Four choices an audio switching circuit ----- Audio Signal Selector

Author: Cheng Yuan This four selection of audio switches are improved by small batches. It can be used in small closed-circuit systems, venues, teachons, weddings, etc., with image output level adjustable, clear sound, no striking multi-purpose output. The line is divided into two parts: the above picture shows the video and audio switching circuit, and the picture below shows the viewing audio allocation amplifier circuit. In the above figure, switching is controlled by the four D trigger CD40175 (1C1). The control signal controls the transistors BG1 to 4 and BG6 to 9. BG1 ~ 4 make video switches, BG6 ~ 9 as audio switches. The role of the BG5 video shifter is mainly to reduce the capacity of the video input coupling capacitor and make the input device connected to the output easily impedance match. The (2) feet of the CD40175, (7) feet, (10) feet, (15), when the foot is high, the switch tube BG1 and BG9, BG2 and BG8, BG3, and BG7, BG4 and BG6 will be respectively All the way is saturated, the video signal is transmitted by the triode collector to the emitter, and then the channel signal is output after the primary sessile BG5. The audio signal is passed through the triode collector to the emitter, and the audio signal is directly outputted. When the k1 is pressed, the (2) foot outputs high level, the BG1 and BG9 are turned on, and the video signal V-IN1 is transmitted to the BG5 base by the BG1 collector, and the emitter output is output from the emitter; audio signal A-IN1 is output by the BG9 collector and the emitter output. The circuit is not used in the CD4066 four-way analog switch because it is used as a switch, it is found that when the signal input level is large (such as the audio output of the VCD machine), a more severe string is generated, and it is estimated that it may be The internal simulation switch is closer to the distance. C3 is used in power-on, and the circuits k1 ~ k4 are single button switches. The audio amplifier circuit part uses TL084 high-speed four op amps, one of which is pre-pre-pre-pre-prevention, only 3 times the input signal, and other three ways are used as an output shot. The BG3 and BG4 requirements in the video signal amplifier circuit shown below require that the RW1 is adjusted as an image output level. The output can be at least three TV loads, all the way to the modulator, all the way to monitor, all the way. The entire circuit is very simple, and the frequency bandwidth, the frequency response is straight, the insertion loss is small, but the work is reliable and the performance is good.

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