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Does this guy know what he is talkin about?

Old 03-01-2007, 08:57 AM
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Arrow Does this guy know what he is talkin about?

Ok, so I was on another forum asking questions about my engine whine and like 11 out of 12 of the reply's told me that my ground wire was way to long (since it is grounded to the battery) and that I should shorten it up and ground it to the body next to the amp. But I am kindof skeptical considering a member on this forum (I think it is Prolifik?) has like 8 runs of wire to his battery for a ground and doesn't have any problems.

So I asked for an explanation and some dude said this:

Originally Posted by CarAudioForums
Copper wire has some inherent resistance. This resistance is based upon (among other factors) the wire's length. So, when you run a super long ground cable you have a voltage drop across your ground wire. This means your amplifier/components don't actually set at zero volts. So, if you run a short ground wire for your H/U and a long wire for your amps there will be a systematic offset induced on your components.

When you have a voltage offset like this, it allows noise to be induced in your system. So, by reducing your ground length you will decrease the possibility of this noise being outputted to your speakers.
Does this make sense? I would have waited for him to reply on the other forum but I need some fast answers because it is a snowday and I plan on finishing my system today. So any help would be appreciated, thanx guys.
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Old 03-01-2007, 09:46 AM
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That is true.
The body and frame of a car provide a very large ground path compared to a single run of 4 guage wire.

Adding a copper ground to your ground points can't hurt, but DO ground all your components to the body as close as possible to each piece.

Do not use any metal dash/steering wheel brackets as a ground....stick to painted body panels, preferably thicker or double layered metal (of course clean off all the paint first.

What vehicle do you have?

Never mind...read your sig.

Alt whine usually enters the system at the head unit so I'd start there. The new Chevs have very skimpy wires for the constant lead....run a 10 guage wire to the battery or your 0 gauge wire (fused of course)

Last edited by Starterwiz; 03-01-2007 at 09:51 AM.
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Old 03-01-2007, 10:58 AM
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Ok, after spending like 15minutes trying to retrieve a screw that I dropped down behind the HU I was able to run two 16 gauge wires (thats all I had at hand, lol) from the negative on the battery around the outside of the vehicle and in the window to the negative wire on the ground. That pretty much solved my problem. There is still a hint of whine but I can't hear it unless the doors are closed and it is totally silent inside with my ear right next to the speaker. Do you think if I ran a positive wire from the battery to the hu if it would improve even more?
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Old 03-01-2007, 12:00 PM
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You don't have that much power, and you do have 1/0 both ways... have you upgraded your battery ground too?

I have a feeling that it's the headunit that is inducing noise too... but you could also ground the 1/0 to the unibody near the amps, and then also run your 1/0 ground to the battery. That way the 1/0 to battery would enhance your chassis ground.
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Old 03-01-2007, 12:18 PM
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if this doesnt work let me know

copper conducts better than steel. maybe these guys drive a unibody

l only ground a capacitor to the body. ground to the battery is the way to go.

l had a similar issue, so i grounded everything to a single distribution block, then back to the battery and made sure no signal wires were near power.

guess what. no noise. l competed last summer so this was a big issue that was solved. l had 3 amps ,2 acc, radio and cap.

good luck
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Old 03-01-2007, 12:39 PM
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Use a bit larger wire than 16 ga....10 ga is about right for a head unit....don't forget the fuse!!!

Unless the amp's chassis are isolated from the body, then it's a good idea to ground to the body as well as the copper battery run.

Also the head unit grounds via the antenna, so it's important to have the "same" ground at all the points in the system.

The battery negative post is NEVER the same as the body, once there's some current flowing.
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Old 03-01-2007, 01:00 PM
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Think about what lay in the path of a ground return through a vehicle. Crappy welds, small ground wires, glued together unibody panels. These all contribute to a higher than average ground resistance. It is not about the amount nor size of the metal in the return, it is about the resistance through it. The PROPER thing for a installer to do is measure the return resistance. If the reading is over 1/2 ohm, you have a bad ground and you need to find a different grounding spot. If it cannot be found, then off to the battery you go.
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Old 03-01-2007, 01:24 PM
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Originally Posted by MR2NR
Think about what lay in the path of a ground return through a vehicle. Crappy welds, small ground wires, glued together unibody panels. These all contribute to a higher than average ground resistance. It is not about the amount nor size of the metal in the return, it is about the resistance through it. The PROPER thing for a installer to do is measure the return resistance. If the reading is over 1/2 ohm, you have a bad ground and you need to find a different grounding spot. If it cannot be found, then off to the battery you go.
Good advice.

You can take this theory one step further though. When you measure the return resistance from amp to battery and get a good reading of lets say 1/2 of ohm for example, all this is telling you is that there is 1/2 an ohm of resistance between the two points at almost no current draw. It is when this return path is trying to pass large amperage (when amp is in use) that we need to be concerned about.

When using the cars body as your return path, the current will always find its way back to/from the battery through the lowest resistance path. This path can change at different current demands. I like the predictability of running a same guage ground (as your V+) directly back to the battery in any size system. You then at least know what you are dealing with.
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Old 03-01-2007, 02:05 PM
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It never hurts to improve the ground, but it's still important that all the grounds are the same.

Rather than measuring resistance, try measuring the voltage between various points while drawing some current.
The ideal would be to see NO voltage between any of the grounds.
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Old 03-01-2007, 03:05 PM
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Even though.. it was not recommended by RC & DN (noise video) but it was mainly to avoid picking up alternator noise...... and not about the performance and consistancy.

i have done many Corvettes in the old day, when you have to ground the stereo right at the battery, because the body was fiberglass. and i had no big issue with noise that can not be cure.

Last edited by SweetnLow91SC; 03-01-2007 at 03:13 PM.
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