Audio limiter is use to limit the audio signal to a desired value. In many audio devices we feel the need of audio limiter. Listening a radio and searching for stations on the radio dial provide fun but on short wave band not every signal is equal some are weak signals containing low gain and
some are strong signals high gain when we tune a strong and high gain signal on shortwave band then the output of audio increase due to the high gain of strong signal. When we listening a weak signal and move to a strong signal in radio dial will makes ears shocked due to a very loud volume suddenly. So the audio limiting device will solve this problem by limiting the audio to a desired value. The two silicon diodes are used in this circuit to limit audio signal going to the headphone. These silicon diodes do not conduct in forward position if the voltage is under 0.6V. Therefore the presence of diode 1 and diode 2 does not affect the volume going to headphone when the peak signal amplitude is lower then 0.6V. Above 0.6V the D1 and D2 conduct heavy signal dropped across resistor 1. Volume will adjust by volume control R2.