Alternator Whine Options

[GTS13]

Hey guys,
I just finished installing my new 6 channel amp but now have alternator noise. I've already redone my ground on the amp moving it to a different location even and that didn't fix it. I also bought a couple Ground Loop Isolators and those didn't fix it either so I returned them. Any other ideas on what to do? Only other thing I can think of would be to replace my alt with a bigger one?

The amp is a JBL GTO 755.6 II.

Thanks!

[BloodyStupidDave...]

Hey guys,
I just finished installing my new 6 channel amp but now have alternator noise. I've already redone my ground on the amp moving it to a different location even and that didn't fix it. I also bought a couple Ground Loop Isolators and those didn't fix it either so I returned them. Any other ideas on what to do? Only other thing I can think of would be to replace my alt with a bigger one?

Replacing the alternator is unlikely to help. It could be a alternator going home but short of replacing it, it will be hard to prove that is the cause.

You are much more likely to be on the right track looking at the ground loop. A quick and dirty way to fix this that often works is to disconnect the ground wire of the phono between the amp and the head unit on one end (it doesn't matter which end as long as you choose the same end for all the phonos running between amp and headunit).

If you are using home audio style figure-of-8 audio wire between your amp and you head unit, consider replacing this with high quality car audio coax cable. Coax cable has a central core for the signal and is surrounded with a ground screen.



The above picture shows a solid inner core and a steel and aluminium screen but the one you want has multi-strand inner core and copper screen. Make sure to get coax designated for high quality audio applications and make sure it has the foil screen as well as the braid (copper foil is okay).

Try running a dedicated negative (ground) wire directly between the amp and the head unit. Use the same type of wire as the negative wire feeding the amp. If the whine is still there, keeping the dedicated ground wire in place between amp and headunit, try disconnecting the negative wire between battery and amp (so that the return path for the amp is via the headunit). If the negative wire from the battery to the head unit isn't up to the job of taking the load for both devices then do the following instead:

Keeping the dedicated ground wire in place between amp and headunit, try disconnecting the negative wire between the battery and headunit (so that the return path for the headunit is via the amp). Don't do this if the negative wire from the battery to the amp isn't up to the job of taking the load for both devices.

Try providing a dedicated ground wire from the cage the head unit fits into, to either the grounding point for the amp, the grounding point for the head unit or back to the battery.

Try rerouting the phono wires between the amp and the headunit away from all other wires especially power wires.

Try buying some copper or steel overbraid and feeding the wires between amp and headunit inside the braid, then connect the braid to either the grounding point on the headunit or on the amp. Alternatively, you could wrap the wires in copper or aluminium foil and similarly connect the screen to one of the grounding points.



It really comes down to trial and improvement.

Further reading:
http://www.caraudiohelp.com/newsletter/alternator_whine.htm
http://www.termpro.com/articles/noise.html
http://www.crutchfield.com/S-NXNKOqJ7sih/tech/kb348.html
http://www.eham.net/articles/15113
http://www.talkaudio.co.uk/vbb/showthread.php?p=1949352

This post has been edited by BloodyStupidDavey: Aug 5, 2007 - 3:22 PM

[soven]

Do you have a pioneer headunit?

[GTS13]

Do you have a pioneer headunit?

No I have a Kenwood EZ500. It's all on my profile.

[GTS13]

Ok, that's a lot of stuff Davey. I have my head unit hooked up that I did about a year ago and it has the ground that connects to the stereo's wiring harness. And then I just ran the RCA cables from my head unit to my amp along with the signal wire. Then there's a ground coming out of the amp and grounding to another part of the car.
So you're saying the ground for my head unit and amp should be connected?

