Carbon Composition, and Series Resonance

Discussion in 'Homework Help' started by CiaranM, Oct 4, 2012.

  1. CiaranM

    Thread Starter New Member

    Jul 15, 2012
    25
    2
    Hello! I was reading up on carbon composition resistors, to see whether they're as good as audiophiles would claim. According to this page http://www.geofex.com/article_folders/carbon_comp/carboncomp.htm, high voltages are needed before harmonic distortion is noticeable. Could I therefore connect audio to a step-up transformer, put a carbon comp in series, and use a transformer with the same ratio (but as a step-down) after the resistor and achieve suitable distortion?
    PS. a transformer increases V or I while decreasing I or V in proportion. Is that right??

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    One of my tutors said that the voltage drops in a series resonant circuit are higher than the supply voltage. How is this possible if a capacitor and inductor are passive components? I read that at f.res the 'impedances cancel out'. How is it possible for series resistances to cancel out?
    I've included a li'l circuit, you can use it to explain this.
    thanks!
     
  2. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    An ordinary single transistor produces "mojo" 2nd harmonic distortion when it has no negative feedback and the output level approaches the supply voltage.
    Then you don't need transformers and antique resistors.

    I had a 220VAC fan but my electricity is 120VAC. So I connected a capacitor in series with the fan and it ran fine on 120VAC. I measured 185VAC across the fan.
    The capacitor tuned the series LC circuit to resonate at the mains frequency.
     
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