Gelin9658H Green Sound has a radio (FM, SW and MW band), tape recording, ramock, karaoke, tone control, ultra-low, all-way, source input, and light display. Speaker is two unit combinations: the low sound speaker is a Green brand YD166-2A6 eraser speaker, the treble speaker is a long-awaited YDG50-1A2 paper basin speaker. The shape of the speaker is 540 (high) × 250 (width) × 210 (deep) mm. The speaker box is made of medium density plate, and the front plate thickness is 13mm, and the remaining plate thickness is only 7mm. The frequency division function is only completed by a 4.7 μF general electrolytic capacitor. The FM band has automatic static noise. The author has made this combined sound as follows: (1) Keep all the sound source parts, reserved the front level of the tone control. In order to increase the reception sensitivity of the FM wave band, increase the indoor sheep antenna (idle after the TV is changed), and can also have an outdoor antenna to improve the number of reception modulators; (2) ultra-low sounds cause distortion, not used after transformation; (3) The original power discharge IC is TA7270, the power is small, the decision is not used, add new power generation circuit; (4) speaker transformation. The new power discharge circuit of the new power discharge circuit is shown in the figure. Only one channel is plotted, and the other channel is the same. LM1875 is a single 30W power integrated circuit, the US National Semiconductor Company (NS Company) product, is known for the sweetness of sound quality, and it is often used in foreign well-known AV amplifiers, and is a preferred device for amateur production power amplifiers. When using LM1875, the author has made "DC servo current negative feedback power", which sounds full of thickness, and the lifetime of the bass improvement is improved to some extent. However, the component data given by the information should be greatly adjusted and to increase the auxiliary circuit to eliminate high frequency self-excitement, which is very difficult for amateur production. Thus, the author decided to cancel the feedback capacitor (22μF grounding capacitance) according to the characteristics of the LM1875 output offset voltage, so that the frequency response to the DC, and eliminates the signal phase shift from this capacitor. Linear distortion, power amplifier. The power discharge circuit is stable and reliable, and the sound quality is greatly improved, and it is also suitable for amateur production. Of course, the circuit is stable and reliable is prerequisite with high quality power and peripheral components. This amplifier adds 1 100W transformer, and the original transformer is designed for pre-serialization. All resistors use NEC's five-color ring resistance, small capacitance, select CBB model, and input capacitors use tantalum capacitors. The new power discharge board and the transformer place the bottom space in the box and maintain an appropriate distance between each other. Add a double knife double throw switch, in the box, used for the source switching. Welding the original box, the source input line is welded from the front stage circuit, connected to one end of the double throw switch, so that the external quality sound source is directly released, without human modification, meets Hi-Fi requirements: connect the original tone circuit to the potential The signal line of the unit is welded from the potentiometer, and then connected to the other end of the double throw switch, and then put the output line of the potentiometer from the original power to this instance. Connect the active place and the original power supply ground. The original volume potentiometer has difficulty eliminating noise, exchange APLS50 × 2 potentiometers. Disconnect all the connection to the original power, and the original power is released. Speaker renovation makes two two-frequency 6dB divider (DV frequency 4000 Hz) for replacing two 4.7 μF capacitors. The original low-sounding speakers and treble speakers can be reserved compared to the commercially available general speaker speakers due to its actual performance. The box wall is so thin, and the transformation step is as follows: Open the rear cover, the inner wall is reinforced with this strip, and then store small nails, evenly apply 5 mm thick cement concrete, so that the wall thickness, the second is to increase the weight, Reduce the box and improve the sound quality. Then the 15mm thick sponge, the last loaded cover, and sealed with a glass glue. The original connection sound box line is a normal thin line, and the municipal speaker cable is changed. After completing the above steps, the test machine, the double throw switch is pulled down, and the source input is input. You can listen to the FM quality music broadcast; the switch is pulled, connecting the VCD, playing the "Titanic" singing in Dion. Theme "My Heart Will Go On". The beautiful and beautiful melody is a heart-drunk, and the rich tone is very good. Finally, in order to prevent the VCD signal voltage from being too large, two 150kΩ resistors are connected in series. The above renovation cost is only more than 2 million yuan, but the reconstruction of the sound performance can be used in a multi-diverse amplifier, and the speaker can fully meet the requirements of the general family to build the home theater, it is a better method for the transformation of ordinary combined speakers. . Technology area
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