NTi Audio Digilyzer DL1 - Manual (Page 47)

47
THd+N
The THD+N function (Total Harmonic Distortion+Noise) calculates
the deviation of the input signal from an ideal sine wave. This
measurement is most important to check and qualify analog/digital
converters.
The Digilyzer is able to calculate THD+N values down to –100dB
(0.001%). For better THD+N values “< -100 dB“ (< 0.001%) are
displayed.
THd+N results of the selected channel may be displayed in dB or %.
Full scale indication appears whenever one sample reaches full
scale. This indication is independent of the clipping of the PPM
meter.
Filter: The audio signal decoded from the digital audio stream can
be filtered with the following filters prior to the RMS or THD+N
calculations:
• HP400, highpass 400 has a good rejection in the area of main
frequencies – so hum problems may easily be examined and
localized. The HP400 is also used to measure quantization
noise.
• 22-22k, bandpass 22-22k is used to define the commonly used
measurement bandwidth from 22Hz to 22kHz.
Measurement Functions
Fig 5-50, THD + N screen
THD+N
result
Display mode Filter
Fundamental
frequency
Level RMS
Full scale
indication