schematicwiring.com

In public address amplifier, feedback is something that have to be avoided. The ideal solution of this is to adjust the speaker position and the microphone. However, many times is not possible doing so. Another solution is to using frequency shifter in order to change the output frequency 10Hz lower than the input frequency. However, for a low cost public address system, this solution is too costly. That why we need Voice operated switch :

LM346 is an op-amp than can be programmed. By pulling the SET pin(s) to V-, it shuts down and its output goes to a high impedance state. Therefore, it also can be used as a low speed analog switch for VOX application.

Inside the circuit diagram above, the first op-amp is the buffer for the microphone with gain = 2. The diode 1N914 and the second op-amp is configured as peak follower. Follow immediately the signal peak but falls down slowly because the charge of the 10uF can’t be eliminated by op-amp output. Then it have to be discharged slowly through 10M resistor to ensure the voice signal is not muted at short silence between sentences and words. The other op-amp, the third, is utilized as a comparator, which its reference is adjustable through 10k potentiometer. To set the proper level where the sound activate this circuit, this potentiometer should be adjusted. The 4th op-amp doing the voice muting, if the control voltage output falls to zero due to no sufficient sound level detected on the microphone. Try to connect the microphone to MIC IN, and connect the audio out to your microphone input of the amplifier. The control output of the circuit is also provided to control other equipment such as the lamps or relays.

Posts Related to Circuit Schematic Voice Operated Switch (VOX) using LM346 for Public Address Amplifier System

Circuit Schematic Diagram of Voice Operated Switch using LM346 IC for Public Address Amplifier System

In public address amplifier, feedback is something that need to be avoided. Of course adjusting the speaker position and the microphone will solved the problem, ...

Flip-Flop Sound Responder Circuit Schematic Diagram

Flip-flop sound responder circuit diagram is a circuit that will create flip-flop output as a reaction from sound as an input. A condenser microphone is ...

Two Transistors Wireless Microphone FM Transmitter Circuit Schematic Diagram

Please be warned if operating this circuit might violate the regulation of your country, because this FM transmitter circuit radiate strong radio frequency to the ...

Speaker Sound Level Meter Circuit Schematic

We can measure the sound level of a speaker using this circuit. When the switch is in OFF close position and the microphone on low ...