Panasonic SA-HT640WPL Service Manual page 24

SA-HT640WPL
8.3.5. What are the potential problems of a Class-D amplifier based system?
The two most common issues of class-D amp system are AM interference and EMI. The switching frequency of class-D ranges
from 300kHz to 450kHz typically 315kHz. The harmonics of such switching frequency will fall into the AM band of 600kHz to
1710kHz. To avoid interference, it is recommended to have a variable switching frequency adjustment circuit [usually known as
beatproofing in PSG). Systems without AM tuner are not required to have such circuitry.
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