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Thread: Eliminating Ground Loop

  1. #21
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    Snootch, a square wave isn't clipped, that's just how it looks when you test the audio voltage with an oscilloscope. The regular wave is trying to produce more voltage to complete its sinus rhythm but can't so it flattens out.

    My example of a square wave above is actually a clean, square wave. Did your TV speakers ever blow from playing Super Mario Brothers or Tetris or Duck Hunt? Not unless you had it cranked to some ungodly volume. There's also triangle waves too also referred to as saw waves.


    Just because square wave and saw waves don't look sinus, they still behave as a sinus wave. A clipped signal no longer behaves like a sinus wave.

  2. #22
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    square waves from digital audio sources are very common, but low in amplitude and duration. They are usually less than 6 ms musically before flipping polarity. They also maintain their energy in their designated frequency
    A clipped signal will max out amplitude and extend duration. When the signal clips, it also displaces energy into higher frequencies with just as much amplitude. Your woofer/midbass can handle that 200 watts for extended periods, but after the signal clip, you tweeters are now seeing the energy...

    Clip = distortion = speaker staying at one extreme for two long = dc = bad

    More indepth explanations are available all over the web.

  3. #23
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    Quote Originally Posted by Shadow View Post
    Just because square wave and saw waves don't look sinus, they still behave as a sinus wave. A clipped signal no longer behaves like a sinus wave.
    Nomally I'm not pedantic, but this is driving me nuts! It is *not* a "sinus". A sinus is a cavity in your facial bones. You are talking about sine waves as in the trignometric funcion sine or cosine.

    Secondly, a heavily clipped sine wave is for all intents and purposes equivalent to a square wave. A square wave is the limiting case of a sine wave (ie, the limit as A/L approaches infinity where A is the unclipped sine amlplitude and L is the clipping voltage level).

    Both behave like a superpostion of sine waves (as you've shown in the last diagram), asumming that loudspeakers are linear (which they are not really). Both have very similar Fourier spectra. The sqiggles shown on your sawtooth wave diagrams are waveforms with truncated Fourier series. The fewer harmonics used, the more sinusoidal it looks. It take infinite bandwidth to make a true square or sine wave because the waveforms are not smooth, ie. thier derivatives are discontinuous.

    In any case, they are both probably not good for your speakers. If there is any difference, it's becuase if you have a square wave in a game or bad 80's synth music, it's mixed in with other sounds. If you have a heavily clipped signal, it's nothing but full volume square wave. If you played nothing but square wave (I don't know why anyone would do that), it would have the same effect.

    Anyhow, you've got the right idea to begin with but you might want read up on Fourier theory and linear systems a bit more.

  4. #24
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    si·nus Audio pronunciation of "sinus" ( P ) Pronunciation Key (sns)
    n.

    1. A depression or cavity formed by a bending or curving.
    Sir, the wave is sinus in nature.

    Secondly, a heavily clipped sine wave is for all intents and purposes equivalent to a square wave.
    Will's right:
    square waves from digital audio sources are very common, but low in amplitude and duration.
    If you played nothing but square wave (I don't know why anyone would do that), it would have the same effect.
    So my R-type arcade machine built in 1983 that has an originally equipped and fully functional speaker is an anomaly? What about my friend's MOOG? Is that an anomaly too?

  5. #25
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    Quote Originally Posted by Shadow View Post
    Sir, the wave is sinus in nature.
    Actually, it's sinusoidal in nature. I suggest that you review etymology of the words in question.


    Quote Originally Posted by Shadow
    So my R-type arcade machine built in 1983 that has an originally equipped and fully functional speaker is an anomaly? What about my friend's MOOG? Is that an anomaly too?
    I never said that you can't play a square wave from a speaker. Only that it is not substantially different from playing a heavily clipped sine wave.

  6. #26
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    Hmmm, sinusoidal. Etymology aside, sinus is the ROOT for sinusoidal. The rhythm is sinus. The mathematical function to calculate the actual plot is sinusoidal.


    Need a step stool?

    Only that it is not substantially different from playing a heavily clipped sine wave.
    As far as the o-scope is concerned, you're right. As far as the motor in the speaker is concerned, you're dead wrong.

  7. #27
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    Quote Originally Posted by Shadow View Post
    Hmmm, sinusoidal. Etymology aside, sinus is the ROOT for sinusoidal. The rhythm is sinus. The mathematical function to calculate the actual plot is sinusoidal.


    Need a step stool?
    Very cute. At least I know WTF I'm talking about. Nobody but you calls it a "sinus wave". If English is not your first language, I appologize.

    Quote Originally Posted by Shadow
    As far as the o-scope is concerned, you're right. As far as the motor in the speaker is concerned, you're dead wrong.
    I'm just a dumb electrical engineer. Please explain the difference in terms that an engineer can understand.

  8. #28
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    Quote Originally Posted by Shadow View Post
    What about my friend's MOOG?
    MOOG's are awesome. My friends dad had one. He sold it on ebay for like $600 dollars

  9. #29
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    The oscilloscope just reads a circuit and displays the freqency and amplitude on the screen. The oscilloscope doesn't care what the wave looks like. A normal 60Hz sine wave looks about the same as a heavily clipped 60Hz sine wave.

    Now, take your 60Hz sine wave and turn it into a square wave which is almost the equivalent of a digital signal. Hook it up to an AC motor and then explain to me why the motor doesn't work the same as it did with the sine or clipped sine wave.

    They appear almost the same on equipment but are completely different to a motor.

  10. #30
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    Quote Originally Posted by Shadow View Post
    The oscilloscope just reads a circuit and displays the freqency and amplitude on the screen. The oscilloscope doesn't care what the wave looks like. A normal 60Hz sine wave looks about the same as a heavily clipped 60Hz sine wave.
    Dude, I know what an oscilloscope does, I use one every day. A 60 Hz sine wave does not look "about the same as a heavily clipped 60Hz sine wave" if the scope has sufficient bandwidth to display a reasonable number of harmonics in the clipped sine wave. They look totally different. The clipped sine wave looks clipped!

    Quote Originally Posted by Shadow
    Now, take your 60Hz sine wave and turn it into a square wave which is almost the equivalent of a digital signal. Hook it up to an AC motor and then explain to me why the motor doesn't work the same as it did with the sine or clipped sine wave.
    The motor *will* work the same with a heavily clipped sine wave and a square wave. That's what I've been saying. Of course, it will be different from a pure sine which is a very different waveform.

    Quote Originally Posted by Shadow
    They appear almost the same on equipment but are completely different to a motor.
    You have yet to explain how they are "completely different" to a motor. You are just saying they are. They look the same on a scope because they are the same, in the limit as the ratio of the unclipped amplitude to the clipping voltage gets very large.

    Do you know the easiest way for generating a square wave from a pure sine wave? You clip it heaviliy using a high bandwidth comparator. This is commonly used for generating digital sync sources from high stability oscillators.

    Look, I'm not trying to beat you up and I'm not on a high horse. You told the original poster about clipping and supplied some nice diagrams, which is good. However your inability to explain the difference (or similarity) between a strongly clipped sine wave and a square wave leads me to believe that you have no real knowledge of EE. In fact I'd be surprised if you've graduated high school. It sounds like you are just repeating stuff that you've heard and do not comprehend any of the theory behind it. That's fine, but you have to know when you don't know something or you'll never learn anything new. Take my earlier advice and look up Fourier transforms and signal decomposition.

    This thread is getting silly and there seems to be nothing that I can do to convince you of some very simple engineering realities. I'm done arguing about it.

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