In Reply to: Re: Really? posted by guyser on April 22, 2006 at 12:12:12:
Do a Google search on "Fourier analysis," and pick the result with the level of mathematical detail you desire.For your immediate question, there are two issues. First, a capacitor-input linear power supply, as found in many home audio components, draws current in sharp pulses when the power voltage waveform is near its positive and negative peaks. The sharpness of these pulses, and the very sharp reverse pulses from stored charge in the rectifier diodes (assuming they are not vacuum or Schottky), requires many higher-frequency Fourier components. All the wiring that feeds the component has to accommodate these higher frequency components. The parasitic impedance of that wiring converts these into noise voltage.
Second, the audio signal is present at a low level on the filter capacitor, since it does not have infinite capacity. While the rectifier diodes are conducting, they couple this voltage back to the power wiring. I don't know how significant this is, or whether it makes any difference in performance of power cords and house wiring. In my experience, the RF resonance and transmission characteristics of the audio power cords are the most important features, assuming adequate conductor cross-section for the task.
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Follow Ups
- Anything not a sine wave has higher frequency components. - Al Sekela 14:59:10 04/22/06 (0)