Strange distortion/ noise, spent months trying to figure out why

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shadyyy

CarAudio.com Newbie
So, to begin, I'll list what I'm running for my system.

Vehicle: 2002 Subaru Impreza Wagon (this is somewhat immaterial because I'm not using any of the original sound system, door speakers, amp and all)

Head Unit: JVC KD-R520
Speaker Amp: Rockford Fosgate R250X4 Prime 4-Channel
Sub Amp: DB Drive OKUR A4 2400D
Subs: x2 Sundown Audio SA-10

I've been running this system for quite some time now in my Impreza. For the last few months I've been trying to figure out exactly what's going on within my system. Out of the blue, I started receiving this very dull tone from the subs. I could usually run the volume around 40-46 and it sounded amazing. Now, its like its been cut in half, and there is also some sort of distortion/interference coming through. This happens intermittently and sometimes will stay away for a few hours but then it happens again. The system seems to operate as normal as soon as the car is started, but eventually loses its wonderful bump. It sounds like with every note that plays, there's an extra sort of unwanted vibrating sound, or like a buzzing sound. I have sorted through all of my connections, found nothing. I replaced the RCA's, that still did nothing, checked my battery voltage and voltage drop, still nothing. I'm curious as to whether or not this could be a grounding issue? The DB Amp is grounded to the floorboard under my back seats. The paint is ground off and it does make solid connection, but is it worth my time to replace that with a full on returning negative cable to ground to the battery? I know for sure that both subs are perfectly fine, because the issue comes intermittently. I was curious as to whether it was an amp issue, but I'm not fully certain, hence why I'm here asking questions. If anybody has any input please do let me know. I really want to get this system going again!
 
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I'm curious as to whether or not this could be a grounding issue?
I was thinking this as well. If the ground point has become corroded from weather/time or loosened up that may cause you trouble or if the cable that grounds the - terminal of your battery to the frame is failing that would do the same thing.

My other suspect is the head unit. JVC is basically just last year's Kenwood with a different brand name and I've had issues in the past with noisy RCA outs from older Kenwoods. Can sometimes be band-aided by grounding out the outer part of the RCA plug to the head unit chasis but really if that internal ground fault is happening it's time to start head unit shopping.

Do try to test either your RCA outputs from the deck into a known working amp or try the 3.5mm to RCA with your phone directly into the amp to try to isolate the culprit.
 
Try connecting the sub amp to your phone with a 3.5mm to RCA patch cable and play a few songs. See if it repeats the issue. If the issue repeats, then it is from the amp onwards.
I will give this a try, I thought about trying this but I wasn’t entirely sure if I can fabricate one, but it’s probably best to just purchase one. I’ll update you after I try this!
 
I was thinking this as well. If the ground point has become corroded from weather/time or loosened up that may cause you trouble or if the cable that grounds the - terminal of your battery to the frame is failing that would do the same thing.

My other suspect is the head unit. JVC is basically just last year's Kenwood with a different brand name and I've had issues in the past with noisy RCA outs from older Kenwoods. Can sometimes be band-aided by grounding out the outer part of the RCA plug to the head unit chasis but really if that internal ground fault is happening it's time to start head unit shopping.

Do try to test either your RCA outputs from the deck into a known working amp or try the 3.5mm to RCA with your phone directly into the amp to try to isolate the culprit.
I was thinking the same, and yes I definitely agree with the JVC issues. It’s hard to let go of a deck that’s treated me so well over the years, I am not a man of change lol. But, I did forget to mention I got a clone of the deck I’m using. It was used, but I figured it was cheap and wouldn’t hurt to try and see if it resolves my issues. It didn’t. Still the same result. Unless that JVC deck was bad also which is entirely possible. So, that’s where the ground idea hit me, because of the intermittent issues I’m wondering if there’s a correlation there. Correct me if I’m wrong, but the impedance at the ground can change, like you said with corrosion or weathering on the bottom of side of where I’m grounded to? After I get off work I will attach some photos of what I got going on there. Thanks man!
 
