EF86 test results on NOS and production tubes

Discussion in 'Amps and Cabs' started by myles111, Oct 14, 2008.

  1. myles111

    myles111 Member

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    EF86 test results on NOS and production tubes
    Here are some test results on various EF86 tubes. There are mostly NOS tubes here but some production tubes as well. Note that these vary widely from design spec in many cases.

    These were tested using RCA/Mullard design spec which is 250 volts on the plates, 140 on the screen and a 2 volt bias

    Expected results are 3.0mA plate current, 1800 transconductance and a gain of 38 in the test circuit. There are a number of amps made today that push these in their particular circuit to a gain of over 400 and microphonics can be a serious issue in those amps.

    NOS tubes had a much longer service life and rejected physical microphonics much better over life testing than any current production tube.

    Some amps such as the Dr. Z Z-28, Route 66, KT-45 and Delta 88 tolerate poor examples of this tube better than many other amps as the tube is not expected to produce as much gain as in some other amps as a sidenote.

    In the rows below, the first number is plate current output, the second number is transconductance, the third number is not important for this report and the fourth number is true/actual gain in the design spec test circuit. Tube with high gain over spec in the area of 60+ would be very prone to physical microphonics in amps such as a Matchless DC-30.

    These tubes vary widely. If you are in SoCal and have EF86 tubes you wish to have spec'd and curve traced I would be happy to do this for you until I leave SoCal for other places. I am on the road a lot these days so I may be closer to some of you in the future.

    3.0 1800 38 Tesla - spec tube

    3.2 1520 0.005 30.4 Tesla
    4.1 2430 0.0045 54.0 Tesla
    2.7 2030 0.002 101.5 Tesla
    3.4 2160 0.005 43.2 Tesla
    2.6 1950 0.002 97.5 Tesla
    2.7 1920 0.003 64.0 Tesla
    3.0 2060 0.004 38.1 Tesla - Reference tube
    3.0 2140 0.003 71.3 Tesla
    1.9 1710 0.002 85.5 Tesla
    2.8 1990 0.0025 79.6 Tesla
    2.4 1880 0.0025 75.2 Tesla
    4.1 2460 0.004 61.5 Tesla
    2.5 1700 0.002 85.0 Dario
    2.6 1890 0.003 63.0 Tesla
    3.8 1990 0.004 49.8 Tesla
    2.9 1950 0.003 65.0 Tesla
    2.7 1720 0.004 43.0 Dario
    4.0 2130 0.006 35.5 Tesla
    2.7 2030 0.003 67.7 Tesla
    2.5 1640 0.003 54.7 Dario
    2.3 1820 0.003 60.7 Covered / shrink wrapped
    2.4 1840 0.003 61.3 Tesla Covered / shrink wrapped
    2.7 2000 0.003 66.7 Covered / shrink wrapped
    2.3 1680 0.004 42.0 Covered / shrink wrapped
    3.5 2030 0.002 101.5 Dario
    2.7 1600 0.003 53.3 Tesla
    2.9 2050 0.004 51.3 Electro Harmonix
    2.6 1740 0.002 87.0 Tesla
    2.3 1810 0.0025 72.4 Tesla
    3.5 2130 0.003 71.0 Dario
    3.2 2070 0.004 51.8 Tesla
    3.8 2240 0.002 112.0 Dario
    3.2 1930 0.004 48.3 Svetlana winged C
    3.7 2400 0.005 48.0 Tesla
    3.1 1710 0.0045 38.0 Svetlana winged C - Good ref tube
    2.3 1690 0.003 56.3 Svetlana winged C
    2.4 1420 0.004 35.5 Dario
    3.6 1900 0.0045 42.2 Svetlana winged C
    3.1 1820 0.0045 40.4 Svetlana winged C
    3.4 1900 0.003 63.3 Svetlana winged C
    2.4 1650 0.003 55.0 Svetlana winged C
    3.1 1990 0.005 39.8 Tesla
    2.7 1930 0.004 48.3 Tesla
    3.3 1720 0.006 28.7 Tesla
    2.4 1850 0.002 92.5 Tesla
    3.1 2050 0.004 51.3 Tesla

    -end-
     
  2. jtindle

    jtindle Member

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    Thanks for the info, Myles. I've been thinking of getting an NOS EF86 for my Hayseed, but I ain't got a clue what all those numbers mean. How can I use this info when looking to buy an NOS EF86?

    Thanks

    Jeff
     
  3. myles111

    myles111 Member

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    Jeff,

    You really cannot use the individual numbers and what is shown is how widely they vary and this is an indication of a few things ....

    1. Tubes are a crap shoot and if you get a high gain one you can expect more microphonic problems than with a spec tube.

    2. Tubes that are a bit far from spec have a basic problem ... they were not made properly! Bad quality control after bad assembly. Even if the tube has no microphonic issues the bad specs can indicate that the tube may fail prematurely.

    3. Use a trusted vendor with a good warranty policy.

    If you want a fully tested, traced and documented EF86 drop me a note as I know a few vendors that I use that will be able to provide one.
     
  4. sickboy79

    sickboy79 Member

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  5. rockindog

    rockindog Member

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    Myles:

    What..... no tube testing of NOS Mullard mesh screen or solid screen EF-86s? Ah. I have two of the mesh screen Mullards, and one solid screen Mullard, labled "AEL". Real nice tubes. However, I do use the high temp silicon tube dampers just to keep the shakin' down, even in Z heads.
     
  6. myles111

    myles111 Member

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    There were none of those in the batch of stuff I had to test. This was a box of assorted EF86 tubes that I was asked to test.

    Maybe down the road I will get some Mullards. I have a few from KCA but they are in amps and not unused.
     
  7. TRIODEROB

    TRIODEROB Senior Member

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    which EF86 do you think sounds the best in a guitar amp ?
     
  8. myles111

    myles111 Member

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    Depends on the amp, the guitar and your personal taste.

    What is better .... an apple or an orange?
     
  9. Randy Van Sykes

    Randy Van Sykes Member

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    I recently purchased a few JJ EF86 tubes and use them with good dampening rings...they are sounding real good to me so far, just hope they last a while.
     
  10. TRIODEROB

    TRIODEROB Senior Member

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    lets put this another way

    vox AC15

    any recommendations ?
     
  11. midnightlaundry

    midnightlaundry Member

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    Are you running these in V1 with a boost?
     
  12. Randy Van Sykes

    Randy Van Sykes Member

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    There's only one preamp tube slot for the EF86 channel in my Heritage Vox...and yup boosting pretty hard.
    It sounds nice and thick, I don't even use/need the Top Boost channel in the amp.
     
  13. midnightlaundry

    midnightlaundry Member

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    Groovin'. :phones
     
  14. sliberty

    sliberty Member

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    Mine is a DIY AC15-ish circuit, and I have used an NOS Tungsram and a new production EH (cryo treated). Both sound really good. The Tunsgram is currently in my amp though.


     
  15. myles111

    myles111 Member

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    This is really a personal taste issue.
     

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