Universal headphone jack connection board

Audio amplifiers are used to drive the speakers but what if we need to plug in headphones ? For that purpose I have made universal headphone connection board which can be fitted to any audio amplifier. The board contains DC  protection circuit co there is no need to worry about burned headphones anymore. On PCB there is circuit breaker with normally open and normally closed contacts, that circuit breaker is used to switch off main amplifier speaker output (protection circuit or simple relay drive output). Small board but it turned out to be very handy to have it. 

--> Version V1.2 update - change in amplifier bypass circuit, do not solder R4 = 1kR resistor, please leave empty space.