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Discussion in 'AV Receivers & Amplifiers' started by tk2001, Jan 16, 2002.

  1. tk2001

    tk2001
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    I posted a topic on the 'Sound & Vision Online Forums' because I too thought that somehow my Marantz SR-5200 was underpowered and someone emailed me reply in regards to the SR-5200 alledged 'low output level':

    "Your question about the Marantz receiver being underpowered is interesting. I happen to be looking at the 5200 right now to replace an old unit I have at home. I was interested in the display of power level in dB rather than in some percent of possible output.

    You are not actually running your amplifier at about 70% to drive your speakers at a reasonable level. Actually, you are running it at about one-half percent (.005) of its available power or about 0.5 watts per channel. The reason for this is the use of the decibel scale for power measurement. The number of decibels in the range of the display just happens to be about the number of
    watts in the amplifier output. That's as far as the correlation goes. When you say you have to run the system at about 70%, I assume you mean that the output indication is about -12 dB.

    Power levels and decibels have an approximate relationship of 3 dB for each factor of 2 in power level. That is, if you want to double the power output, you must increase the dB level by 3. To quadruple (doubling a double), you must increase by 6 - etc. Assuming +15 dB is the full power output of the unit and
    you are running at -12 dB, there is difference of 27 dB between your output level and the maximum. Dividing 27 by 3 gives 9 "doublings" or 2 to the ninth power. This is a factor of 512. In other words, you are driving your amplifier at one five-hundred-twelfth of its potential or much less than one half watt.
    Your earlier 7 watt amplifier could also easily handle one half watt."

    Well, the person who emailed me sounded as if he knew what he was talking about. I hope this sheds some light on how dB is measured.
     
  2. Reiner

    Reiner
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    I don't know if you owned an AV amp before but it is correct that the volume knob must be turned up quite high when listening to DD/DTS sources as compared to e.g. CD.
    This is due to the fact that movies feature a very wide dynamic range and are recorded (mastered) differently.

    For proper listening (movies) I must set mine to the 11-12 o'clock position (12 would be half way up), 9 is just fine for tuner or CD. And surely my amp has enough power.

    If you think it's too loud or you watch late at night set the "Dynamic Range" (sometimes also called Midnight Mode or something like that) to STD or MIN. MAX would represent the sound as originally recorded, well, as intended by the sound engineer. Not always healthy but it's more fun ... ;)
     

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