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How To Combine Two Audio Output Transformers

Discussion in 'Electronic Design' started by Fulton, Dec 17, 2007.

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  1. Fulton

    Fulton Guest

    I have two audio transformers that each have a 2H @ 300 Hertz primary
    and a 8 ohm secondary for a speaker. Can I combine them in series to
    get 4H primary? How would I combine the secondaries?
  2. Eeyore

    Eeyore Guest

    What a strange thing to do.

    Why do you think you need a 4H primary ? And why are you mixing up
    recommended loa impedance specs with winding inductances ?

  3. Fulton

    Fulton Guest

    I have a tube amplifier with a final stage (pentode) that needs about
    a 10,000 ohm load. At 300 hertz this is equivalent to about 5 or 6
    Henries. So I want to use some AF transformers that I already have.
  4. Nobody

    Nobody Guest

    So you want to match an 8Ohm speaker to 10KOhms? In which case, you need a
    35:1 transformer (sqrt(10000/8) ~= 35.4).
    The inductance of the windings doesn't come into it. A transformer doesn't
    behave (much) like an inductor if the secondary is loaded.
  5. Phil Allison

    Phil Allison Guest


    ** Output transformers for single tube amplifiers are *specially designed*
    to handle the DC current that must flow all the time - ie there is a
    deliberate gap between the E and I laminations.

    ** Normal transformers will magnetically saturate with DC current flow so
    results will be very poor.

    ........ Phil
  6. Tim Williams

    Tim Williams Guest

    It sure does below 300Hz (in this case).

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