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Dynamic range

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WHAT IT TELLS US

This is a measure of noise and distortion below the signal.  It tells us how much rubbish the system is producing, to roughen and muddy the sound. Distortion measurements sum harmonics only, ignoring the quantisation noise that accompanies low level signals in a 16bit system. Harmonic distortion was dominant with early Digital-to-Analogue Convertors like Philips TDA1541 but with modern convertors it is less so, whilst quantisation noise inevitably remains. Dynamic range measurement sums both and gives a truer picture of the level of unwanted hash.


HOW WE MEASURE IT

We measure Dynamic Range to the Japanese EIAJ  (Electronic Industries Association of Japan) standard, using a Rohde & Schwarz UPL analyser. This specifies distortion plus noise are measured using a -60dB test tone at 1kHz, from an EIAJ test disc. IEC A weighting must be applied. The level measured, usually around -38dB, is added to -60dB to give a total dynamic range value. The use of IEC A weighting means frequencies around 1kHz dominate, so this is not a meaningful measure of total distortion plus noise (THD+N).




eiaj-test-disc

 

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