[Photo] Simple wireless karaoke singing microphone
The microphone is indispensable for karaoke. If you change the wired microphone to a wireless microphone, you will be more at ease when you sing. Whether the microphone introduced in this article is held by hand or put down, it will not have frequency deviation, and the cost is low. Simple and easy to make.
Working principle: The working principle of this microphone is basically the same as the common wireless microphone circuit, but the connection and sound quality are greatly improved. See the attached circuit for the circuit. V1 and L1, C2, C3, etc. constitute an FM high-frequency oscillation circuit. Adjusting the value of L1, C2 can change the operating frequency. C3 is the feedback capacitor to maintain oscillation. The microphone signal is not input from the base of the triode as before, but the microphone is connected to the emitter. When the microphone self-inductance current changes with the size of the sound, the working current of V1 will also change, and the capacitance of the V1 section Cbe changes at the same time. , Cbe and C1 are connected in series and then in parallel with the LC circuit, therefore, frequency modulation is achieved. This connection method of MIC completely avoids the distortion of the audio signal through the coupling capacitor. Therefore, this microphone has a wide frequency response range, pure sound quality, and stable operation. Even if you touch the antenna, it will not affect the LC oscillation frequency.
Component selection production: Oscillation tube V1 selects high frequency tube with fT> 1000MHz, Icmâ‰¥100Ma, and large Î² value, such as C3355, C3358, BFR96, etc. The Icm of the 9018 is only 50mA, but it can be selected according to the actual situation; the MIC uses a 600Î© dynamic coil microphone, and most of the current high-end wired microphones are of this type; the L1 inner diameter is 5mm, which is formed by winding a 5T Î¦0.5mm enameled wire hollow core; You can use the finished antenna directly, or you can make your own: the inner diameter of the coil part is 1cm, the hollow core is wound around 15T and elongated to 3cm, the straight part is 7cm, it is made by heating on a heat shrinkable plastic suit, or a flexible wire of about 10cm can be used instead.
Installation and commissioning: After the components are installed and checked, the power is turned on and a pocket FM radio is used as the receiver. It is worth noting that the VCD with radio frequency output seriously interferes with the reception effect. Therefore, it is necessary to install a power switch on the radio frequency modulator and use the AV terminal to play the program. Adjust the FM receiver and L1 turns to make the transceiver frequency correspond, and change C2 if necessary. The audio signal output by the radio is sent to the VCD or amplifier by a large plug for power amplification. The transmission distance has a great relationship with the sensitivity of the radio, but it is generally â‰¥ 10 meters.
â€”â€”Source: "Electronic Production" Liu Guolun Wu Ruyun
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