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Maximum wattage, 2 6V6 in PP, cathode bias

Discussion in 'Amp Tech Center' started by jhawk, Sep 20, 2017.

  1. Bendyha

    Bendyha Friend of Leo's Silver Supporter

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    If you bypass the bias resistor with a cap, as is often seen in HIFI cathodynes, then AC passes the resistor through the cap, the resistor doesn't know it is there, it still thinks the dc voltage it is dropping is the 1V bias....and it is right...the bias stays 1v. AC voltage can swing up and down 60V without changing the bias at all, the same as if the cathodyne was fix biased with a negative grid supply.
    The grid curves you see on a normal tube "Average PLATE Caracteristics" graph (which I hope you know what they look like) relate to us what the tube is doing to the plate current and voltage under varying tube grid bias voltages IN RELATIONSHIP TO A GROUNDED CATHODE. This is fine for you standard tube working as a you think they should.

    But triodes have three conections PLATE, GRID and CATHODE.

    Working tubes can put the input signal into the grid, and AC ground the cathode, output comes out of the anode resulting from the changes over a grounded load......normal gain stage

    Working tubes can put the input signal into the grid, and AC ground the anode, output comes out of the cathode resulting from the changes over a grounded load....normal cathode follower......redraw the chatacteristics curves.

    Working tubes can put the input signal into the grid, and AC ground niether anode or cathode directly, both have a signal resulting from the changes over a grounded load...normal cathodyne PI.......redraw the characteristics curves.

    Working tubes can put the input signal into the cathode, and AC and DC ground the grid, output comes from the anode ...normal grounded grid stage.

    Then... there are more... there are combinations....some sitting ontop of others....some just following after each other... some AC conected....some DC conected.....some feeding back positive signals.....some feeding back negative signals.....some doing both....some have AC bypassing of loads...some only at certain frequencies....some draw grid current for part of the duty cycle with out and detrimental negative effects...

    and, and, and.......

    "Without a negative grid at idle you would have automatic and immediate red plate."
    No, it depends on how the tube is set-up. A preamp tube can work very well at the job it has been assigned, if it is set-up correctly, - with no negative grid bias at idle. It will redplate with any grid bias, positive or negative, if set-up wrong. It will not redplate with any grid bias, positive or negative, if set up right. (although sometimes this might be a bit tricky, but being outside of the designed standard working conditions, it is irrelevant) One variable, such as bias, has no functional atribute or meaning without all the other possible variables being taken into account, defined and related to eachother within a circuit.

    Peteb....there are so many ways of utilizing a tube. But you seem to have taken the standard voltage amplifying stage as the defining standard. As the only set-up.

    There is so much more out there for you, and all of us, to learn. Don't limit yourself to one single function. You are suffering from blocking distortion - unblock.

    We know it is hard for you to understand, many of us have tried to explain, but the standard explinations are something that you said once in one of your posts are not what you wanrt to hear. The problem is....that for standard electronic functions, there are standard explinations, that are very simple, functional, and it seems for 99.9% of people sufficient to understand.

    A spade is a spade....most people soon realize how a spade works. But it seems you are not willing to get your own blisters finding out...and quite honestly...i'm sick and tied of digging holes for you to keep saying I should be using a shovel, and I refuse to explain the functions of hole digging in easy to understand words that other hole diggers don't use to explain the duty to navvies, and best with explanatory graphs. (most navvies just get a spade thrown at them, and then are pointed in the right direction.)
     
    Last edited: Sep 26, 2017
  2. Commodore 64

    Commodore 64 Friend of Leo's

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    Being contrary for the sake of being contrary. And then adding gratuitous spaces to call even more attention to the vacuous content. Enough.

    I took 2 pages off of this thread using the ignore button. First time ever.
     
    Jinglehammer and robrob like this.
  3. Bendyha

    Bendyha Friend of Leo's Silver Supporter

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    Sorry C64, You are right, it is all rather annoying, I would rather let it all drop, and shall, but I felt the need to defend the continued attemps to falsify all the work I did on cathodyne PI's and what I have written. Why peteb is choosing to keep cutting at it's credability on this thread, dispite repeated pleads to move to his own thread, I don't know. So I admit to posting many posts irrelevant to the thread theme, and shall now log out, this is my last.
    As you say...Enough.
     
  4. Commodore 64

    Commodore 64 Friend of Leo's

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    No worries, man. I threw in the towel earlier than you, is all. Ha.
     
  5. Old Tele man

    Old Tele man Friend of Leo's

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    Correct!

    AC-signal is like "waves" in the ocean and "ripples" in a pond...where the DC-bias is the nominal "still" water ocean or pond level, ie:

    "waves(AC) on the ocean(DC)"

    "ripples(AC) in a pond(DC)"

    "signal voltage(AC) on a bias voltage(DC)."
     
    Last edited: Sep 26, 2017
    robrob and jhawk like this.
  6. jhawk

    jhawk Tele-Meister

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    Thank you Bblumentritt! Very helpful.

    Thanks to everyone's replies...haha I didn't think this thread would end up opening such a can of worms. I will revisit [parts of] this thread as I press forward. Many thanks!
     
  7. LudwigvonBirk

    LudwigvonBirk Tele-Holic

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    Please don't go away. You are a fascinatingly erudite poster with a lot of very valuable knowledge, in addition to your good verbal posture.

    (Your profile says "Northern Germany" but I will hazmat a guess that doesn't mean Prussia where my Papa on out are from, you seem more sensitive and poetic than that. Are you Parisian?)
     
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