You mentioned that it sounds fine when you first crank the car. Does the issue always go away when you turn the car off and back on?
No, not always, in fact very rarely does that work. It’s almost as if the longer my car sits, the next time it starts up everything functions properly for anywhere from a minute to two hours. If I don’t start it for a day or two, then revisit my issue, it works. Then out of the blue it suddenly stops working. I’m not sure if that info helps you in my quest any, but that’s the best I can explain it.
 
I was thinking the same, and yes I definitely agree with the JVC issues. It’s hard to let go of a deck that’s treated me so well over the years, I am not a man of change lol. But, I did forget to mention I got a clone of the deck I’m using. It was used, but I figured it was cheap and wouldn’t hurt to try and see if it resolves my issues. It didn’t. Still the same result. Unless that JVC deck was bad also which is entirely possible. So, that’s where the ground idea hit me, because of the intermittent issues I’m wondering if there’s a correlation there. Correct me if I’m wrong, but the impedance at the ground can change, like you said with corrosion or weathering on the bottom of side of where I’m grounded to? After I get off work I will attach some photos of what I got going on there. Thanks man!
Hah, the old Kenwood I'm thinking of I liked so much I had also bought a second one right after they dropped that model so that I'd have a spare when mine failed. Both did eventually go the same way.

Take the ground off and see. Corrosion could work its way in there anywhere. Again, keep in mind part of the circuit the - path is following is through the car's body/frame and through that shitty little wire up under the hood that connects the - terminal on the battery to the frame up under the hood so do check that if you're trying to diagnose possible bad ground.

You probably have ruled out your source unit at least. Do both amps give you issues or just the sub amp? Might be something failing internally in that amp. I've had some strange sounds get into amps from transformers that are not well glued from the factory that start to loosen up and unwind and I'm sure there's other stuff that could be failing. Not sure how old your amp is but my memory tells me DB Drive has made an amp by that name for over a decade now.
 
I believe so! And sounds like we are alike lol. So yeah, I’m just facing issues with the sub amp. It’s likely that my chassis ground is screwed. I’ll have to investigate that as well. There are still a lot of unknowns, but I can say the connection at the amp ground is clean, there is no corrosion. So, let’s put it into perspective this way. Im definitely facing one of these three problems, A) Amp failure B) Bad ground spot or C) bad chassis ground, I suppose it is a possibility about the HU as well. I’ll also try what the other fella said and run a 3.5mm to rca direct to the amp and try that as well. What are the chances that it could be anything else under the sun, lol?
 
I believe so! And sounds like we are alike lol. So yeah, I’m just facing issues with the sub amp. It’s likely that my chassis ground is screwed. I’ll have to investigate that as well. There are still a lot of unknowns, but I can say the connection at the amp ground is clean, there is no corrosion. So, let’s put it into perspective this way. Im definitely facing one of these three problems, A) Amp failure B) Bad ground spot or C) bad chassis ground, I suppose it is a possibility about the HU as well. I’ll also try what the other fella said and run a 3.5mm to rca direct to the amp and try that as well. What are the chances that it could be anything else under the sun, lol?
Hah, the old Kenwood I'm thinking of I liked so much I had also bought a second one right after they dropped that model so that I'd have a spare when mine failed. Both did eventually go the same way.

Take the ground off and see. Corrosion could work its way in there anywhere. Again, keep in mind part of the circuit the - path is following is through the car's body/frame and through that shitty little wire up under the hood that connects the - terminal on the battery to the frame up under the hood so do check that if you're trying to diagnose possible bad ground.

