Power Amplifier Speaker Protection Circuit Schematic

While switching a power amplifier on, a loud thump sound is heard to sudden heavy discharge current through the speaker at the time of power on. This current may damage the speaker, especially in case of direct coupled amplifier.

PARTS LIST R1 5KΩ Preset C1 1000µF 25V C2 0.1µF (104) D1 IN4001 Q1 BC107 RL1 9V 500Ω Relay LS1 Speaker

The circuit given here protects speakers from the current surge. When the amplifier is off, relay switch is also off. When the amplifier is switch on, R1 and Ci provide delay of a few seconds to switch the transistor on which energizes the relay.

Delay time is proportional to value of R1.

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