Noise Coming Through Subs

Robin0925

Junior Member
Hey everyone I'm having a problem with my amp.

Bought a 2010 Altima, and put my subs with a new Alpine deck in it. Everything was working fine for several months. Then I unhooked it, installed some 6x9s in the rear, I did move the amp wires around a bit, and when I hooked the amp back up I was hearing engine noise coming through the subs.

I also can hear noise from a CD spinning in the deck, when I have the source set to CD. It thumps quite loudly when I first turn on the deck as well. I installed my old deck, all the same issues. So I'm pretty sure it's not the deck itself. I have my ground wire connected to a pre-existing bolt in the trunk. I sanded away the paint to get a good connection, and it was working fine prior to installing the 6x9s. I know that's not ideal, but it has always worked for me in my other cars, and did in this new car until now.

I also tried a different RCA cable, which I strung through the car over the seats so it did not touch any metal or anything. Same problem. Something that really baffles me, is if I push on the RCA cable at the amplifier just right, the noise disappears. As soon as I let go the noise comes back. Its an older mono amp, around 10 years. Rockford Fosgate 500bd.

So, it seems like it's probably a grounding issue, but I really don't know what to do next. I would love any ideas on how I can diagnose this problem. I'd rather not pay a shop. Thanks in advance for any insight!

 
you may have an issue with the RCA ground on the amplifier, when you push on it, it's pushing contact against the ground eliminating the noise. pull the amp apart and check the ground connection, it doesnt make sense why you'd get engine noise after putting new speakers in unless you actually touched the ground

 
Yeah, I'm assuming installing the speakers was coincidence, or I did something I don't realize to jack up the ground connection somewhere.

I took the amp apart, but honestly I don't know what to look for. I can't see anything thats not connected right at the RCA input.

Today I tried to ground the amp elsewhere, under the back seat to a bolt holding the seat in place. It actually would work after I jiggled it sometimes. So, I'm thinking maybe I just need to find a really good spot to ground it. Probably will have to drill it myself I'm guessing. Which, I'd rather not but if that's what it takes. I just wish I knew a way to test it, so that I'm sure what the problem is.

 
If you have some extra wire lying around,or buy some from Wally world just to run to another location for a new grounding spot to test would work..prob cost you like $20 bucks or less for some wire that you could prob use in the future,or resale to a friend

 
Yeah, I'm assuming installing the speakers was coincidence, or I did something I don't realize to jack up the ground connection somewhere.
I took the amp apart, but honestly I don't know what to look for. I can't see anything thats not connected right at the RCA input.

Today I tried to ground the amp elsewhere, under the back seat to a bolt holding the seat in place. It actually would work after I jiggled it sometimes. So, I'm thinking maybe I just need to find a really good spot to ground it. Probably will have to drill it myself I'm guessing. Which, I'd rather not but if that's what it takes. I just wish I knew a way to test it, so that I'm sure what the problem is.
You can use that bolt if it is exposed underneath the vehicle,enough to get a nut/and maybe a washer on it to attatch another terminal with a new ground wire to be added to the frame underneath the vehicle without having to drill a hole in the car..Clean that area real good from paint and coating,and place a washer ,old amp ground and bolt it back down, and run new ground wire with exposed bolt underneath to frame/cleaned off.Basicly your are just extending the ground wire,and not having to drill a new hole in the floor pan/ect.Ive done this on a couple of vehicles in the past, and works very well..Just as you are running a ground wire to the frame for a solid ground location

 
You can use that bolt if it is exposed underneath the vehicle,enough to get a nut/and maybe a washer on it to attatch another terminal with a new ground wire to be added to the frame underneath the vehicle without having to drill a hole in the car..Clean that area real good from paint and coating,and place a washer ,old amp ground and bolt it back down, and run new ground wire with exposed bolt underneath to frame/cleaned off.Basicly your are just extending the ground wire,and not having to drill a new hole in the floor pan/ect.Ive done this on a couple of vehicles in the past, and works very well..Just as you are running a ground wire to the frame for a solid ground location
You will prob need only about 3 foot of ground wire to do this.If its not long enough..you can get a longer bolt from Orileys for about $3 bucks, and prob spend another $2-10 bucks on washers and nuts,and another pair of terminals? Maybe spend a total of $20 bucks?

