6EJ7
    FFT_2_L1T4_1_A_W6EJ7.png
     
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    Last edited: Dec 13, 2020
  7. atomicbob

    atomicbob dScope Yoda

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    THD+N and 4+HD+N vs amplitude

    Russian 6Z51P (stock tube)
    G2_L1T5_1_6Z51P.png

    Amperex Holland 6EJ7
    G2_L1T5_1_AH6EJ7.png

    CGE 6EJ7
    G2_L1T5_1_CGE6EJ7.png

    Mullard EF184
    G2_L1T5_1_MEF184.png

    Telefunken EF184
    G2_L1T5_1_TFEF184.png

    Tungsram EF184
    G2_L1T5_1_TREF184.png

    Westinghouse 6EJ7
    G2_L1T5_1_W6EJ7.png
     
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    Last edited: Dec 13, 2020
  8. atomicbob

    atomicbob dScope Yoda

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    Linearity and 4+HD+N vs amplitude at 440 Hz

    Russian 6Z51P (stock tube)
    G2_L1T6_1_6Z51P.png

    Amperex Holland 6EJ7
    G2_L1T6_1_AH6EJ7.png

    CGE 6EJ7
    G2_L1T6_1_CGE6EJ7.png

    Mullard EF184
    G2_L1T6_1_MEF184.png

    Telefunken EF184
    G2_L1T6_1_TFEF184.png

    Tungsram EF184
    G2_L1T6_1_TREF184.png

    Westinghouse 6EJ7
    G2_L1T6_1_W6EJ7.png
     
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    Last edited: Dec 13, 2020
  9. atomicbob

    atomicbob dScope Yoda

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    Linearity and 4+HD+N vs amplitude at 40 Hz

    Russian 6Z51P (stock tube)
    G2_L1T7_1_6Z51P.png

    Amperex Holland 6EJ7
    G2_L1T7_1_AH6EJ7.png

    CGE 6EJ7
    G2_L1T7_1_CGE6EJ7.png

    Mullard EF184
    G2_L1T7_1_MEF184.png

    Telefunken EF184
    G2_L1T7_1_TFEF184.png

    Tungsram EF184
    G2_L1T7_1_TREF184.png

    Westinghouse 6EJ7
    G2_L1T7_1_W6EJ7.png
     
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    Last edited: Dec 13, 2020
  10. atomicbob

    atomicbob dScope Yoda

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    Multitone response

    Russian 6Z51P (stock tube)
    FFT_2_L1T8_1_A_6Z51P.png

    Amperex Holland 6EJ7
    FFT_2_L1T8_1_A_AH6EJ7.png

    CGE 6EJ7
    FFT_2_L1T8_1_A_CGE6EJ7.png

    Mullard EF184
    FFT_2_L1T8_1_A_MEF184.png

    Telefunken EF184
    FFT_2_L1T8_1_A_TFEF184.png

    Tungsram EF184
    FFT_2_L1T8_1_A_TREF184.png

    Westinghouse 6EJ7
    FFT_2_L1T8_1_A_W6EJ7.png
     
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    Last edited: Dec 13, 2020
  11. atomicbob

    atomicbob dScope Yoda

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    Full pdf reports

    The attached reports contain right channel graphs and more data than presented in the posts above.
     

    Attached Files:

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  12. atomicbob

    atomicbob dScope Yoda

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    Reserved for corrections or additional data.
     
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  13. gixxerwimp

    gixxerwimp Professional tricycle rider

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    Once again, thanks for doing all the heavy lifting, @atomicbob. I'm not really sure what to look for and how to correlate it with how the different tubes sound (or if it's even possible to do so).

    These are my very rough notes for the tubes I sent you (compared to my Mullard RCAs).
    • Matsushita (Westinghouse): too forward/bright
    • CGE: not as forward/bright, but still more than I like, bass somewhat bloated/bloomy
    • Amperex EF184 (Holland): bright and thin (measurements TBD)
     
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  14. atomicbob

    atomicbob dScope Yoda

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    20201213 - Data for Amperex Holland 6EJ7 added.
     
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