how does the negative feedback work on the princeton, princeton reverb, and champ with cathode bypas

Discussion in 'Amp Tech Center' started by peteb, Oct 15, 2019.

  1. peteb

    peteb Friend of Leo's

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    the cathode has a cap on it. Doesn't that clear the AC off the cathode?




    princeton_aa964_schem.gif
     
  2. mgwhit

    mgwhit Tele-Holic

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    The cap doesn't clear anything. AC still has clear exposure to the cathode.
     
  3. peteb

    peteb Friend of Leo's

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    A cap is a path to ground for AC.
     
  4. Bendyha

    Bendyha Friend of Leo's Silver Supporter

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    :rolleyes:......:confused:.....?
     
  5. elpico

    elpico Tele-Holic

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    Every cap? Or only ones that are actually connected to ground? Have a second look at where that cap is. It prevents ac from appearing across one resistor. As it's not placed across the one that goes to ground it can do nothing to prevent ac from appearing there.
     
  6. peteb

    peteb Friend of Leo's

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    Thanks Elpico, that makes sense.



    just restating


    there is AC at the junction between the resistors, and the bypass cap ensures that the voltage at the cathode is the same as at the junction.
     
  7. Uncle Daddy

    Uncle Daddy Tele-Holic

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  8. Bendyha

    Bendyha Friend of Leo's Silver Supporter

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    Wrong again. If that was the case there would be no bias between G & C.
    The cap insures that the AC signal at junction and cathode is the same. (except for a frequency related phase shift)
     
  9. peteb

    peteb Friend of Leo's

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    isn't that what I just wrote?
     
  10. Bendyha

    Bendyha Friend of Leo's Silver Supporter

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    That bit yes.
    This bit no.

    The bypass cap ensures that the voltage at the cathode is not the same as at the junction.
    The bypass cap ensures that the AC signal at the cathode is (almost) the same as at the junction (with previously mentioned exceptions).
     
    Last edited: Oct 16, 2019
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