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amp problems feedback coming through sub

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Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
Printed Date: January 20, 2022 at 4:49 AM

Topic: amp problems feedback coming through sub

Posted By: beefey
Subject: amp problems feedback coming through sub
Date Posted: January 19, 2008 at 7:36 PM

I just changed out the shock mounts in my 98' 3-series bimmer so I had to take out my amp and when I put it back together this is what I am dealing with...

My Equipment:

1. Audiobahn 840w RMS amp (sorry not sure of exact model #)

2. Alpine 10" Type R' Sub wired in parallel

Everything worked fine when I took it out now when I put it back in these are my symptoms, I get a constant base tone from the sub something like a feedback sound from a microphone but constant low tone... even with the stereo deck off it does this.  When the deck is on you dont get any music through the subwoofer.So does this mean:

1. My amp is shot

2. RCA cables have interferance coming through them (they are bad)

3.  Sub is shot.


Posted By: i am an idiot
Date Posted: January 19, 2008 at 7:46 PM

Pioneer radio????

Posted By: Alpine Guy
Date Posted: January 19, 2008 at 10:49 PM
Possible loose ground under the hood, or at amp. And possible Pioneer RCA issue like stated above.

2003 Chevy Avalanche,Eclipse CD7000,Morel Elate 5,Adire Extremis,Alpine PDX-4.150, 15" TC-3000, 2 Alpine PDX-1.1000, 470Amp HO Alt.

Posted By: dukill
Date Posted: January 21, 2008 at 1:55 PM

I am having problems with my subs also.   They start to distort / pulse in and out very hard and very slow whenever I turn up the volume on the headunit.  The reason I posted was because I am running a Pioneer Avic D3 and I was wondering what the problem with the RCA is that you are refering to.  I have replaced the RCAs and I think I have a pretty good ground at the Amp.  I also tried a different amp and it did the same thing.  It couldnt have anything to do with the remote wire would it? I am running the D3 with a MTX 4250D amp and 2 MTX 8000s 10"s.  Thank you for your time.  I dont mean to hijack the thread I guess i was wondering if you could tell me what the issue is with pioneer RCA outputs.

Posted By: i am an idiot
Date Posted: January 21, 2008 at 5:49 PM

Try taking a length of small wire, strip both ends of it.  Ground one end, and touch the other end to the shield of the RCA cable that goes to the amp in question.  If this makes a pop and then the amp starts acting properly, then yes this is your problem.  It is not an easy internal fix on the D3.  This is just as effective and easy to do.   The other end of the wire in this picture needs to be grounded.  This needs to be done behind the radio, not at the amp.    Picture won't upload at the moment  I am going find a thread with the pic in it.

Posted By: stuntinonabusa
Date Posted: January 22, 2008 at 2:07 AM
definitely sounds like bad rca inputs at the amp or outputs at the head unit...   my guess would be the amp....

if at first u dont succeed........ lower ur standards

Posted By: dukill
Date Posted: January 25, 2008 at 8:54 PM

Thank you guys.  I followed the directions and picture sent to me by i am idiot and everything is working perfectly.  My solder job was not as nice as the picture but it is solid and works.  Is this common on pioneer radios?  I love my D3 I now only have 3 complaints the rca deal, ipod interface, and I can barley get it in my truck dash because there is so many damn wires but just minor compliants.  Do you guys usually solder your wiring harness connections?  Thank you agian you saved me hours of trouble shooting and cusing.

Posted By: i am an idiot
Date Posted: January 25, 2008 at 9:28 PM

Glad to help   Let's see if the picture will upload today.  Just in case somebody else stumbles across this. 


Posted By: tedmond
Date Posted: January 26, 2008 at 6:35 AM
looks like a cold solder joint =D but i have tried that befor and it sure does work. why does this only happen with pioneer? i assume they would fix the problem in their newer decks but just recently installed a 4900IB and still got noise.  

Posted By: dukill
Date Posted: January 26, 2008 at 9:08 AM
What do you mean cold solder?

Posted By: i am an idiot
Date Posted: January 26, 2008 at 9:38 AM

He was talking about the solder joint on my picture.  No need for you to panic Dukill

Posted By: beefey
Date Posted: January 28, 2008 at 11:25 AM

Problem solved... new audiobahn amp is fried. I had it tested at best buy and same doodie. Audiobahn wont take the hit so it looks like I will damn... Thanks guys for the input.


Posted By: DYohn
Date Posted: January 28, 2008 at 11:32 AM
Friends don't let friends buy Audiobahn.  posted_image


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