So have the amp and sub installed and nothings coming out of the sub? I have power to amp,the lights are on, its a mono system, I've double and triple checked the wiring and its correct,have the remote gain lit at the dash,I've tried 2 head units,same,I hooked up another speaker to amp to rule out bad sub,nothing,the HU is set correctly to sub mode, only thing I can think of is no low level outputs from HU or amp isn't putting out,fuses are good all around,everything is new except the Head units,both power the rest of speakers just fine,have my son helping and he's scratching his head to! how can I test the HU sub output? any Ideas? see anything in these pic's?