Thd??

Discussion in 'Archived Threads 2001-2004' started by Jon Bye, Jun 3, 2002.

  1. Jon Bye

    Jon Bye Stunt Coordinator

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    What exactly is it? Is there a big difference between .7% and .09 % I am pretty sure that .o9 is better but.....?
     
  2. Bob McElfresh

    Bob McElfresh Producer

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    When you run a signal through an amplifier circuit, the amplification does alter the signal a bit. This distortion has a measurement associated with it.
    But you must realize, a amp/receiver rated at .. 80 watts per channel can produce 90/100/110 amps of power - but at the cost of higher distortion. The increase is geometric, not linear.
    So a maker of cheap electronics can claim to produce a "powerful" 120 watts per channel. But when you read the fine print it has something like "0.7% THD".
    A better unit would be a Yamaha/Dennon producing 80 watts per channel at 0.09 % distortion. This indicates a much better quality set of electronics.
    I believe (running from memory here) that humans can detect when distortion reaches 1-2% at the frequency we are most sensitive to (about 10,000 hz).
    So the THD numbers do 2 things:
    - Allow you to compare the specs from one unit to another. (Dont even try to compare the power ratings between the two units stating 0.09% and 0.7% - they are not in the same class).
    - Give you an indication of the quality of the amplifier section.
    There are a few other fine-print details to look for:
    The power ratings should also say something like:
    20-20,000 hz
    8 ohm resistive load
    All channels driven
    Hope this helps.
     
  3. Jeffrey Forner

    Jeffrey Forner Screenwriter

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