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Discussion Starter · #41 ·
Damn it, called it too early. New amp did not solve it, same issue...
This is killing me lol.
I tried again connecting the headunit by the amp, seemed to work OK.
I called a professional audio installer, who came over and tried troubleshooting different solutions.
Basically I refused to understand why I had no whine if I powered the headunit directly from the amp and grounded it directly on the amp.
He poked around and tried different grounds, and did not have anymore success than me.
Only way to reduce or eliminate the whine was to power the headunit, and especially ground it on the amp.
Grounding HU on the amp seemed to effect the biggest change. Using power from the amp appeared to make it even better, but I couldn't tell 100% if that's the case or if I'm hallucinating at this point.
Also when testing the new amp, only using one channel, I.e. channel A or channel B, the noise would go away.
With both channels connected, however, the noise would come back.
So the tech suggested the amp might be the issue.
When I was testing things out before with my friend, who helped me install the system, he would pull out rca cable and plug them back and forth with the car running.
The tech said that doing that could've shorted the amp.
Anyways, it was decided that nothing better can be done than just running a positive and negative from the amp to the headunit to eliminate the problem.
So today I spent all day taking the car apart to run the wires under the carpet.
I thought ok, what a backwards way, but whatever, at least I can listen to music without whine and I don't have to install the headunit by the amp, a ghetto way!
Well, after all the work was done and I connected everything, the whine is ever so strong and present!
I feel so defeated and this ground loop has sent me into a never ending loop myself lol....
I don’t know if I need to buy a third amp now or try connecting the headunit by the amp again to see what happens.

I don't understand where this damn noise comes from....the tech explained to me that it's the alternator grounding itself on the chassis, basically sending excess positive power onto the ground of the car.

I'm ready to do anything at this point to be able to get this whine fixed and finish this project.

I was watching a video


It suggested installing an alternator filter.

I'm not sure if it can help?
Normally I wouldn't care to try, but at a price of $450 I thought I'd double check with you guys..

NewMar 150-a 150 Amp Noise Filter NewMar 150-a 150 Amp Noise Filter : Amazon.ca: Electronics
 

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That price is insane, I would not buy that.

Did you rule out the head unit as the issue?
Did you try to grounding the body of the head unit?
Did you try swapping the amplifier?
Did you separate the rca from the power cable, or do cross runs.

If not try those step before going the route of an overly expensive isolator.
Post picks of your install and wire runs. That would give an idea of how things are installed.
 

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Discussion Starter · #43 ·
Yes the price is high, but it looks like a high quality device. I found a cheaper price on ebay. It's 200 usd, plus shipping, taxes, import duties etc. still comes out to over $300 Canadian, but if it has a chance of solving the issue, I don't care at this point...

Yes I tried grounding everywhere in the car, on the negative of the battery in the trunk, on the ground factory stud in the trunk, on the negative under the hood, different grounding points under the hood, drilling a screw hole in the cage under the dash etc.
Tried two headunits. Two amps.
Tried grounding rcas on the headunit, tried grounding the body of the headunit.
I think I'm going in circles now.

At this point I don't care. I'd gladly buy the alternator noise isolator, new alternator from bmw, anything to solve this as the time I've wasted is worth thousands of dollars by now and I'm no further ahead...

I just want to understand where this issue originates and to apply the strongest possible solution to this.
 

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I hear you these things can be frustrating at time, but I assure you that isolator is a bandaid. If your at your wits end, nothing I or anyone can change your mind but I would still like to try. When having a difficult problem the best way to solve it is by process of elimination and break the problem into manageable chunks. You said connect the head unit to that amp ground eliminated the problem at first. That tells me this can be solve. Solving this will require time not necessarily money. Start under the hood clean all ground connections and add a second ground to each. Reroute wire keeping power wire away from rca, make sure rca are twisted and shielded. I know it's frustrating but you can solve this. Pics of your installation may help with ways to solves this. None of us know what your installation looks like and if things are not install well it wouldn't matter how many amp head unit or ground points you use the issue may not go away. See #2 of this thread.
 

