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  1. #1

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    Feb 2012
    East Texas

    Default Tube terms and other basics

    I think the term was Microphonic. Someone thumped a piece of tube gear and acted surprised when it made noise.


    Dared SL2000A with the reviewed by H9 Brimar rectifier and Telefunken tubes.

    I am the only person local to play with tubes so a basic understanding of the terms would be a good thing.

    What are the terms? Do tubes just up and echo from time to time?

    (if you read this H9 could you give the explanation of the Tripple Darlington Outputs in the GFA-585? please) Not cheap but an awesome amp

  2. #2

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    Feb 2005
    Plainfield, Illinois


    Real basic, if you make the elements in a valve (tube) vibrate thus changing clearances between them, you can create undesired electron flow making the tube act like a capacitor microphone. This means bumped by people, foot falls or great bass from playing Vamp or Sofi Needs a Ladder.

    Maybe start with wiki and learn about what is in a tube for starters.
    Make yourself necessary to someone. Ralph Waldo Emerson

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  3. #3

    Member Sales Rating: (2)

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    Jun 2004
    New England


    A buffer doesn't have to use vacuum tubes; in analog circuitry, a buffer is an impedance matching device; usually a unity-gain amplifier. There are some really excellent solid state ones. A buffer should be about the most distortionless active stage imaginable; the coloration added by the vacuum tube buffers represents some pretty creative liberty with the design of a buffer :-P

    The explanation of microphonics above is actually excellent :-) There is capacitance between the electrodes in a vacuum tube - actually, that small (on the order of 10s of picofarads) capacitance has important ramifications - one of which being that a simple single-ended vacuum tube gain stage actually has some local negative feedback (due to the tube itself) even if there is no global negative feedback around the stage.

    The term you really want to spend some time with is "Transistor-like sound" - this is what all vacuum tube amplifiers have aspired to since about 1960 ;-)

    My favorite vacuum tube primer to suggest to tyros, FWIW, is "A Taste of Tubes" published some years back by Anthem:

    A very good resource for almost anyone on basic vacuum tube construction and function is any RCA receiving tube manual. Pete Millett's wonderful site has several of them available for downloading.

    Here's a direct link to one - not too early, and not too late in vacuum tube history (these are large downloads, and Pete's servers are none too fast, but they're worth the wait!)

    Some other fine references from Pete's site: (part 1 of three; see Pete's site for the trifecta)
    all the best,

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