[jesterwr217]

Ok, that's a lot of stuff Davey. I have my head unit hooked up that I did about a year ago and it has the ground that connects to the stereo's wiring harness. And then I just ran the RCA cables from my head unit to my amp along with the signal wire. Then there's a ground coming out of the amp and grounding to another part of the car.
So you're saying the ground for my head unit and amp should be connected?

no they have separate grounds move your power wire for your amp

[pittfirefighter]

jester is on the right track for one possible cause... the power wire and RCA wire for the amp cannot be put next to each other you'll get magnetic alternator whine from that... the shielding that Davey talked about will protect from the magnetism fields... or just move the power wire to fix that... if ground loop did not fix it then changing the ground point does not matter... the two spots are of equal potential... so check power wire

[BloodyStupidDave...]

So you're saying the ground for my head unit and amp should be connected?

That is a thing to try, yes. As pittfirefighter said, a common cause of alternator whine is a difference in potential between the ground at the amp and the ground at the headunit. Because bodywork and wires have an electrical resistance, when things are connected to different ground points, there is a possibility of there being a small voltage difference between the different ground points. My reply above gives a number of different strategies to check that all the metalwork and the ground points on different bits of your audio setup are all at the same voltage.

But the point that jester (and the other point that pittfirefighter) makes is equally valid: alternator whine can be induced in the RCA cables if any power wires run close to the RCA wires. This is where the various shielding strategies I outlined come into play: rerouting the RCA cables away from any power or any other signal wires is important. Alternatively (or additionally), replace your RCA cables with ones offering better shielding characteristics or supplement the shielding on your existing cables.

This post has been edited by BloodyStupidDavey: Aug 5, 2007 - 4:46 AM

[GTS13]

Ok well I didn't just use any old ordinary RCA cables. I paid decent money for some Streetwires that are shielded rather well. The power runs on the driver's side of the car and the RCA cables run down the middle of the car through the center console and the only point that they cross paths is to enter the amp.

Here's a link to the RCA cable that I'm using. http://www.crutchfield.com/S-SzBUbULqCqF/c...amp;I=211ZN7435

This post has been edited by GTS13: Aug 5, 2007 - 3:23 PM

[BloodyStupidDave...]

Ok well I didn't just use any old ordinary RCA cables. I paid decent money for some Streetwires that are shielded rather well. The power runs on the driver's side of the car and the RCA cables run down the middle of the car through the center console and the only point that they cross paths is to enter the amp.

Okay. Any you say that the ground loop eliminator didn't work for you either, so breaking the RCA earth connection on one end (which is effectively what the ground loop eliminator does, but with clever electronics) isn't likely to help. At this point, your best bet would seem to be to use some heavy gauge wire and try grounding things together in a trial-and-improvement way. Basically paragraphs 5, 6 and 7 from my first post.

[jesterwr217]

run the rcas down the passenger side

[BloodyStupidDave...]

run the rcas down the passenger side

Hmm. What runs down the center console? Handbrake sensor, ashtray light, aerial coax, possibly security system. Should be okay. Where does the power antenna wire run? I assume drivers side.

[AudioFreak]

One thing I've always used to find the source of a ground loop is to use shorting plugs.

This is what you need to make. You can make these without the resistor and just use a loop of speaker wire.



Start at the amp. Unplug your cables and plug in the shorting plugs. Start the car. If you have noise it's coming from the amp or it's wiring. If not move on to the cables themselves.

Plug the cables back into the amp and unplug them from the headunit. Using some female to female rca adapters connect to the cables and start the car. If you have noise try moving the cables. Or better yet just try another set of RCA's and see if fixes it. I've seen bad cables out of the box even expensive ones.

No noise... it's coming from the headunit. Try grounding the headunit somewhere else.

DO NOT PLUG THE SHORTING PLUGS INTO THE OUTPUTS FROM THE HEADUNIT!!! IT WILL BE BAD, VERY VERY BAD

One other thing to check is the condition of the grounds under the hood. I think there are 3 total. 2 off the battery and one off the engine. Pull them off one at a time clean the surface and ring and reconnect. It doesn't hurt to clean these every so often. When I bought my celi the lights would dim every time I hit the brakes until I cleaned the grounds in the engine bay. There was also a little bit of alt. whine until I did this.