Alternator whine fix?

[red/green hawk]

I installed a JBL DSP4086. It's a 40 watts per channel 8 channel dsp/amp. The alternator whine is too much. I've tried 4 different ground points inside the cab. Should I just ground it to the battery? My power cable is running through a rubber grommet under front passenger seat and along the top of the frame and up into the engine compartment. I don't know what to do next. Noise filter? All my cable are high quality, top-of-the-line, copper. Any ideas or solutions would be appreciated.

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[j.o.y.ride]

Your RCA cables are probably too close to a strong power source. Did you run your RCA and power down different sides, or together?

 

[ShadowsPapa]

I installed a JBL DSP4086. It's a 40 watts per channel 8 channel dsp/amp. The alternator whine is too much. I've tried 4 different ground points inside the cab. Should I just ground it to the battery? My power cable is running through a rubber grommet under front passenger seat and along the top of the frame and up into the engine compartment. I don't know what to do next. Noise filter? All my cable are high quality, top-of-the-line, copper. Any ideas or solutions would be appreciated.

When I ran contests - my grounds all went out to the same place the battery negative connected to the chassis.
My power came from the same area through two 35 amp breakers.
I assume DIN cables or at least shielded cables? (twists also help)
Don't run things parallel with other wires - neat bundles look great but can cause trouble.
I didn't run RCA cables except for things I couldn't use DIN cables on. Everything was shielded.

On the other hand - I'd find it fun and interesting to put a scope on your alternator.........

 

[red/green hawk]

Your RCA cables are probably too close to a strong power source. Did you run your RCA and power down different sides, or together?

Thanks for responding. RCA cables are isolated from any power source. My amp is mounted under my glove box.

 

[red/green hawk]

When I ran contests - my grounds all went out to the same place the battery negative connected to the chassis.
My power came from the same area through two 35 amp breakers.
I assume DIN cables or at least shielded cables? (twists also help)
Don't run things parallel with other wires - neat bundles look great but can cause trouble.
I didn't run RCA cables except for things I couldn't use DIN cables on. Everything was shielded.

On the other hand - I'd find it fun and interesting to put a scope on your alternator.........

I'm gonna try running a ground to the negative battery terminal connected to the chasis. All my cables are shielded and twisted copper. When running ACC there is no extra noise only when truck is running. Should I run a noise isolator off of the amp? I have to run RCA from head unit to amp.

 

[ShadowsPapa]

I'm gonna try running a ground to the negative battery terminal connected to the chasis. All my cables are shielded and twisted copper. When running ACC there is no extra noise only when truck is running. Should I run a noise isolator off of the amp? I have to run RCA from head unit to amp.

Sounds like you've done everything right as far as good cables/quality cables, etc. One thing the guy at the sound store told me in the 80s - run all grounds to a common point to avoid ground loops.
I'd try running a ground out to the battery.......

Here's something we did with one of my components in my Comanche - to prevent whine we made a copper box and mounted the unit in the copper box and ran a ground from the box so it was grounded. That took care of a whine that sounded like a charging system whine. We assumed that because that resolved the issue, there was some RF getting into the electronics inside the case of the unit - I had CD, cassette, AM/FM whatever else there was at the time so I had a pretty complex system.

I suppose you could try noise suppression on the power side of things - but if that's happening, I wonder how clean the power out of the alternator is, what sort of ripple there is.

 

[j.o.y.ride]

I'm gonna try running a ground to the negative battery terminal connected to the chasis. All my cables are shielded and twisted copper. When running ACC there is no extra noise only when truck is running. Should I run a noise isolator off of the amp? I have to run RCA from head unit to amp.

You shouldn't need any extra components like an isolator for a simple amp install. It doesn't like something is sitting next to or something it is hooked into. It's possible your ground from glovebox area is too close to other grounds that aren't shared. It's possible your location is too noisy from factory wires. It's possible you have a bad amp or bad cables. Or are relying too much on cable shielding.

This is a trouble shooting item. Only a few real likely causes. Your 3 cable sources (+/-/RCA) aren't happy, your ground location isn't happy, or your amp location isn't ideal. Isolate 1 at a time.

 

[red/green hawk]

Sounds like you've done everything right as far as good cables/quality cables, etc. One thing the guy at the sound store told me in the 80s - run all grounds to a common point to avoid ground loops.
I'd try running a ground out to the battery.......

Here's something we did with one of my components in my Comanche - to prevent whine we made a copper box and mounted the unit in the copper box and ran a ground from the box so it was grounded. That took care of a whine that sounded like a charging system whine. We assumed that because that resolved the issue, there was some RF getting into the electronics inside the case of the unit - I had CD, cassette, AM/FM whatever else there was at the time so I had a pretty complex system.

