Amp/sub help

[bcmaxx]

I have an older rockford fosgate 400 w amp and matching 12" sub, and recently It started giving a lot of background noise, even with the volume turned low or off. Just a steady rumbling noise. It comes and goes works great half the time and still works just not half as good when it has this "interference" . I replaced the ground wire and relocated it to the rear seat mount, and replaced the rca wires to the deck and it seemed good for a few days. Any ideas?

 

[xcalibur223]

Are the RCA wires run next to the power wires or on opposite sides? If they're run next to each other could cause some noise.

 

[bcmaxx]

opposite they come together near the amp though

 

[xcalibur223]

hmm that's a given. Is it the sub making noise or maybe alternator whine? I can't think of much besides rechecking all the terminals and the grounds.

 

[bcmaxx]

just a low rumble , reckecked all power,ground, remote wire, rca's. Prob something inside the amp loose. Just sucks, when it works it works awesome!!

 

[xcalibur223]

It doesn't vary with engine RPM does it? Doesn't sound like it but doesn't hurt to ask. Try grounding it to another spot and if you didn't already def check the ground for the radio itself. It really sounds like a bad ground to me somewhere but this is interweb diagnostics so I could be completely wrong. You might wanna try something like a ground loop isolater which installs in line with the RCA cables or maybe a noise filter on power line running to the amp.

 

[bcmaxx]

I'll try another ground, The old ground was pretty crumby. I hate intermittent problems! When it does it again , I'll try pulling one rca off the amp at a time see if that changes anything

 

[xcalibur223]

Yea def change the ground. Some tips to maybe try to solve this: Make sure the ground wire is the same size as the power wire going in and keep the ground as short as possible so less resistance builds up. If you have time and extra wire laying around you can try to run the ground from the receiver back to where the amp is grounded to see if it is a ground loop problem from having two seperate grounds in the system.

 

[xcalibur223]

Ah I was just searching google and came across this helpful chart on crutchfields site to help in diagnosing the problem.
http://www.crutchfield.com/Learn/learningcenter/car/noise_diagnose.html

 

[bcmaxx]

thanks man, I ran a new ground wire (not just relocate the ground wire) so far so good, went and beat on the jeep in the process!!