Hi,
It sounds like there is a problem with the trigger signal being sent by your pre-amp. If the sub is turned on with no trigger connected the LED should light up in green. If you then plug the trigger cable in with no voltage on the trigger cable, the LED will turn red. Now when your pre-amp trigger signal is engaged the LED should turn green again. Please check that you have the polarity correct at your pre-amp if you have screw terminals rather than an 1/8" jack. I spoke to a customer a few weeks ago with the same problem and he had the 12V and GND connections reversed.
Andrew
