Ewww, ground noise finally isolated, now wut!?

**sdashiki** · 03-25-2006, 10:10 PM

Well, I finally got a new head unit to tide me over until the carputer money starts rolling in. My last one was 8yrs and counting, still works...on ebay as we speak...anyway...

I have always had a little bit of static, in the past months, which I narrowed down to the RCA wires that stuck out from the back of the HU itself, jiggle em and static would "jiggle" too. And most recently when I installed new components in the rear, I got engine whine.

So I figured why not just change out the ol girl. And I did.

Engine whine still there.

Disconnected RCAs from amp (5 channel amp running all interior speakers) and still engine whine. So that narrows it down to the amp alone.

Its a Rockford Fosgate 600.5, sweet amp. The +/- are 4G wire, and the ground is connected with a gold plated square donut end thru a bolt that goes to the chassis holding the back seat bench down. It was a ***** to ratchet on and off.

So since its narrowed down to the amp, is it most positively a grounding problem?

Is it that what I thought would suffice (the bolt itself, because i did NOT scrape any paint, but the car is silver so I might have thought it was bare, i mean its under the seat, but a coating is a coating) is not good enough and I should unbolt it, scrape the paint and try again?

I have had this setup (sans the new HU and rear components) for 4 yrs now. And I think maybe I have had this all along, but didnt notice. The rear speakers were powered by the HU, and the fronts (components) were off the amp. Now with rear components, the front and back are run by the amp, and nothing by the HU. So with my whole sound field with the ground noise problem, I notice it now...or its a possibility.

I just dont want to have to ratchet that ***** again, ill have photos to show you how and why.

**sdashiki** · 03-26-2006, 09:23 AM

Well here you can see where the ground is attached. To the bolt holding the back seat down.
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I thought the bolt, going thru a hole in the chassis, would carry the ground signal thru the chassis, to the bolt to my gold connection. And it DOES, because the amp is on, and works fine. Its the ground niose/engine whine thats the problem.
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Does this connection look bad/good to anyone?
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The amps wires might look "ugly" but they are a solid connection, usually that crap is hidden under the amps wings.

**TheLandYacht** · 03-26-2006, 01:20 PM

Ok...here's my take.

That close-up pic of the bolt and metal around it where you are grounded looks nice and pretty and BLACK.

Black isn't the color of bare metal. Bare metal is ESSENTIAL to good ground. Get a grinder or sandpaper or something and grind it down til there ain't a speck of paint within an inch of the bolt and THEN torque that sucker down nice and tight.

Yes you have "a ground". If you have paint in the way, however, your ground isn't good enough. You could read the result with a multimeter if you have one. Set it to resistance (ohms), put one lead on that gold terminal, and the other on a bare piece of the chassis somewhere else (or the black terminal on the battery if you can reach that far). Any reading above 1 ohm is classified as a "not good thing". Resistance means a voltage drop across the chassis, and will almost always result in noise of some sort.

**tj!2k4** · 03-26-2006, 01:28 PM

**sdashiki** · 03-26-2006, 01:58 PM

yeah i figgered as much, just been 4 years, and didnt notice the noise. but its cuz the front components were the only thing running from the amp. I had the rears by the HU.

Now with components all around, nothing but the amp is used.

So i just didnt notice it, and now its obvious. So only now do I see that the ground is crap.

Ill take a whack at it with a multimeter while I grind away the paint on a different bolt, that one is too hard to sand (gotta wedge the hand inbetween the seats as they fold down)

**furball69** · 03-26-2006, 04:44 PM

Have a look at this post and see if it is able to help, if fixing your amp ground doesn't solve the problem.

Alternator Whine Only With Carputer

**TheLlama** · 03-26-2006, 06:19 PM

Your amp comes on because you do, infact, have a ground. Most likely through the RCA cables though. Hence, your ground-loop.

**sdashiki** · 03-26-2006, 06:25 PM

the reason I know it IS the amp is that disconnecting the rcas (all 3 pairs)....

leaves the amp by itself. sending "silence" to the speakers

the amp is hooked up to all 10 speakers (thru crossovers) and the noise remains without any connection to the HU or RCAs.

its the amp.

from wut I hear, its the quality of my ground

**RedGTiVR6** · 03-27-2006, 09:07 AM

ok - the thought process above regarding the grounding point, is somewhat correct

however...

it's not a good grounding point

you have carpet below that. Sure, there's contact from the bolt to the rest of the body, but it's not good enough IMO.

You need to connect to something that's metal on metal, ALL THE WAY THROUGH.

Find a new grounding point.

And, please, do something with that duct tape!

That alone leads me to believe that your install is faulty all around and just needs to be pulled out and done right.

**sdashiki** · 03-27-2006, 01:46 PM

LOL, no my install is perfectly fine and installed well, its the 3rd car ive owned and done myself. And the orignal ground point was the ground connector threaded on a bolt that was directly on the chassis holding the rear seat down. I just never sanded or anything.

The electrical tape (not duct) was to denote the ground vs the power since they are both red.

Ok, so new chapter in the story as follows:

moved the ground point:
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as you can see its metal on metal, I didnt undo the bolt (no ratchet at time of photo) but its bare metal, sanded with paper and scraped with a pointy metal spike to gleaming chassis. so this connection is 100% "cleaner" than the last ground I had.

so you would think it would solve the problem.

it didnt.

didnt even get slightly get better or worse, its the same.

so I figured, ok Ill clean the ground cable AT the amp.

So i recut the ground 4G wire to nice clean copper and plugged it back in.
And I did the same to the positive wire too.

Still the problem is the exact same.

I have yet to touch it with a multimeter (frend outta town), but I am starting to think the amp is buggered or something itself?