Hi Mr. Mile ,i don't want a simple triac protect,the only reason looking for triac protect is that i didn't like the relay contacts in signal path. I prefer some transistors and fuses blown in case of failure than a dirty contact in signal path.
I will build it. Miles i have one request. Have you you logo in 8bitsbalck and white?
Marc
thimios
There is another way to protect the amplifier.
The idea is very simple, You can monitor DC at the output and voltage drop on the emiter resistor (to minitor the current) at the output transistor and make the protect circuit to swith off the amp, for example you swith off input LTP CCS's so all the stages will be off, including output transistors.
Simple and bullet proof + no relays in circuit !!!
Regards Peter
There is another way to protect the amplifier.
The idea is very simple, You can monitor DC at the output and voltage drop on the emiter resistor (to minitor the current) at the output transistor and make the protect circuit to swith off the amp, for example you swith off input LTP CCS's so all the stages will be off, including output transistors.
Simple and bullet proof + no relays in circuit !!!
Regards Peter
I'm tired .... is too much thinking for me jejejeje 
Swith off input LTP CCS's can not swith off broken output transistors and will not protect speaker from DC.
Regards
That is truth but what if we monitor DC at the output and voltage drop at emiter resistors (current in SOA range at the output transistors) ? They should not fail.
Would be not enogh ?
If not looks like a relay is the only good option.
thx
A low RDS mosfet on each power rail would work instead of a relay. Series mosfets on the speaker output works too.
Some amplifiers turn off main transformer by triac if there is DC on amp output... optotriac MOC3040 can be use instead relay
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