I suppose you could try noise suppression on the power side of things - but if that's happening, I wonder how clean the power out of the alternator is, what sort of ripple there is.

This whine picks up in pitch the higher the RPMs. What can I do to clean the power up out of the alternator?

 

[j.o.y.ride]

This whine picks up in pitch the higher the RPMs. What can I do to clean the power up out of the alternator?

Yes that's basic classic alternator whine. It's not a cleaning issue. I promise. You simply have a cable hooked into something or run in proximity of something (or amp itself in proximity to something) it doesn't like. It's a basic issue.

 

[red/green hawk]

Yes that's basic classing alternator whine. It's not a cleaning issue. I promise. You simply have a cable hooked into something or run in proximity of something (or amp itself in proximity to something) it doesn't like. It's a basic issue.

I might have to move my amp but I'll try grounding it to the battery first.

 

[ShadowsPapa]

This whine picks up in pitch the higher the RPMs. What can I do to clean the power up out of the alternator?

You can try the ground, try moving the amp, and there are filters that you could try on the power input of the amp. I'd try the other things first.
As far as the alternator itself - to know the health of that, you'd need to scope it.
It's what I do when restoring alternators or building them. I put them on a scope and watch the output pattern for excessive ripple. Bad or weak diodes in the old-school alternators caused whine - sometimes you could actually hear it whine just at the alternator.
A lot of weird things can happen with bad or weak windings or diodes.
Modern alternators are a whole lot cleaner output than those of 2 or 3 decades ago - but I have an article showing how one shop fixed fuel injection system problems by fixing the alternator. It was putting ripple into the system that the PCM didn't like.

I find it interesting that several of us have heard a whine in the audio systems of our JTs when in reverse (automatics) - we called it a ghost moaning or whining in the system. These aren't without electrical imperfections.

Alternators are AC generators. They generate alternating current. That output must be rectified, changed to DC. There's a lot of EF around the alternator itself because it's an alternating current, and the output can be unclean in some cases (but so far I don't recall seeing anyone with a modern Jeep having alternator issues)

Below is a pic of a scope I had years ago - checking the output of an alternator to diagnose issues.
Wow, that was old..........

 

[Kevin_D]

As far as the alternator itself - to know the health of that, you'd need to scope it.

A decent modern DVM will be able to read AC ripple in millivolts, too.

Kevin

 

[ShadowsPapa]

A decent modern DVM will be able to read AC ripple in millivolts, too.

Kevin

Yes, but being a visual person - I also like to see the pattern on a scope. It's faster for me to recognize other things going on.
I have an older Fluke and still use my analog meters for some things.

 

[Radio Guy]

Alternator whine is usually caused by one of two things, a bad alternator or ground loop. The way alternator noise propagates in a ground loop situation is the amplifier and another component of the stereo system are at a different ground potential and the RCA or low level audio cable shields between the components are trying to equalize the potential and current is flowing on them, inducing any and all noise in the battery/charging system into the low level audio cables.

The easiest way to fix this is with a capacitor type ground lifter or isolation transformer in the low level audio cables, which breaks the DC current path. Here is a cheap fix, never used this brand but it should work. https://www.amazon.com/InstallGear-Ground-Isolator-Noise-Filter/dp/B077Y5DLBB/ref=sr_1_1_sspa?crid=11ZCLQA0HHSZC&dchild=1&keywords=rca+ground+loop+isolator&qid=1628455091&sprefix=rca+ground+,aps,201&sr=8-1-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEyMVY3QVBPTkVXTkQ2JmVuY3J5cHRlZElkPUEwODkyMDUxMkY1RVA5NkQwT0M2JmVuY3J5cHRlZEFkSWQ9QTAyODkzMzMxUEJONU0xTFYwQzQyJndpZGdldE5hbWU9c3BfYXRmJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==

This one may be better quality and I have not personally tried this brand. https://www.amazon.com/XtremPro-Hi-...a+ground+loop+isolator&qid=1628455437&sr=8-13

 

[ShadowsPapa]

Sounds like why the guys I dealt with when buying equipment always advocating taking components to the same ground point - don't ground one thing at the dash and another under the hood and another in the rear of the vehicle. They said ground to the same point, a common ground. I recall them advising me years ago "avoid ground loops"

"Bad alternator" - typically diode (weak, bad) or stator issues.
All can be fixed.
When an alternator is fully loaded like I do on my test stand you can sometimes hear the problem in an audible whine coming from the alternator itself.
On these you'd probably know if there was an alternator issue - they would likely have trouble keeping up with full loads. Watch for abnormally low voltages.

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