Hi
i have the fosgate 4125 and it is bidge-able it shows the diagram on the back to bridge it,so all amps dont have to have a switch to make it bridge-able,if it dont have a switch or a diagram telling you how to bridge it,than i would say it is not bridge-able
but if it is bridge-able like me mine is and i used 1 of the bridged channels to run my mtx center speaker in briged mode i run the positive with the positive and negitive to the negitive of 1 of the speakers and it seems to work fine
i have the fosgate 4125 and it is bidge-able it shows the diagram on the back to bridge it,so all amps dont have to have a switch to make it bridge-able,if it dont have a switch or a diagram telling you how to bridge it,than i would say it is not bridge-able
but if it is bridge-able like me mine is and i used 1 of the bridged channels to run my mtx center speaker in briged mode i run the positive with the positive and negitive to the negitive of 1 of the speakers and it seems to work fine