mofologic

I asked this in the audio forum and didn't get a definitive answer, so I have come back to the forum I know to ask. I am installing a power amplifier in the trunk and am curious if i could use the battery for ground or would I be better off using a chassis ground? I realize that the chassis ground would be shorter, but it is not that much further to the battery as the amp is going to be mounted on the ski sack cover. Thanks in advance....

a-talk

When I did my stereo install on my old '87 Avant, I went straight to the battery. I figure any chassis ground is linking back to the battery anyway. Audi makes it pretty easy to install stereo equipment in their "mid-battery" cars .

<img src="http://pictureposter.audiworld.com/76987/amp1.jpg">

<img src="http://pictureposter.audiworld.com/76987/subfloor.jpg">

mofologic

thanks for the pic and suggestion - i wasn't sure if the amp would fit under the rear seat, but after seeing your setup, i tried and sure enough it did! short of the sub enclosure in the far front of the trunk, it is an invisible install!

a-talk

Make sure to put something between the amp and the body metal - I used some thin black foam I found at the local craft store. Good luck - stealth installs are the best!

AK_92_V8

and hooked it up to the ground wire that was already there and put it back together it has a whistle to it when i drove around. Haven't got around to fixing it but if you run a new ground wire it fixxes that problem. Just a heads up

a-talk

Had this problem too - ground that head unit straight to the metal!

AK_92_V8

only i lost the pins to remove the head unit so its stuck in pland and im SOL

a-talk

I made some pins out of nails with my grinder and some locking pliers once when I lost the removal tool. Not graceful , but it worked fine.

cuatrokoop

Ground and battery negative are not the same. Circuits with IC's and other such devices can be sensitive to ground vs negative. Not everything can use a negative pole as a ground.

ColoQuattro

So you don't get a a stray ground signal from the body of the amp connected directly to the chassis of the car. Screw the wood seperatedly to the chassis and the amp seperately to the wood. After that, grounding to the caassis with a heavy gauge wire or grounding to the battery is not a big deal. You want to have a larger gauge ground wire that power wire. The head unit ground from the factory is fine as the amps are isolated from the head unit. If you ground to the chassis make sure that you grind the paint off where you choose to ground.
Most ground to the chassis because grounding to a battery at the front of the car is expensive due to the cost of wire. In our case going straight to the battery is easy and eliminates chances of stray "noise sources" and gives you a cleaner connection and isolation, somewhat like having a UPS/surge protector or an inverter on your computer. No power spikes, ignition whine, power drops, etc. With a UPS Your computer gets its power from the battery which is constantly charged from the 120 VAC. That's also why you always hook your positive AMP leads to the battery and have a "remote on" relay to power the amps.
All said if you can go to the battery for your + and - all the better. Just make sure that you are fused on the + side about 16" from the battery.
Hope that htis helps :+)