You can set the JC1s up so that they have a staggered turn on cycle. You do this by adjusting the turn on delay control at the back of the amp. Even if they get simultaneous 12 V turn on signals, they will power up after different delays. You should not need staggered 12 V turn on signals. I do this with my JC2 powering up both my JC1s. Same 12V siganl from the preamp, but I have the delay set differently on each JC1.
I am not sure what using the 12V turn on signal would have to do with DC coming from the pre-amp. They are completely different issues. DC on the audio input to the amp triggers a fault condition which puts the amp in a protection mode. Unless the implication is that the JC1s are powering up before the DC levels on the preamp settle to zero. In that case use the longer delay settings on the JC1.
I am not sure what using the 12V turn on signal would have to do with DC coming from the pre-amp. They are completely different issues. DC on the audio input to the amp triggers a fault condition which puts the amp in a protection mode. Unless the implication is that the JC1s are powering up before the DC levels on the preamp settle to zero. In that case use the longer delay settings on the JC1.