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my measurements of amplified ear.

Discussion in 'Electronic Basics' started by Johan Wagener, Aug 12, 2004.

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  1. here is my measurements taken on the amplified ear with a 16ohm load
    (one earpiece) connected and a 1.48V battery used as power source

    Q1
    E - 0V
    B - 0.506V
    C - 1.451V

    Q2
    E - 0V
    B - 0.554
    c - 1.342

    Q3
    E - 0V
    B - 0.4V decreasing to 0V (after 1 minute)
    C - 1.37

    Q4
    E - 0V
    B - 0.63
    C - 1.461

    I get a very faint amplification of the mic at the output. Increasing
    battery to 3V gives better amplification but still only blowing into
    the mic or knocking it against the table, and so on.
     
  2. Where is the circuit diagram?
     
  3. I assume he's referring to this one:
    http://www.electronics-lab.com/projects/audio/023/

    I built it out (with real components!) of sheer curiosity and it does
    work fine.
    What are you using for D1? The prescribed part or just any old diode?
    This fault should be pretty simple to find.
     
  4. I read in sci.electronics.design that Paul Burridge
    >) about 'my measurements of amplified ear.', on Thu, 12 Aug
    2004:
    Disconnect Q3 base and D1 from C3, leaving them connected together. Does
    it work then? Check that D1 is the right way round. If you are not sure,
    try reversing it. You can't damage it by doing so.
     
  5. Andrew Holme

    Andrew Holme Guest

    Q2 base voltage sounds low and the Q2 collector sounds high. I've
    just pushed a 2N2222 and a couple of resistors (R4=100k, R5=3k9) into
    a breadboard and I'm getting Vb=0.59V and Vc=0.79V for a 1.5V supply.

    Q3 (auto-level control) is off as it should be when there's no input.

    Q1 base voltage sounds a bit low but may be OK. You might try
    slightly reducing the value of R2, but I would check the circuitry
    around Q2 first.
     
  6. Graham Knott

    Graham Knott Guest

    --

    You haven't by chance connected the top of the volume control to the
    junction of R6/R7. The circuit shows a "crossover" not a join.

    My most up-to-date website
    Electronics for Beginners & Intermediate Electronics
    http://homepage.ntlworld.com/g.knott/index.htm
     
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