If you have run the two previous tests, and found that the dominant
source of unwanted sound is neither hum nor distortion, it must be
either random noise or interference. To distinguish between these two,
run a spectrum-analysis sweep. To do this, change to the AMPL
measurement function and choose the SELECTIVE filter using the
bottom left soft key. Make sure the analyzer is observing the input
signal and turn off the fundamental tone. Then press SWEEP to pull up
the sweep panel, set the upper and lower frequency limits (preferably
to same limits as the bandwidth of your THD+N measurement), and
run the sweep. You may need to adjust the upper and lower graph
limits as well.
Choose the largest number of points available (150) and run the
sweep. This sweep will tune the bandpass filter to each frequency and
measure the amplitude of signal at that frequency. While the bandpass
filter is too wide for extremely precise results, it may still reveal the
source of the unwanted sound. Wherever there is a significant
interference source (including hum), you will see a peak in the graph. If
the signal is dominated by random noise, it will be essentially smooth.
FUNCTION Descriptions Understanding THD + N
4 Functions
ATS-1 Access User's Manual 4-21
To Next Page
Loading...
Need help?
General
