Really dumb amp question

Discussion in 'The Workbench' started by jchrisf, Jan 15, 2020.

  1. jchrisf

    jchrisf Well-Known Member

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    I've been studying amps with the intention to eventually mod and build an amp or two. I've been checking out electronic books from the library and reading a lot. I took an electronics class in college about 20 years ago and learned a lot from a great instructor and I am surprised how much I have forgotten since then as a lot of the basic stuff seemed very easy for me to construct and calculate as I remember it.

    Anyway, one thing I have discovered that I never knew before was that electricity actually flows from negative to positive. Now for the really dumb question:

    If we ground our amps to the chassis, why don't we get shocked when we touch the chassis? I would think electricity would be flowing through it.
     
  2. Micky

    Micky Well-Known Member VIP Member

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    Electricity flows thru the path of least resistance.
    It is not flowing where there is no path.
    Chassis ground and one's body are generally at the same potential, so no flow.
     
  3. South Park

    South Park Well-Known Member

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    You are not the ground. All power wants to go to ground. The center tap hooked to the chassis is a better ground.
     
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  4. Matthews Guitars

    Matthews Guitars Well-Known Member

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    Great efforts are made to ensure that the path to ground is the path of least resistance.

    You must also make great efforts to ensure that YOU do not become the path of least resistance to ground!
     
  5. ampmadscientist

    ampmadscientist Well-Known Member

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    "I've been studying amps with the intention to eventually mod and build an amp or two...."

    Yes, you should have your head examined.
     
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  6. myersbw

    myersbw Well-Known Member

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    Actually, you can get shocked touching the chassis with no power connected or capacitor charged. Everyone so far has alluded to it. When you consider that electricity is pressure-directed electron flow. And, the "pressure" is the "difference of potential charges" between two points. When that potential charge is large enough...zap. So...rub those thick soled shoes on carpet with a wool sweater on and nylon pants (disco all over???) and touch a metal door knob...or an amp chassis...bam!...you will feel it.

    The door does not have to be at "earth ground"...usually it isn't when you touch and get the zap.

    What's also interesting is the study of "hole current". One prof I had in college made that his research study. If an electron travels FROM negative TO a positive potential, the theory is it can't move there unless there's a hole to occupy. As they shift, electrons are traveling - to +, whereas the holes are shifting + to -.
     
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  7. jchrisf

    jchrisf Well-Known Member

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    So where does the grounded electricity flow? It just stops with the chassis or goes through the ground in the electrical plug. This stuff blows my mind. What kind of voltage is hitting ground?
     
  8. guzzis3

    guzzis3 Well-Known Member

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    The electricity goes round and round. It only flows if there is a destination. The water analogy isn't technically correct but it helps people get the initial idea.

    If you have a reservoir of water with no outlet the water doesn't go anywhere. Electrons don't have to flow between atoms. They can sit still perfectly happy in their home atom.

    If you pump water it will flow. You are applying pressure and it flows most readily toward low resistance options. If you have a 1/4" pipe and a 3" pipe where will most of the water flow ? Electrons skip from atom to atom. Some atoms are easier to skip across than others. This is where most of the electrons will go. Copper steel etc, rather than timber or (most) plastics. With enough pressure the electrons will push across less conductive materials like plastic and even air.

    The electrons never just go some place new set up home and stay. You need a circuit so they can return to the origion eventually. They don't all have to return, which is why you can build up a negative or positive static charge. Given a chance though this will flow and stabilise neutral.

    Hope that helps.
     
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  9. Matt_Krush

    Matt_Krush Well-Known Member

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    If you visualize a simple DC schematic...say a battery, a resistor, and an light...current flows from the negative of the battery to the positive.

    Now, 99% of drawings and textbooks show positive flow being outward...but that is not correct.

    Think of the tube amp, 'by making the grid sufficiently negative, we get current to flow from cathode to anode.
     

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