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THD ratings

Discussion in 'Archived Threads 2001-2004' started by Mike Mundt, Mar 23, 2003.

  1. Mike Mundt

    Mike Mundt Well-Known Member

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    Ok, i understand common tests are done to reciever to figure out the harmonic distortion they produce.

    i know they commonly use one test of 8 ohms 20Hz-20kHz to figure out the recievers THD. Then they also do another test at 1kHz 8 ohms to figure out another THD level.

    my question is im looking at the Onkyo TX-NR900 and they give you the information like this
    ----------------------------------------------------------
    THD (Rated Power) 0.08 % (all channels)
    Damping Factor (1 kHz, 8 ohm) 60
    ----------------------------------------------------------
    Is the 0.08% rating a 8 ohms 20Hz-20kHz test?
    What does Damping Factor mean?
    And what is 60 measured?
     
  2. Mike Mundt

    Mike Mundt Well-Known Member

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    *And how is 60 measured?
     
  3. Jack Briggs

    Jack Briggs Well-Known Member

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    • If the Onkyo's harmonic-distortion figures are given as stated in your post then it appears likely the measurement was taken at 1 kHz (which results in a lower figure). The preferred measurement stat would be the harmonic distortion measured across the entire audio bandwidth of 20 Hz to 20 kHz with all channels driven.

    • Damping factor is the value of the output impedance at a particular frequency divided into eight. That measures the amplifier’s ability to deliver a flat frequency to the load. Also, according to orthodoxy, the higher the damping factor the swifter the amplifier's "recovery" from a transient peak.

    This is debatable, however. McIntosh, for example, has long scoffed at the notion that really high damping factors improve transient response (the damping-factor numbers for its transistor amplifiers are more like those of tube amps). My psychological makeup results in my preferring higher damping-factor numbers, though I can't make a case for it. Perhaps somebody else here can.
     

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