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Discussion Starter · #1 · (Edited)
As to not waste your time with details I'll jump into the issue and what I tried so far.

Whining gets was worse when revving the engine. I understand it's called alternator whine.

Unplugging rca cables at the amp for front and rear speakers removes the whine.

Connecting my phone via Y cable to the amp eliminates the whine.

Both amps (for sub and speakers) grounded at the same chassis ground.

I tried 2 different headunits, no difference.

I tried powering one speaker directly from the headunit and not the amp - no noise.

Headunit is grounded into the metal bar under the dash.

I tried inline noise isolator filter between headunit and its power supply
No change at all
Axxess AX-ANR1000 Inline Power Noise Filter Axxess AX-ANR1000 Inline Power Noise Filter : Amazon.ca: Electronics

Tried 4 Farad power capacitor

Tried 3 rca noise isolator filters on amp side ams headunit side.

Connecting a filter just for rear or front rca cables reduces the whine. But plugging a noise isolator filter on both front and rear rca's, the noise is way worse than plugging only one filter.

I'm probably forgetting some stuff I tried.

I'm literally losing my mind over this and it's driving me crazy:)

My system is completely separate from stock audio.
One sub, 2 amps, 4 speakers and tweeters, 4 crossovers, headunit. All expensive quality components.
Power is through 0 gauge wire.

Tried grounding the amps on the battery negative instead of the body, no change. Rca cables are all high quality.

I tried powering one crossover directly from the headunit, just using wires from the pin plug, not rca.
This way there was no noise for that speaker and tweeters!

Tried grounding headunit rca female grounds directly to the headunit chassis.

I'm at a loss what could be the problem...
 

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Discussion Starter · #3 ·
Amps are
Infinity REF-704a and Kenwood KAC-9106D
Rca cables are Fospower that go from the headunit to the speaker amp.
For the sunwoofer amp, cables are Fison and have an arrow on them. Arrow is pointed in direction of the sub amp.
Headunit is Kenwood Excelon KDC-X304 although I believe I ruled out HU as an issue.
 

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Discussion Starter · #7 ·
Just a few things I can think of…. Is the ground for the amp good? Sanded, bolted to the frame or a thick area of the body, to bare metal, and sealed? Have you tried grounding your radio, amps and anything else to one location? What about using an external audio source directly into the amp? Check battery connections, factory grounds under the hood or upgrade the grounds. Last thing I can think of is maybe you’ve got a bad spark plug wire?
Yes its a bmw, so the battery is in the back.
Good clean ground. X5 2002 has a grounding point in the trunk. Can take pictures.
I didn't ground them to the same location, because the headunit is in the front and amps are in the back. But I could run headunit ground to the back. I checked ohm resistance between grounds, it's negligible.
What do you mean by a bad spark plug wire?
 

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Discussion Starter · #8 ·
OP says he tried grounding amps to negative on battery so that should eliminate the ground as a problem. I don't think the RCA cables can be considered quality, from a quick online search they seem sketchy. From all the tests, it seems like the problem stays with your RCA cables.
I tried different rca cables as well.
I tried just connecting straight across, not running them under the carpets. I.e. just connecting different rca cables from head unit to the amps. Still the same problem.
I can buy better rca cables and try that
 

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Discussion Starter · #10 ·
First try the RCA's.

If that doesn't work, try blowing up your engine, rebuilding it, and make sure to clean all the chassis grounds as you're putting the engine back in. At least that fixed the whine I had tried to isolate for a year. :oops:

Seriously though, I did find two broken chassis grounds. One mid frame at my exhaust and one in my engine bay when I pulled the motor out. No idea how the engine bay one got broken, but it was an '09 with 185k miles on it.

I cleaned up the grounding points on the engine with a wire brush. There's a wire from the engine to the chassis, all cleaned up. Other grounds under the good seem clean.
It's tricky for sure, but engine rebuild is a little too much as this point haha. I ulready overhauled everything under the hood and installed a punch of new parts.
 

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Discussion Starter · #12 ·
I can certainly test alternator amperage output. Easy step.
Not sure how to test spark plugs.

My buddy who ordered rca cables said they were good quality. The other rca cables I used were just some random cables I found when I removed previous installation from this vehicle.

I mean the subwoofer amp rca are different from speaker amp rca's. I can try them for front speakers amp. Subwoofer amp doesn't produce and problematic noise. The cables must be good?

I'm afraid that moving the amp to the headunit would be too hard. The 0 gauge power cable to the amp is not long enough.

Can I move the headunit to the amp instead?

My headunit only needs 3 wires. Power, ignition and ground.
I can ground headunit to the same bolt where amp is grounded and I can use power directly from the battery. I can just tape the red (ignition wire) and yellow (constant power) together for the time being and connect it directly to the battery terminal.

Another thing I was thinking. I have a battery charger, 2/10/75 amp. I was thinking what if I disconnect the audio system from the battery and just power it with battery charger for testing?

