This is a simple circuit that can protect your expensive speakers from annoying "pop" sound that you hear when you turn on your audio amplifier it will provide this protections time delay about 3 to 4 seconds, DC detect in case the amplifier fails it will automatically will shut off the speaker from you audio amplifier and lastly thermal protection. The original schematic use a resistor combination with a zener diode as supply media and what I did is kept that option and add a voltage regulator as a better and easiest way to supply voltage to the circuit. To make it a lot easier on you just use the voltage regulator and not the resistor/ zener combination, install D11,6,2,1 do not install ZD2 and do not install D3. The LED can be any color you like I like green the LED will give you a status of the circuit by blinking a steady blinking is normal operation and if there is a DC detect it will turn off the speaker and begin blinking see the video this is the first prototype and works really well the BOM is update recently with new values of resistors. The AC input is from 12V to 27V AC you will need a separate small transformer or a secondaries winding from your toroidal transformer to feed the speaker protection please give a like this design I spend many weeks making the layout I hope you guys like it :) one more thing the thermal switch you connect them in series one to the left channel and the other to the right channel of the amplifier relays are 12V DC see BOM for more information.

The Automatic speaker protection gerbers files are the new version updated to PCB version 1.3 and resistor and caps values updated don't mind about the second video all values are been updated.

first video

second video