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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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What amps are you running? Maybe you are using the wrong RCA cables; depends on the amps used.
Typically alternator whine, noise from power windows is a ground issue but could be an issue wit the amps as well.

I think there was another similar thread recently started but not sure if that guy has made any headway either.
 

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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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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?
 

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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.
 
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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.
 

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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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What RCA's have you tried?

If you have a multimeter you could try measuring the AC voltage levels that your alternator is putting out. If its too high it can mean your alternator is having an issue and emitting noise. Similar to a bad spark plug wire which would be emitting ignition noise.
 

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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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I just reread your original post. It sounds like you are getting the noise from the RCA's of the HU and the amps.
You don't have the noise when using deck power.
You don't have noise using phone directly to amps.
To me this sounds like the HU unit is picking up the noise and sending it to the amp, or the noise is being picked up from the RCAs.

This may be a pain but can you temporarily use an amp up front near the HU; just for testing purposes?
 

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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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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.
 

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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.
 

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first route positive and negative wires from the same spot as you use it for all the rest components in the system. Reduce gains on amps, check if rca cables run parallel with power cables, or are they in close proximity to cars computer, fuel pump,....
 

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What RCA's have you tried?

If you have a multimeter you could try measuring the AC voltage levels that your alternator is putting out. If its too high it can mean your alternator is having an issue and emitting noise. Similar to a bad spark plug wire which would be emitting ignition noise.
this….Bad diodes in the alternator will cause noise because of a tiny AC ripple. Most car shops can test this… a multimeter won’t do you any good

Also I didn’t read it all but there is different rca types. Twisted pair is one type. I can’t remember the other. It’s too early in the morning still
 

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this….Bad diodes in the alternator will cause noise because of a tiny AC ripple. Most car shops can test this… a multimeter won’t do you any good

Also I didn’t read it all but there is different rca types. Twisted pair is one type. I can’t remember the other. It’s too early in the morning still

You can measure AC with a multimeter.

OP, what happens with the engine off? Do you still have noise?
 

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this….Bad diodes in the alternator will cause noise because of a tiny AC ripple. Most car shops can test this… a multimeter won’t do you any good

Also I didn’t read it all but there is different rca types. Twisted pair is one type. I can’t remember the other. It’s too early in the morning still

You can measure AC with a multimeter.

OP, what happens with the engine off? Do you still have noise?
 

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You can measure AC with a multimeter.

OP, what happens with the engine off? Do you still have noise?
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
 
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