I just got done installing my Alpine cda-7875 HU, and there seems to be a problem with the bass. It's on ALL the time, real low and mellow like...and it doesn't change, no matter how high/low you set the bass. I checked all my wiring, and it seems to be correct. It's got 4V pre-amp output for the subs. The amp is a fosgate 250a2. I was using it before with my stock HU and some of those PAC controllers, and everything worked fine. Now, I am using RCA's straight out of the HU back to the amp. Everything for the amp is hooked up correctly. Any ideas what the hell could be going on? Once again, even when the volume is at 0 on the HU, there is a very low mellow hmmmmmm coming from the sub.
HELP!!!
Everything else works fine, incl. head unit, and all door,rear speakers.

 

Does it change at all as volume or engine speed changes?

Sounds like line noise of some sort. Your power wire and RCA wires are run on different sides of the car, right? Most noise in car audio is typically alternator whine, not droning interference, so I dunno for sure what to say. Something else electronic might be operating in the low frequency range similar to if you hook up a home stereo to a computer, in some systems there's droning bass through say, a home sub. This happened to me and an in-line attentuator alleviated the noise.

 

Yes, power wire and RCA's are run on seperate sides. I have had this amp/sub combo hooked up for about 6 months, but I was using the PAC controllers tapped into the rear speaker wires. And no, I am getting no bass at all from any songs from the sub. I am thinking about hooking up the RCA's to the REAR RCA's coming from the HU, just to see if maybe the SUB outs are bad...When the radio is ON and I connected the RCA's going to the amp to the RCA's from the HU, they make a popping sound, then once they are connected, the low whine.
Thanks,
Rob