double bypass surgery

Discussion in 'Ampage Area' started by Jaybird, Dec 28, 2008.

  1. mugsy

    mugsy Synchromatic

    Nov 3, 2008
    Hi Johnny:

    With a cathode cap, a small value resistor forms the NFB shunt on the ground side of the cathode resistor/cap. (see the AA764 Champ)

    With the cap disconnected, the 1.5k and 47 ohm resistors combine, so there would be a slight difference. The combined total is still within the +/- 5% value of the 1.5k cap.

    Did I misunderstand you?
  2. JohnnyCrash

    JohnnyCrash Gretschie

    Nov 22, 2008
    Fullerton, CA
    Nah, it's been a long week for me. I think I lost more brain cells through the standard stresses of life lately than through the distilled versions... which is new to me. I guess it's time to uncork and get things untangled.
  3. mugsy

    mugsy Synchromatic

    Nov 3, 2008
    Hehehe... I can identify with that. Our little one still isn't sleeping through the night, so I'm feeling a little foggy myself :)
  4. Jaybird

    Jaybird Electromatic

    Nov 2, 2008
  5. mugsy

    mugsy Synchromatic

    Nov 3, 2008
    You actually don't have NFB anymore. With the 22k NFB series resistor on the + side of the cathode resistor/cap combo, you're injecting voltage which is then being bypassed to ground. That's why the gain increase sounds so significant; you're feedback voltage (which is meant to remove gain, etc.) is actually contributing to it.
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