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If you havent tried a used alternator from a you pull it that might be a thought. If there is a problem with the alternator creating noise then that would be a better/cheaper solution to try than putting in a filtering device. I typically put a larger cable on the case of the alternator. I don't know if you were checking the actual quality of ground points using a multimeter or not, but that is something which could be helpful and give you objective data on how good the ground is.

It seems really odd that you can connect some rcas and get no noise while when you connect more of them the noise presents. A lot of amps can utilize just 2 channels of input and if you are using the freq filters on the amplifier then I would go that route.
 

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Discussion Starter · #48 ·
If you havent tried a used alternator from a you pull it that might be a thought. If there is a problem with the alternator creating noise then that would be a better/cheaper solution to try than putting in a filtering device. I typically put a larger cable on the case of the alternator. I don't know if you were checking the actual quality of ground points using a multimeter or not, but that is something which could be helpful and give you objective data on how good the ground is.

It seems really odd that you can connect some rcas and get no noise while when you connect more of them the noise presents. A lot of amps can utilize just 2 channels of input and if you are using the freq filters on the amplifier then I would go that route.
I heard that all alternators can cause this. Getting a scrap yard alternator would probably make my life more complicated, since I wouldn't even know if it's good or has a problem causing interference as well.
If I'm gonna replace an alternator, then I'll put a brand new one oem, that way at least I know it's a good part. It's also an expensive part so I wanted to see if I can tell, before replacing it, if it's even going to fix it.

I have a multimeter and can check for grounds anywhere. Everything I checked so far, I don't see a problem with grounds. Unless I'm not checking it right.

I'm back at it again.
Right now headunit is located in the front, grounded by a wire directly to the amp.
Constant power comes from the amp positive side, ignition wire is powered from ignition switch.

The whine is present right now with both channels, together or individually.
My amp is obviously 4 channel.

If I have two RCAs connected, the whine is there. If I have four RCAs connected, the whine is there.
If I disconnect all RCAs from the amp, there's no whine. During this time the amp for the sub is connected.

This tells me the problem is not with RCA cables. If they were picking up power noise, whine would be there even with RCAs disconnected from the amp. Also I run my RCA cables from amp to headunit in the middle of the floor, whereas the power wires run on the side of the car.
 

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Discussion Starter · #49 ·
If I then disconnect the RCA cables on the headunit, for both channels A and B or one of them, the whine is still there.
Let's say I have two RCAs connected to channel A and two RCAs disconnected on channel B. The whine gets worse if the RCAs on channel B come closer together or closer to the headunit. If I move the disconnected RCAs away from the headunit, whine gets a little bit better. But it's still present.
 

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Discussion Starter · #51 ·
I completely disconnected the headunit from the system and disconnected all RCAs from the amp.
Then I plugged one set of RCA cables in channel A. Nothing connected to them on the other end. Then I switch to channel B.
In both situations, I have the stubborn whine.
If I pinch the middle of the rca connector with my fingers, the whine get a lot worse.

So does this mean the whine is coming from the amp?

Can I narrow it down at all? Is it bad amp or bad ground? I'm going to add pictures of the install.
 

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So you figured out that the noise goes away when you power/ground everything at thr same location, the noise goes away? Congratulations, you just figured out what a ground loop is. You should ALWAYS be powering/grounding everything in the audio system at the same location for this very reason.
 

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Discussion Starter · #53 ·
So you figured out that the noise goes away when you power/ground everything at thr same location, the noise goes away? Congratulations, you just figured out what a ground loop is. You should ALWAYS be powering/grounding everything in the audio system at the same location for this very reason.
Well, this was the case before, when I moved the headunit to the trunk of the car, where the battery is located on my bmw.
Now I ran the power and ground wire from the amp to the headunit, and the noise is back.
So I'm back at square 1.
I would love to learn what's going on and how to fix it...
 

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Set your multimeter to 0.00 or .000 VAC and measure between your alternator positive and battery negative. If you have too much AC voltage then your alternator has an issue.

