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Thread: 9 pin socket base with metal centre

  1. #1
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    9 pin socket base with metal centre

    I've just noticed that the 9 pin base I've received has a metal centre with a tab on it and as I'm going to be using a 12ax7 tube that has no pin in the centre should I leave the centre tab unconnected or does it need to be connected to something or do i need to order a socket without the shield ??

  2. #2
    Lifetime Member Enzo's Avatar
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    Ignore it, or use it as a tie point for components.

    The center terminal used to be a lot more common than it is today. I might guess because in RF circuits like TV sets and radios, keeping component leads short mattered more than in guitar amps.
    Education is what you're left with after you have forgotten what you have learned.

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    Thanks enzo

  4. #4
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    Connect it to 0V and use it as the local star ground point. Thats what I do with these type of sockets.
    Cheers,
    Ian

  5. #5
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    Good idea thanks
    Scott

  6. #6
    Old Timer
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    On EL84 amps I fit the grid stopper between the centre pin and grid pin as the 'unused' pins on an EL84 are all internal connections.
    g1 likes this.

  7. #7
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    They can make it awkward to wire heaters in accordance with Merlin’s guidance. Cutting the terminal off leaves sharp edges that might damage the insulation of wire passing over it (probably not a big deal).
    With ceramic sockets the post is part of a crimped fastener that holds the socket assembly together, so it can’t be removed, in the way that the centre posts of plastic sockets can. Don’t ask me how I discovered this.
    Last edited by pdf64; 02-11-2018 at 02:33 PM.
    Justin Thomas likes this.

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