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Audio Generator

Discussion in 'Electronic Basics' started by James Douglas, Feb 4, 2006.

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  1. Building a project which requires alignment and says to use a audio
    generator, which basically looks like a function generator, which I
    do have. For various sections of the alignment it states, set the audio
    generator to 455KHz, etc.

    Are they one in the same? I am thinking that the audio generator has
    some type of "noise" which the function generator does not?

  2. Ralph Mowery

    Ralph Mowery Guest

    When you get to 455 khz I would think they would say RF generator.
    Anyway, an audio generator is usually tought of as a signal generator that
    goes from around 20 hz to maybe 100 khz or less. If you set your function
    generator to a sine wave function and to the correct frequency and output
    level it will work just as well. You may think of the audio generator as
    just part of the function generator. Function generators usually have more
    options than the audio generators.
  3. I would expect an audio signal generator to just produce sine waves
    over a range of 10 - 30,000 Hz, or so. A signal generator for 455 KHz
    would more likely be called an RF signal generator, and would only
    make sine waves.

    A function generator would produce signals from 1Hz (or less) up to 20
    - 50 MHz, and should be able to produce sine, square or triangle
    waves, or pulses. A function generator should be able to replace an
    audio or RF generator in most applications (up to its maximum

    An audio generator may have lower distortion on its sine wave than the
    function generator, which may be significant if you are doing
    distortion measurements

    Peter Bennett, VE7CEI
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  4. Bob Eldred

    Bob Eldred Guest

    It's a matter of how the signals are generated. An audio generator usually
    uses a sine wave oscillator such as a Wien Bridge to generate its signals
    while a function generator uses integration and rounding of a sawtooth wave
    to generate its sine output. There are subtle differences in the distortion,
    points of inflection and other issues than distinguish the waveforms. None
    of that should matter to you as long as you can get a stable, accurate
    frequency. Most function generators don't have very precise frquency setting
    knobs making it hard to get an exact frequency setting. You should use a
    counter to set the frequency as closely as possible. This frequency, 455KHz
    is the I-F frequency for a standard AM receiver. It should be accurately set
    to avoid spurious responses and other problems.
  5. Pooh Bear

    Pooh Bear Guest

    Audio sig gens wil certainly have sinewave and usually square wave outputs.
    Function generators will normally have triangle and pulse outputs too and
    maybe a mark-space adjustment.

    A 'noise generator' is another thing altogether.

  6. Bob Masta

    Bob Masta Guest

    To extend what others have already said, note that
    function generators intrinsically produce triangle
    (and square) waves, and have to be shaped to sine
    waves. The sine wave distortion is typically 1%.
    An audio sine generator typically has distortion below
    0.1% in the 20-20000 Hz range. Usually, either
    type is limited to a MHz or so.

    If you need a signal generator for conventional
    audio frequencies (20-20000 Hz), you might want to
    check out my freeware DaqGen signal generator
    software. It can use any Windows computer and sound
    card. Sine distortion is limited by the card, but can
    easily be better than typical benchtop models.
    Besides sine waves, it can create most any waveform
    you need, including different types of random noise and
    arbitrary waveforms. You can combine 4 separate streams
    per output channel, and each stream can use any or all
    of several modulation types, including Burst, AM, FM, PM,
    or Sweep. I'd be glad to answer any questions about it.

    Best regards,

    Bob Masta

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
    Home of DaqGen, the FREEWARE signal generator
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