Bookshelf active speakers 03

The simplified diagram of components and internal functions is shown in Figure 9-50. c, i, and C2 are the feedback capacitor t. Changing the capacity can change the low-frequency cutoff frequency within a certain range
. C30 and C5 are the output coupling capacitors. Under normal circumstances,
increase to 4 7 0r.rF is sufficient. C6.C 7 are vibration damping capacitors, which
may not be used if there is no impact. C3 is the power supply decoupling capacitor and should be increased as much as possible. TDA2822
is a dual power amplifier integrated circuit. When the power supply voltage is Vc-6V, RL. 18fl
. When THD=10%, the output power of each channel is 1000mW.
During normal operation, the quiescent current is very small, only about 8mA, and there is an internal load short-circuit protection circuit port.
    It is considered to be portable and easy to use in areas with frequent power outages. It is active. The speaker is equipped with a battery box that can hold 4 AA batteries
. In addition, for ease of use, you can purchase a set of rectified power supply as shown in the circuit in Figure 9-52 to power the active speaker. The speaker
already has an external power supply. Switch, when not in use, turn the switch to the left, that is, disconnect the power supply
    . When it is suspected that there is a problem with the quality of TDA2822 , you can measure whether the voltage of pins ① and ③ is 1/2Vc. There is also a light-emitting diode on the speaker
, which has higher power. At this time, the brightness of the light-emitting diode will flash one after another according to the intensity of the music signal.
    Another type of active speaker is shown in Figure 9-53. The speaker has an all-plastic structure, and the volume control and power switch are integrated on the upper part of the box.
In the figure, the 100n.3.3kfl and 2.7kfl resistors form a simple surround sound circuit, as shown in Figure 9-54. The left and right channels are each taken out.
The signals cross-amplify each other.