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Playing with valves

Discussion in 'General Electronics Discussion' started by (*steve*), Jun 18, 2016.

  1. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    I've been playing with some funny evacuated glass tubes. And I've been starving their anodes!

    4GK5-A.png 4GK5-B.png 6AF4A-A.png 6AF4A-B.png 6C4-A.png 6C4-B.png

    These graphs are a bugger to do manually.
     
    davenn likes this.
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    wooden_valve_socket.jpg

    I may not be making valves, but I have to make valve sockets!

    wooden_valve_socket_2.jpg

    And another view. A wooden 12 pin socket.

    When I'm running tests I use a special set of probes I've made.

    valve_under_test.jpg
     
    davenn likes this.
  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    And now I have a pair of valve breadboards. Shown with valves plugged in.

    WP_20160703_13_59_28_Pro.jpg

    WP_20160703_13_59_56_Pro.jpg
     
    CDRIVE likes this.
  4. Bluejets

    Bluejets

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  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    It's far cheaper to make them. And faster. And with as many pins as I need (found any reasonably priced 12 pin valve sockets?)

    We're in an era when the valves cost less than the sockets.
     
  6. Minder

    Minder

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  7. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    No, they're evacuated glass IC's, aka compactrons.
     
  8. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    The Russians are coming!!!!

    WP_20160724_17_08_22_Pro.jpg
     
  9. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Here are some more pretty pictures.

    I'm using a 1J24B the second and third "grids" as the anode, and the anode grounded.

    HT is 12V, and the control grid bias is adjusted so the "anode" voltage is 6.5V. An active load is being used which provides a constant 500uA anode current.

    Enough of the blah blah. Here's some pictures.

    First with a 25mV signal:
    WP_20160731_19_24_49_Pro (2).jpg

    Then with a 100mV signal:
    WP_20160731_17_35_29_Pro.jpg

    3db points are around 500mHz (yes, milliHertz) to 20kHz.
     
    Last edited: Jul 31, 2016
  10. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    And now with a 250mV peak signal (which represents probably the largest reasonable input signal.

    WP_20160731_20_59_06_Pro.jpg
     

    Attached Files:

  11. Sunnysky

    Sunnysky

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    Irfanview makes graph snapshots easy
    Alt+PrtScn to capture the window
    Ctrl+V to paste into irfanview
    Draw a rectangle
    then either Ctrl+Y to crop
    or Ctrl+C to copy
    then Ctrl+V to paste here upload_2016-7-31_10-8-17.png

    With practice it takes me 15 seconds using a pinned shortcut to i_view in the taskbar.
    upload_2016-7-31_10-10-2.png
    Paste only works after<More options> on an edit here.
     
  12. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    And now with a 1v input signal...

    WP_20160731_21_36_27_Pro.jpg

    Note the lower gain.

    Here is the circuit

    WP_20160731_21_37_15_Pro.jpg
     
    davenn likes this.
  13. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    The cut and paste isn't the issue, its the recording of all the raw data and entering it into excel.
     
    davenn likes this.
  14. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Some more measurements last night.

    With a 25mV (RMS) input, the THD is around 0.6% with a SNR of about 65dB.

    The THD remains almost constant to 100mV input. At 175mV the THD rises to 2.5%, 250mV it's 5.5%, and at 500mV it is 11%.

    Measurements were almost constant from 200Hz to 10kHz. Interestingly, THD falls but the noise floor rises (resulting in a lower SNR) at 20kHz and beyond.

    These results are obtained with the valve operating open loop.

    Interestingly, the valve bias point affects THD fairly strongly. It was previously noted that it affects the gain and bandwidth, and I'm unsure if this is an additional effect or a result of the other effects.
     
    Last edited: Sep 26, 2016
    davenn likes this.
  15. davenn

    davenn Moderator

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    interesting results
    I have never played around with tubes in this way before
    my stuff has always been repair/restoration of old gear


    D
     
  16. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    It is certainly a learning experience.

    When I report things like the snr and THD to my musician colleague he encourages me with the explanation that these are expected or even desired.
     
    davenn likes this.
  17. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    Steve, I found my way here via the AudioGuru topic I started. How the hell have I missed this topic? Like you I've never done any design work with tubes but I serviced boat loads of them back in the day. I did build quite a few vacuum tube designs from the ARRL Handbooks but that doesn't qualify as designing.

    You've also been keeping your woodworking skills secret. I love the box joints on your home brew sockets! If you really want to impress me you can claim they're hand cut and chiseled. :) Is that Boxwood you're using or maybe Holly? I ask because of its cream or white color and also because I can't see any grain.

    Chris
     
  18. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Does it count that I "hand cut and chiseled" the program used to create the cutting outlines for a laser cutter?

    The boxes are made from a rare and valuable timber called MDF :)
     
    hevans1944 and Harald Kapp like this.
  19. bushtech

    bushtech

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    lol
     
  20. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    MDF!:eek: Your photos belie that awful truth. Besides using a CNC laser cutter did you also photoshop those pix? :p

    BTW, I've rescinded your master wood worker status because using CNC and Lasers doesn't get you into that fraternity. Though using MDF and actually making that awful stuff look attractive should get you high status in the CNC Laser community! :)

    All joking aside those sockets are both electrically and aesthetically COOL! ;)

    Chris
     
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