Chassis Ground for Amp Hookup?

[mellowtoad]

Hi folk,

I'm installing a 300 watt amp to power my Alpine Type-S 6.5 inch speakers. I've mounted the amp under the passenger side dash with my power hooked up to the battery and the ground hooked up to a screw/bolt combo to the left and above the battery.

Even though this appears to be a good ground area, I'm still getting a lot of engine feedback in my speakers. This is also not the first area that I've grounded it too, I've tried all of the different possible screws and nuts around the battery but have had the same issue.

Does anybody know if there is a better ground area to use? Just some other notes, I'm using a 4 gauge power and ground wires and have also tried grounding to the batteries negative, as well as to the wire that the batteries negative connects to.

Thanks in advance, you all are great!

[cubefx]

Main rule is to to to keep the ground wire as short as possible.

Check if your speakers wires anywhere near your power wires. You need to keep them away from any electrical wires. That is might why you getting engine whine.

Also you might consider getting more expensive shielded speaker wires.

[lebikerboy]

You might also want to change your main chassis ground cable as well...
Evilution - Smart Car Encyclopaedia

[mendo]

Always best to connect both the positive and the ground leads from the amp directly to the battery with the same length and gauge wire.
Always put a fuse as close to the Battery as you can on the positive cable.

[cubefx]

Originally Posted by mendo

Always best to connect both the positive and the ground leads from the amp directly to the battery with the same length and gauge wire.

With all due respect I strongly disagree. In the regular car (battery in the engine compartment) only positive wire going thru the firewall. Ground wire always connected somewhere near the amp to the body of the car. Yes, in the Smart he can connect both wires directly to the battery just because of location, but it is not necessary.



Here is quick "How to" on Amp installation.

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STEP 4
Find a metal bolt or screw on the metal of your car near the amp to connect the ground cable to. This should be as close to the amp as possible, never more than 3 feet. Unscrew it and clean the metal surface with sandpaper. Attach the ground to it with the o-ring and screw it back down firmly.

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[mendo]

That is fine for small amps with low current draw.

Remember that all the power going out to the amp through the red wire must get back to the battery. If you use the car, you are sending that current throughout the whole car. if you use a dedicated wire you get it right back to the battery. If you amplifier draws 50 amps of current and you use the body, you run 50 amps of current back to the battery through every piece of metal in the car. Could be a way for noise to get into the system. (it has been for me, and was cured by wiring directly)

Take a look at any of the autos in the large stereo contests and you will see dedicated wiring for both the hot wire and the ground.

[cubefx]

Originally Posted by mendo

That is fine for small amps with low current draw.

Remember that all the power going out to the amp through the red wire must get back to the battery. If you use the car, you are sending that current throughout the whole car. if you use a dedicated wire you get it right back to the battery. If you amplifier draws 50 amps of current and you use the body, you run 50 amps of current back to the battery through every piece of metal in the car. Could be a way for noise to get into the system. (it has been for me, and was cured by wiring directly)

Take a look at any of the autos in the large stereo contests and you will see dedicated wiring for both the hot wire and the ground.

Noise Prevention

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VII. Keep amplifier power ground wires as short as possible. The longer a wire, the more resistance it has. When a current flows through a resistance, a voltage drop is produced. Because of this, the ground reference at the amplifier's circuit board is no longer the same as that at the chassis of the vehicle. This ground potential differential can lead to noise and improper operation of the amp.
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BTW, Mellowtad read the article, it might help you to fix your noise issue.


CUBE

[mellowtoad]

Does this make a difference? My amp is right below the passanger side dash, but is connected via a 'normal' 4 gauge 20 foot long power line, my ground is 12 inches, same gauge. Is that length maybe causing a problem? It's currently bound up in a ball since it's much longer than what I need.

[cubefx]

Originally Posted by mellowtoad

Does this make a difference? My amp is right below the passanger side dash, but is connected via a 'normal' 4 gauge 20 foot long power line, my ground is 12 inches, same gauge. Is that length maybe causing a problem? It's currently bound up in a ball since it's much longer than what I need.

Here is your problem. With 20 feet of wire you can wire 10 smarts.

[mellowtoad]

Just want to verify:

'Hot' = 15 - 20 Feet

'Ground' = 11 inches

So, I should go ahead and cut it? I paid a lot for the cord, haha. I'll give that a try and report back.