You probably have ruled out your source unit at least. Do both amps give you issues or just the sub amp? Might be something failing internally in that amp. I've had some strange sounds get into amps from transformers that are not well glued from the factory that start to loosen up and unwind and I'm sure there's other stuff that could be failing. Not sure how old your amp is but my memory tells me DB Drive has made an amp by that name for over a decade now.
Sorry, forgot to hit the reply button! But let me give these things a try and come back to it. If you have any other suggestions let me know! My reply earlier is somewhere on the thread lol.
 
this is the noise I’m talking about by the way. I just left work and on my way home the system sounded fantastic. As I pulled into the driveway it reverted to sounding like this, take a listen:
Hah, the old Kenwood I'm thinking of I liked so much I had also bought a second one right after they dropped that model so that I'd have a spare when mine failed. Both did eventually go the same way.

Take the ground off and see. Corrosion could work its way in there anywhere. Again, keep in mind part of the circuit the - path is following is through the car's body/frame and through that shitty little wire up under the hood that connects the - terminal on the battery to the frame up under the hood so do check that if you're trying to diagnose possible bad ground.

You probably have ruled out your source unit at least. Do both amps give you issues or just the sub amp? Might be something failing internally in that amp. I've had some strange sounds get into amps from transformers that are not well glued from the factory that start to loosen up and unwind and I'm sure there's other stuff that could be failing. Not sure how old your amp is but my memory tells me DB Drive has made an amp by that name for over a decade now.
Seems as though I may have found some water damage after pulling the amp apart? At least it seems like moisture got in there.
 

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What are the chances that it could be anything else under the sun, lol?
You're certainly ruling stuff out here. I'd say if the ground from amp to chasis is sound and you're not experiencing trouble with the other amp nor any other of the car's accessories/electrical there's not much left besides the sub amp and perhaps signal cable running to that.
 
may have found some water damage after pulling the amp apart?
That may be just some residue from something done during manufacturing. While it's open you might see if any of the larger components feel loose or appear broken at the land, otherwise there's not much that's really user serviceable for a layman in there.
 
That may be just some residue from something done during manufacturing. While it's open you might see if any of the larger components feel loose or appear broken at the land, otherwise there's not much that's really user serviceable for a layman in there.
Maybe so, I'm certainly no technician. I did read that, it does not hurt to clean it up a little bit with Q-tips and isopropyl alcohol, very lightly. I went ahead and cleaned it, there was certainly some corrosion on some of the components inside the amp. Not banking on that, but, I figured it wouldn't hurt. Now, as far as that signal cable, what would cause that to create the noises I'm hearing? I'm asking out of curiosity of course. The signal wire is spliced to reach the amp, because at one time it got pulled out, and was too short to go back into its rightful position. I'm running an 18 ga wire as a jumper from the speaker amp to the sub amp. It does show 14.xx volts but, I'm wondering now if that splice isn't creating issues?
 
Maybe so, I'm certainly no technician. I did read that, it does not hurt to clean it up a little bit with Q-tips and isopropyl alcohol, very lightly. I went ahead and cleaned it, there was certainly some corrosion on some of the components inside the amp. Not banking on that, but, I figured it wouldn't hurt. Now, as far as that signal cable, what would cause that to create the noises I'm hearing? I'm asking out of curiosity of course. The signal wire is spliced to reach the amp, because at one time it got pulled out, and was too short to go back into its rightful position. I'm running an 18 ga wire as a jumper from the speaker amp to the sub amp. It does show 14.xx volts but, I'm wondering now if that splice isn't creating issues?
So, to follow up, I got everything working properly again. If you refer to the photos I sent of the amp internals, you can see there is that white residue. What I didn’t get the chance to get a photo of was the bottom side of the board, which had some mild corrosion as well. I cleaned the board very carefully with q-tips and isopropyl alcohol, and every single contact. This was a two hour process, but once I finished up, I allowed everything to completely evaporate overnight. Put everything back together, and boom, it’s operating normally again. I hope this helps anyone facing a similar problem as me, but do it at your own risk. If done improperly, you can permanently damage a board that may not even have issues. Thank you guys for the help!
 
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shadyyy

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