 
Well I'm still completely baffled. I did some more testing today, and nothing seems to be working as far as grounding the amp. I'm wondering if it's not a ground loop, maybe? I'm not an expert by any means, but since I can hear the CD spinning through the subs, doesn't that mean the noise is getting into the system somewhere up front at the deck? I have no idea what to do.

 
Use a different headunit or aux to rcas. Just keep in mind when using aux to rcas if you have backfeed it won't show up because you only do one rca at a time and your phone isn't grounded to the vehicle

 
I've tried using my old deck, same issue. I'm starting to think my issue lies within the amp, as mitchell0715 said up in reply #3 . I've taken apart the amp, and the soldering of the RCA input looks like it may no longer be solidly connected to the circuit board. It's hard to tell for sure though, since it's so small. But I'm really feeling like this is the issue. Nothing else makes sense to me.

 
I've tried using my old deck, same issue. I'm starting to think my issue lies within the amp, as mitchell0715 said up in reply #3 . I've taken apart the amp, and the soldering of the RCA input looks like it may no longer be solidly connected to the circuit board. It's hard to tell for sure though, since it's so small. But I'm really feeling like this is the issue. Nothing else makes sense to me.
can you get us a picture of the connection?

 
Here is the closest I could get. Left to right goes Input White, Pass Thru White, Input Red, Pass Thru Red. I feel like both Inputs look like there is a gap in the soldering.

 
Well I went ahead and tried to solder the connections. Either I didn't do it very well, or that wasn't the problem because the noise is still there. I just wish I knew if it was the amp, or the wiring, but I don't have a second amp to install and find out.

I feel like I've tried everything and have gotten no where.

Is it possible that it could be something with the wiring harness to the deck, or the antenna adapter?

 
Here is the closest I could get. Left to right goes Input White, Pass Thru White, Input Red, Pass Thru Red. I feel like both Inputs look like there is a gap in the soldering.
Those solder connections don't look very good, but it looks like those are the center pin only. where are the shields grounded? that is your likely culprit. you can try touching a wire to the amp chassis and the other end to the RCA shield to re-create the connection.

anytime you have an open signal ground you have an opportunity for noise. this can happen at the head unit, amp, or inside the RCA wiring.

 
Those solder connections don't look very good, but it looks like those are the center pin only. where are the shields grounded? that is your likely culprit. you can try touching a wire to the amp chassis and the other end to the RCA shield to re-create the connection.
anytime you have an open signal ground you have an opportunity for noise. this can happen at the head unit, amp, or inside the RCA wiring.
More fiddling with it today and I'm sure it's something to do with the amp. RCAs unhooked from the amp, and when I was messing with the punch bass remote, I was getting a little bit of noise through the subs, you could feel them moving.

I'm debating just getting something new. Even though I love this amp and it's a perfect match for my subs, it is 11 years old.

When you say where are the RCAs grounded, I'm honestly not sure what to look for. I can hook up amps, but I'm not real familiar with the inside components. It looks to me like the RCA block has 6 pins going through the circuit board on the bottom side. 2 input, 2 pass thru, 2 that I can't really tell what they are connected to, something in the middle of the block I would guess?

 
the shield is the outer metal. you can use a DMM to measure resistance between the amp rca jack shields and the amp chassis. older amps can be more sensitive to grounding issues (though 11 years isn't that old). i like the RF bd series as well, a great amp. try some shield grounding before you replace the amp.

 
Just got back from a friends house, where I installed my amp in his car. Same problems occur. So, it's definitely the amp. And I'm definitely feeling like it's the RCA input block. The red and white plastic parts are loose on the input side, and wiggle around inside of the metal shielding. I must have yanked on them or something when I was unhooking the amp.

Would this be an easy repair? What might it cost at a shop? I'm going to call a shop tomorrow and ask. But, I'd love some input on how easy or hard this might be. I looked around for an RCA block, but I couldn't find one to purchase that looked like what is in my amp. At least I know what's going on now, for sure.

 
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Robin0925

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