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Question on audio transformer

  1. Mar 4, 2010 #1
    Will an audio transformer pass multiple signals at the same time to the secondary winding. For example if there is 200Hz 300Hz and 1000Hz on the primary winding, will there be 200Hz 300Hz and 1000 Hz on the secondary. In my opinion it will but I just wanted to confirm this.
  2. jcsd
  3. Mar 4, 2010 #2
    Yes, but remember that the transformer's impedance is frequency dependent. That means that each frequency going through will experience different attenuation and phase shifting.

    Transformers are mutual inductors. Inductors block high frequencies because the impedance rises with (f). Also, transformers cannot transmit a DC current. That means that transformers will tend to block really low frequencies and choke higher frequencies.
  4. Mar 4, 2010 #3
    You did say an audio transformer, so the transformer should be designed to have a reasonably flat response within the audio range.
    It will also be able to pass an audio signal, which usually comprise many frequencies jumbled together, as faithfuly as possible.

    So I would not be worried about passing a few combined signals.

    However, as Oke says, it is impedance that is important with audio tansformers. Their usual purpose is impedance matching between parts of a circuit that have vastly different and incompatible impedances such as a mcirophone or record pickup and an amplifier input or a loudpeaker and an amplifier output. The source and load impedances are important factors, rather than input and output voltages or currents.
  5. Mar 4, 2010 #4
    So if I connected the primary winding to a signal generator, there should be a signal on the secondary winding.
  6. Mar 4, 2010 #5
    Yes I would expect to see a signal, but it rather what signal rather depends upon the transformer and the signal generator. You would also be well advised to create a suitable terminating pad for both the transformer input and output.
  7. Mar 4, 2010 #6


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    Staff: Mentor

    Yes. It will either be in phase or 180 degrees out of phase, depending on how you hook up your 'scope probe and ground clip.
  8. Mar 4, 2010 #7


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    Science Advisor

    The secondary can only have one voltage across it at a time, so at any one moment, you would just see the resultant voltage of the three output frequencies.

    If you looked at it with an oscilloscope, you would see a complex waveform, not the individual sinewave inputs.
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