Computer active speakers sold on the market are huge in size and single in function, and the prices are all above one hundred yuan. The active speakers used on the computer do not have too high requirements for sound quality, and are generally used for learning multimedia education CDs, appreciation CDs, and system prompt sounds. I have recently made a cheap computer active speaker, which not only can meet the above functional requirements, but also can be built into the case, and the volume of the speaker can be controlled by a volume switch.
Working principle: TDA2002 is an audio power amplifier integrated circuit. It can output about 3W of undistorted power on an 8-ohm load. It has a variety of internal protection circuits, and it has strong adaptability to abnormal conditions such as current surge, overvoltage and load short circuit. Sexuality, working voltage 8 ~ 18V, quiescent current 4mA, was very popular in the past few years, widely used for power amplification of surround channels, if you were an audiophile, maybe there are a few pieces on hand, Here, referring to the typical wiring diagram of TDA2002, it is connected to an audio power amplifier. In the figure, C2 is the input coupling capacitor, which plays the role of coupling the audio signal, and at the same time isolates the DC component. At the beginning, I did not connect C2, so the speaker emits strong AC sound . C1 is also an input coupling capacitor. It isolates the audio signal of the sound card to the volume potentiometer. The volume potentiometer uses a more commonly used 4.7K potentiometer with a switch. When the volume is turned to the minimum, the power switch can be turned off. C7 and C6 are power supply filter capacitors, which can filter and store the 12V voltage provided by the computer's switching power supply. C7 helps reduce the high-frequency internal resistance of the power supply. There is a lot of interference inside the computer. Switching power supply and digital circuits will produce audio interference. In order to improve the signal-to-noise ratio of active speakers, the passband of the audio amplifier can be reduced. C8 can bypass some high-frequency noise and improve the signal. Noise ratio.
Commissioning and installation: TDA2002 needs to install a 10 cm x 10 cm aluminum heat dissipation plate, and apply appropriate amount of thermal grease to facilitate heat dissipation. After the circuit is assembled, first use an external 12V regulated power supply to turn on the volume potentiometer At the maximum, a slight soft rustling current sound will be emitted from the speaker at this time, and a loud hum sound will be emitted from the speaker when you touch the signal input terminal with your finger, which shows that the circuit is working properly. Connect the audio signal output from the sound card to the input terminal of the power amplifier with a double-core shielded cable, then find a four-hole power plug that is not in use, connect the 12V positive power supply and the ground wire to the power terminal of the power amplifier, the volume potentiometer can It is fixed on the panel of the computer case. Generally, the case has an idle full-high CD reserved position. Usually it is covered by a plastic baffle. The potentiometer can be fixed at the plastic baffle.
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