You say maybe the headunit picks up noise. But I do have that inline noise filter installed between yellow (constant power) wire and the headunit.
 

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Discussion Starter · #24 ·
Here is something radical. Try grounding the amp's body. If I remember right, some amps have an internal chassis ground.


Here is an Alpine BB1200 with chassis ground. I had no noise issue using it mounted on a board without an external chassis ground. If your amplifier has an internal chassis ground, try an external ground on one screw down point, and see if the noise disappears.
I think my amp body is plastic. How do I go about grounding it? Should I take off the enclosure?
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Discussion Starter · #25 ·
Yes I know this. But you need a oscope to show the ac ripple. If there is a ripple it’s a bad diode. Just measuring and seeing ac with multimeter doesn’t confirm its a bad diode. Most shops have a snapon meter that has the option to detect it
I found this information on a website online:
A multimeter can read AC voltage and can be used to test for ripple. The alternator should be replaced if AC voltage of more than 50mV is detected (in some cars as much as 100mV is acceptable).

I did mention that I have a filter installed in front of my headunit, AX-ANR1000, 35 amp filter.
Green wire on it is the input, connected to constant power wire.
Red wire on the filter is the output, goes to the headunit.
If I measure A/C at thr green wire where the filter gets its power, it reads 0.045 volts.
Then I measure on the red wire, which is the output of the filter, and feeds into headunit and provides it constant power, I get 0 volts A/C. Which tells me this filter does clean up the voltage.
The second power wire which goes to the headunit, ignition wire, does not have a filter, and it's also showing around 0.045 volts.

My headunit is only connected with 3 wires. Ground, constant power and ignition power.

For testing purposes, I connected both power and ignition wires on my headunit together and powered them through the output wire from the filter. Same noise is present.

Does this rule out bad alternator diode or should I do another test?
 

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Discussion Starter · #27 ·
Do you have any 12V tools? You could use a battery from one and power your head unit like you mentioned about the charger. Usually chargers are very noisy so might not be the best choice for 12V. Have you tried running a wire from the radio ground directly to the battery negative? If you have a grounding problem that is introducing noise at some point pull the deck so it's not touching any ground of the vehicle and get a speaker wire or any wire that is at least 16 gauge and ground it directly to the battery. You need to find out where the noise is being transmitted through. I don't believe you have a bad deck, but noise is coming from somewhere.
All my tools are dewalt 18 volts.
So I tried grounding the headunit directly on the grounding wire for the amp. See pictures. Also powered the headunit from the amp power wire.
I think it reduced the problem.
Basically if I only connect rca cables for front speakers in this set up, the whine is gone.
And when I rev rpm, no noise. As soon as I connect even one cable to the amp rear rca plug, I start getting the high pitch noise. But not as loud I believe. If I rev the engine, noise gets worse.
This is if I'm just connecting rca cable to the rear amp plug, not even connecting to the headunit. If I connect to the headunit, noise is still there as well.

Is something shorting the the amp? Rear plugs bad or smth?

I can try grounding headunit on the battery negative instead of amp negative.
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Discussion Starter · #31 ·
I keep testing.
Only rear rcas connected to the amp, no noise.
Rears and sub, no noise.
Only front rcas to the amp, no noise. Front and sub rcas to the amp, no noise.

As soon as I connect both front and rear rca cables to the amp, I get the whine.

If only front or rear rcas are connected to the amp, with or without sub, sound is crystal clear!

Does this mean something is wrong with the amp??
 

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Discussion Starter · #33 ·
Yes I tried switching the two extra rca cables, switching them between front and rear rca plugs on the amplifier. So basically both rca cables work.

But the thing is, rears and fronts work fine separately but not together.

So something happens in the amp. Either short between front and rear rca inside amp or bad grounding?
 

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Discussion Starter · #34 ·
Tried one more thing. Reversed rca cables.
Ran rca cables from front inputs on amp to rear outputs on headunits and rear inputs on amp to front outputs on headunit.
Noise is present.
If I disconnect either front or rear rca cables from the amp, noise is gone.
I'm trying to find another amp to test.
 

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Discussion Starter · #36 ·
No I didn't know it was possible.
I only had y adapter for my phone and it had 2 rca outputs, not 4.
I just grabbed another amp, lower quality, pioneer GM-A4704. It had 4 channels and it worked well with both rear and front rcas connected. Sub not connected.
So looks like it's the amp...
Gotta return this amp and order another amp.
Not sure if this infinity amp is bad on just incompatible and what to go with now.
Maybe a newer version?
 

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Discussion Starter · #38 ·
I'm very excited I figured out what's wrong! I appreciate everyone's help here as I know very little about audio and having some ideas was really nice. I've been stuck with this issue for months and finally got it resolved. Just need to figure out what amp to buy and get on with life and enjoy music:)
 

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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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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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