Crown FM150, User Manual

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5.15 Audio Distortion
Make distortion measurements from the de-emphasized output of an FM modulation moni-
tor.
Make audio distortion measurements for left and right channels at frequencies of 50 Hz, 100
Hz, 400 Hz, 1 kHz, 5 kHz, 10 kHz, and 15 kHz. See sections 5.9.1 and 5.9.2.
5.16 Modulation Percentage
While feeding an audio signal into the left channel only, confirm that the total modulation
percentage remains constant when switching between Mono and Stereo.
Measure modulation percentage with an FM modulation monitor. See section 5.2.2.
19–kHz pilot modulation should be 9%.
5.17 FM and AM Noise
Take noise readings from a de-emphasized output of a modulation monitor.
5.18 Stereo Separation
Make left-into-right and right-into-left stereo separation measurements with an FM modula-
tion monitor for frequencies of 50 Hz, 100 Hz, 400 Hz, 1 kHz, 5 kHz, 10 kHz, and 15 kHz.
5.19 Crosstalk
For stereo crosstalk measurements, both left and right channels are fed at the same time.
For best results, there needs to be a means of correcting small imbalances in levels and
phase. The balance is made at 400 Hz.
5.19.1 Main Channel Into Sub
Feed the left and right channels in phase with audio (L+R) at 50 Hz, 100 Hz, 400 Hz, 1 kHz,
5 kHz, 10 kHz, and 15 kHz at 100% modulation, while observing the stereo subcarrier (L-R)
level on an FM modulation monitor.
5.19.2 Sub Channel Into Main
Feed the audio into the left and right channel as above, with the exception of reversing the
polarity of the audio of one channel (L-R input). Using the frequencies of 5.19.1 above, ob-
serve the main channel (L+R) level with a modulation monitor.
5-9 Adjustments and Tests