My '99 Dodge 3500 had this issue and the AC voltage was measurable with a $20 multimeter, something around 0.1 or 0.2 VAC and was almost zero after a new alternator. It caused the transmission to go in and out of overdrive.
 

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Discussion Starter · #55 · (Edited)
Picture 1, it's the big 0 gauge copper positive wire powering the amps. I power it directly from the battery.
The two small wires that you see on positive and negative is just for a battery maintainer.

Picture 2 is the same wire going up and a fuse.

Picture 3 is the same blue power wire going into the cutout in the trunk cover.

Picture 4 is the ground stud. Cleaned well to shiny metal. Two ground wires connected to it.


Picture 5 shows where both ground wires go. Thicker black wire goes to ground both amps.
The gold looking ground cable goes into a disconnecter box I installed just in case I need to disconnect the battery without removing battery clamps.
So the negative cable from the battery goes to the disconnect box. And then the gold ground wire goes to ground in the trunk from the disconnect box.

On picture 6 you see the disconnect box. You also see positive 0 gauge wire splitting into 2, to power the amps.
You also see the negative 0 gauge wire splitting into 2 ground for both amps.

Picture 7 shows the power wire splitting.

Picture 8 you see the capacitor.
One positive wire goes to power the capacitor and the other positive to power the amp for the sub.
In the same fashion the negative wire splits into two, where one wire goes to ground sub amp and the other negative goes to the capacitor.
Then from the capacitor, power and ground goes to the main amp for the speakers.

You will also see a double strand wire on the positive stud of the capacitor. This one goes to power the headunit.

Still on picture 8, on the most left side on the amp, where the negative wire from the capacitor goes, you see a smaller gauge wire coming out. That's the wire that goes to the ground for the headunit.

Picture 9 is just the sub amp and shows a bit more of the installation.

Pictures 10, 11, 12 just shows some more angles of the install in the rear of the vehicle.
Automotive tire Motor vehicle Hood Trunk Electrical wiring

Motor vehicle Automotive tire Hood Automotive design Bumper
 

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Discussion Starter · #57 ·
Set your multimeter to 0.00 or .000 VAC and measure between your alternator positive and battery negative. If you have too much AC voltage then your alternator has an issue.

My '99 Dodge 3500 had this issue and the AC voltage was measurable with a $20 multimeter, something around 0.1 or 0.2 VAC and was almost zero after a new alternator. It caused the transmission to go in and out of overdrive.
My alternator has a plastic cap on the positive stud so I have to put in there an extra wire and then measure positive from that wire.
As a negative at first I used alternator body and then tried different grounds under the hood.
So when I started the car, the reading started at around 0.128v and within minute dropped for 0.075v.

I disconnected the negative probe from the body of the alternator and then the AC reading stayed about the same, between 0.060 and 0.070V even with the negative disconnected.

As soon as i connected the negative people to grounds under the hood, it jumped to 0.151V.

Then I reached inside the vehicle and connected negative probe to the ground wire that I ran from amp ground to headunit ground. It was showing around 0.130V.
I couldn't reach the battery negative right on the battery.

Then just in case I used a spare 0 gauge copper wire and ran it from the battery negative to the front of the car, where I could reach the negative terminal of the multimeter.
It measured 0.130V
 

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Now things are making sense. First the wired need to be organized. Power wire need to separate from the rca. From the look of the picture it seems like the ground wire is bolted on top of sound deadener. If so remove it sand the area to be grounded to bare metal. Your install need work. Fix the install you will fix your noise issue. Take your time to ensure it's done right.
 

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Sounds like
Now things are making sense. First the wired need to be organized. Power wire need to separate from the rca. From the look of the picture it seems like the ground wire is bolted on top of sound deadener. If so remove it sand the area to be grounded to bare metal. Your install need work. Fix the install you will fix the ground loop.
^Agreed.

OP what ground bolt even is that? Appears to have yellow paint.

Also the AC voltage does appear to be high. Did you say you have noise with the motor off?
 
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