amp with little sound

[Jchan]

Please help!! This is my setup: HU Alpine cda9813, 4 channels fosgate 500x amp, front comp. speakers, and subwoofer. Here is my problem. After I hooked the front rcas output from HU to channels 1& 2 and hooked up the sub.rca output from HU to channels 3 & 4. When I turned on the stereo there is very little sound to the comp speakers and low bass. I tried to adjust the gain on the amp. but it 's helpless. The power is OK to the amp. (14.4 V when car idle) I wander what 's going on and everything is hooked up correct. Your help is greatly appreciated.

[schn0354]

Make sure you have an excellent ground connection. Attach the ground lead to the vehicle frame if possible.