This is a simple audio signal overload protection circuit. Why should you build it? In the standard audio generators, its output level must not exceed 1Vrms. But now, many audio signal generators may produce the signal to over a limited standard level.
Simple audio signal overload protection circuit diagram
It may make a bad result to an input of stereo power amplifier. Which a normal power amplifier need a signal input under 1Vrms.
If it is a higher signal. It still amplifies audio up to a higher level. But the sound signal changes waveform, Such as we feed the input is sine but the ouput is a square wave. We need just the sine wave that is a higher volume on a loudspeaker.
It may make oscillated, too. Which the power amplifier and loudspeaker are damaged.
Thus, this circuit will protect the input of power amplifier away high amplitude, more than 1Vrms.
How it works
If you see the circuit, it may make you smile. It uses 5 components only. Do not wait! Build it! We install it between the signal generator and power amplifier.
When there is an input voltage flows through R1 to limit currents down. Then, the current comes D1-D4, in bridge diodes form. They are full wave rectifier circuit to convert ACV to be DCV.
Because the Q1 is NPN transistor, it likes DCV. But it will start working when the input voltage is more than 1V RMS.
The transistor-Q1 will conduct the current, Between the collector and emitter looks like the short circuit. The input signal cannot come to the output to the input of the power amplifier.
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