Hmm...is there any particular procedure for hooking up the cable? The manual says to push the green button on the front panel to the on position and then attach the cable. It does not, however, specify if the main power button should be on or off or if the reciever should be on or off. I am guessing that they should both be off but this does not work and I am hesitant to make the connection while the units are powered up. I have already enabled the 12v trigger from the setup menu on the 56txi but when I plug in the cable I get sound only from the sub even though the 770 is on. The sub is the only thing running from the pio's amps, everything else is running through the 770. If I unplug the cable I get sound from all channels. Any suggestions?