I've got a so-called stock "Premium Sound System". I added an aftermarket subwoofer and amplifier three years ago. Just today I noticed bass bleelding over from what I thought was another song. I turned the stereo off and I can still hear bass coming from the subwoofer!
I know this is probably electrical in nature but checking all the connections, I couldn't find the source of this problem. Any ideas?

 

is it a sound or just a sound almost like a wine???

 

If it sounds like just one bass note that never ends and or lasts along time, I would check the high to low level adaptor used to tie your amplifier into your system. Most good adaptors have level adjustments on them, but the level adjustments could just be set a little to high.

 

i think you need to be a little bit more specific about what kind of sound is coming from your subs.

it could be a bad RCA connection (which means you should check the RCA wires that plug into your amp),

it could be engine whine... which means you'd have to get some plastic wire covering for the exposed power wire in your engine bay. (that's just a couple of dollars at radio shack but it's a pain to put on sometimes)

is your amp connected to a stock head unit? there could be some kind of bad connection wherever wires may have been spliced to allow for that kind of connection.

 

When you added the a/mkt amp did you connect with RCA plugs or speaker cable? If you connected w/RCA then you may want to check the type of cable used - try replacing it with a higher quality cable (NOT from Radio Shack). If you connected w/speaker cable try going to RCA (if possible) - you may be picking up another radio station through your cables (this can happen if cables are not shielded).

When you turn off the head unit does you a/mkt amp stay on? If this is the case, you may want to check the connections between your amp and head unit. If it does not stay on, your rig may be haunted!!!

 

I think you are on to something. The only way to get sound through the subs after the head is shut off is if the amp is staying on. Make sure the remote turn on lead from the amp is not wired to constant 12v or even switched 12v. There should be a lead off of the head that sends 12v to the amp (small wire) when the head is powered up.