![Loudspeaker Protection](http://electronics-diy.com/schematics/452/protect-final.jpg)
Something you should use in any amplifier, especially in discrete
amplifiers, is loudspeaker protection. The first part is the DC
detector. This circuit will trigger the Off output if DC is present on
the audio lines. The input goes through a low pass filter and then
through the diodes. If there's any DC on the lines it will turn on the
two transistors who will then turn on Q3, which triggers the Off signal.
![Loudspeaker Protection](http://electronics-diy.com/schematics/452/protect-schem1.gif)
![Loudspeaker Protection](http://electronics-diy.com/schematics/452/protect-schem2.gif)
![Loudspeaker Protection](http://electronics-diy.com/schematics/452/protect-schem3.gif)
![Loudspeaker Protection](http://electronics-diy.com/schematics/452/protect-layout.gif)
![Loudspeaker Protection](http://electronics-diy.com/schematics/452/protect-pcb.jpg)
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