I have a 4 ch amp powering the front doors speakers and one 12" sub. The rears are powered from the HU. My sub plays even when the rcas are unplugged from the 3/4 ch. on the amp. This means my 1/2 rcas are sending a signal to channels 1-4. Is it supposed to do that when there are no rcas for the 3/4 channels? The sub is bridged on channels 3/4.
The reason i ask is because the sub controls on my Alpine HU do not work. I checked all the wiring and it is correct.
So to adjust the amp i pretty much have to change the bass on the whole system. Aside from that, the sub works well.