possible ground noise?

i am running a pioneer avic z3 in a 2008 wrx and i am getting this strange noise comming from my subs. im running a 2 channle (bridged) MTX amp to a pioneer premire sub. all the grounds seem good. when i have the gain all the way down i do not hear the noise. its not a constant humm or whine or anything like that at first. it starts off as small blurts then a pulsating noise then depending on whet gain i touch either turns off the noise or it just gets louder and blurps harder. any info on this?

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Craig S.

Is there a screw between the left and right RCA jack on the amp?  Is it or was it ever loose?   It sounds like there is a broken connection under the RCA jack.  To verify this you will need to take the amp out of the vehicle, remove the cover so you can get to the RCA jack, gently push the RCA jack towards the middle of the amp, if it moves easily it is broken.  It will be broken on the conductor nearest the edge of the board.  You can repair it by soldering a small wire from the base of the jack to the top of the board.  A computer hard drive ribbon cable wire works great.  Let me know if you need a picture.

thanks. im going to open up the amp today and see if thats my problem. i noticed when i moved the RCA's by hand at the amp the noise temporarliy went away and then when i let go it came back. ill post back after i look at the amp

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Craig S.

If you move the RCA jacks and the noise goes away, that is your problem.

i opened it up and the the conductor is broken. i dont have any soldering equipment as of right now but the (i think) grounding area of the RCA's is the one you are talking about right? the metal piece just came out and when i looked at the other RCA it didnt move at all. so its basically making that noise due to a bad grounding of the RCA's right? thanks for the help

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Craig S.

You are correct.  There is not enough room to just solder the 2 pieces back together.  You will need to get a few inches of some really small stranded wire.  An IDE ribbon cable from a hard drive, or a floppy drive, works great.  Strip both ends of the wire, tin both ends,  apply some solder to both halves of the RCA connector, then solder one end of the wire to the top and the other end to the bottom connection.  Even if you have enough room to solder the 2 pieces back together, don't do it, it will break again.