6-channel class-D amplifier
Basic operation of a class-D amplifier
Basically, the output stage of a class-D amplifier outputs a continuous square wave swinging between positive and negative power supplies
with a fixed frequency (“clock” frequency) far beyond the audible range. The duty cycle of this square wave is modulated with the audio signal.
The output is followed by a low-pass filter which eliminates the clock frequency and allows only the audio signal going to the speaker. See
simplified drawing below.
Compared to a conventional power amplifier the benefits of the Class-D amplifier are:
• higher effiency
• lower power dissipation
• smaller heatsink required
• smaller mains transformer required
The main disadvantage of this concept is:
• The amplifier is operating with a high-frequency square wave at high amplitude and currents. This requires special precautions to prevent
excessive electromagnetic ratiation (EMC).
6 - channel AMPLIFIER BOARD
(6x 75W)
TABLE OF CONTENT
Class D amplifier circuit description . . . . . . . . . . . . . . . . . . . . . . . . . .83
Exploded view & mechanical parts . . . . . . . . . . . . . . . . . . . . . . . . . .84
Schematic diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .85
Assembly drawing, componentside view . . . . . . . . . . . . . . . . . . . . . .86
Assembly drawing, copperside view . . . . . . . . . . . . . . . . . . . . . . . . .87
Loudspeaker sockets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .88
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