Mic cable for grid stoppers questions

Discussion in 'Amp Tech Center' started by screefer, Aug 28, 2020.

  1. screefer

    screefer Tele-Holic Silver Supporter

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    I was given this mic cable as not working.
    As was researching shielded wire wire for an amp build, I read that mic cable can be used to shield the grid stoppers and other applications.

    1. Is this shielded cable?

    2. Will this cable work or should I just buy a 50' spool (smallest amount I can find) of RG174?

    IMG_0933.JPG

    3. Could the stray wire have shorted out the signal?

    Thanks for bearing with my limited knowledge
     
  2. Jon Snell

    Jon Snell Tele-Holic

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    If the cable had been stripped back properly, then that would reduce the chance of short circuits.
    Your grid stopper question ... not any advantage to try and screen the stopper resistor, in fact probably will make matters worse, so no it will not help.
    I could not find a photo of single microphone cable stripped but if the photo had only one core, you can see how it should be done. It is called Twin Screened Lead. Screenshot 2020-08-28 at 22.02.26.png As you can see there is a plastic conductive covering around the inner conductors and there is an insulating material covering the inner conductors.
    If you cut the wires too short or don't clamp the wire at the grip point, that will give the symptom of a short circuit.
     
  3. screefer

    screefer Tele-Holic Silver Supporter

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    I'm confused. This cable appears to have only two wires.

    The tinned wire goes to two pins and then soldered to the jack leg.
    The bare wire goes to another pin. I got continuity between the sleeve and tip of the plug jack and the mic end before I cut the wire.
    How should this be wired?
    IMG_0934.JPG

    IMG_0935.JPG
     
  4. dan40

    dan40 Tele-Afflicted

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    There must be a short between the two conductors if you are reading continuity. It may just be a stray wire touching the other where they connect to the jack. If you cut the wire clean on both ends and separate the two conductors at each end, you should not be reading any continuity hopefully.

    If you want to use it in an amplifier, use the center conductor for your signal connection at the input jack and tube socket and ground the outer conductor at one end or the other.
     
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  5. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    With a one conductor shielded cable, the xlr connection should be conductor to pin 2. The shield should connect to pins 1 & 3. With a 1/4 inch phono TS plug, the conductor to tip and the shield to the sleeve.

    Inside the amplifier dan40 gave good advice.
     
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  6. screefer

    screefer Tele-Holic Silver Supporter

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    Thanks guys!
     
  7. David Barnett

    David Barnett Doctor of Teleocity

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    If so it's very poorly shielded. A braided shield would be preferred, this one's shield appears to be just a wrap.
     
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  8. Jon Snell

    Jon Snell Tele-Holic

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    Screenshot 2020-08-29 at 09.09.40.png Unbalanced cable with plastic conductive material that must be stripped back before the internal insulator.
     
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  9. Jon Snell

    Jon Snell Tele-Holic

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    Screenshot 2020-08-29 at 09.19.16.png This is your cable. Strip it as I showed on my last post. Better still, use better quality unbalanced microphone cable.
     
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  10. screefer

    screefer Tele-Holic Silver Supporter

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