speaker protection circuit for diy car amp

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In general, DC offset protection circuits monitor the DC level across the speaker terminals. The circuits generally have a resistor connected from the active speaker terminal to a capacitor. During normal operation, the capacitor remains discharged because the resistor is constantly charging and discharging the capacitor as the waveform swings from positive to negative between the rails. When there is a DC fault, the resistor is able to charge the capacitor because the voltage goes from be AC (normal) to DC. When the voltage across the capacitor reaches a certain threshold, it triggers the shutdown circuit. For car amps, the most common protection circuits shut down the power supply.

There is an IC that's been used in many home audio amps that could be used in car amps (and may have been used in some of the Japanese amps). It's the UPC1237HA. The datasheet has a sample circuit.
 
simple way, would be the capacitor/resistor triggering a transistor to send the signal to the error amp of the ps ic, if it has one, for a circuit. less practical, but simplest, is to run the outputs through a transformer. transformers only transfer ac.
 
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