# Grounding amp at the battery - ok?



## Mless5

Building a small set up for my brother's bmw which has battery on the trunk. Anything wrong with having slightly longer ground cable, but grounding at the battery?

Thanks.


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## robbyho

Mless5 said:


> Building a small set up for my brother's bmw which has battery on the trunk. Anything wrong with having slightly longer ground cable, but grounding at the battery?
> 
> Thanks.


So long as the connection is solid and you don't interfere with the stock connection, then it is no problem. That's how all us with magnums, chargers and 300's do it.

Robby


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## Smiling Bob

How about this: I ran a #10 wire from my batt - to the body at the batt ground, to the HU ground and on to the amps ground where it ties into the #4 amp ground. Is there any reason not to do this? System is almost completely free of any noise, except when my wife picks the music...


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## GlasSman

Smiling Bob said:


> How about this: I ran a #10 wire from my batt - to the body at the batt ground, to the HU ground and on to the amps ground where it ties into the #4 amp ground. Is there any reason not to do this? System is almost completely free of any noise, except when my wife picks the music...


Why would you want to make a *WORLD TOUR* like that tying the HU and AMP ground?

THats a ground loop and inducted noise *WAITING* to happen.

If you need to ground the HU theres always a section of metal behind the dash with an existing star washer and nut/bolt near the HU.

If there isn't one drill it yourself.


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## robbyho

GlasSman said:


> Why would you want to make a world tour like that tying the HU and AMP ground?
> 
> THats a ground loop and inducted noise *WAITING* to happen.
> 
> If you need to ground the HU theres always a section of metal behind the dash with an existing star washer and nut/bolt near the HU.
> 
> If there isn't one drill it yourself.


x2

robby


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## chad

GlasSman said:


> Why would you want to make a world tour like that tying the HU and AMP ground?


LOL'd


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## sqshoestring

I like to ground amps in 3' or less, but if there is a battery slightly further away I'd use it. Any battery should be grounded to body IMO. Yes for noise first thing I do is add ground to HU case, after checking all other grounds.


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## 89grand

Having a battery in the back rules. My amps will be about 1 foot from my battery and grounded there.

w00t!


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## 328iBMW

I had alternator whine when I grounded my amp to my battery in my trunk. I think that it was because the head unit was grouded up front thus creating a potential (ground loop) between the head unit and the amp. :dunno:

My amp is now grounded to the body and the whine is gone.


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## PSYKO_Inc

If you do ground directly to the battery, I'd recommend fusing your ground wire. The reason for this is that if the stock ground strap from the battery to the body were to come disconnected or get pinched/cut somehow, the amp chassis and ground wire become the new ground path back to the battery. First time you try to start the car the amp goes up in smoke, and possibly the wiring as well. The fuse might not save your amp, but it would prevent the wiring from becoming overloaded and starting a fire.


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## chad

PSYKO_Inc said:


> If you do ground directly to the battery, I'd recommend fusing your ground wire. The reason for this is that if the stock ground strap from the battery to the body were to come disconnected or get pinched/cut somehow, the amp chassis and ground wire become the new ground path back to the battery. First time you try to start the car the amp goes up in smoke, and possibly the wiring as well. The fuse might not save your amp, but it would prevent the wiring from becoming overloaded and starting a fire.


Oh ****!!!!!!! [puts on the kevlar jacket due to expierience]


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## Smiling Bob

GlasSman said:


> Why would you want to make a world tour like that tying the HU and AMP ground?
> 
> THats a ground loop and inducted noise *WAITING* to happen.
> 
> If you need to ground the HU theres always a section of metal behind the dash with an existing star washer and nut/bolt near the HU.
> 
> If there isn't one drill it yourself.


Why? I'm a novice at this and it made sense to me. I figured that the current needs a path to ground and that grounding to the body is the same as grounding to the batt, it just uses the body as a grounding conductor. But if there is a rubber mount, a caulked seam, etc in the path to ground then resistance to ground would be higher than it needs to be. 

Wouldn't grounding eliminate stray (inducted) currents (noise)?

If I'm wrong, no problem. I'm here to learn, and mistakes are a lesson..

Great site, BTW. Really cool how different ideas can be discussed in a civil manner, as opposed to the ca.com jailhouse mentality..


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## Hillbilly SQ

my philosophy is to ground the most simple way possible. if you're lucky enough that it's the battery you're golden. otherwise just make sure you're near an area where the floor meets the frame for maximum current flow.


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## PSYKO_Inc

chad said:


> Oh ****!!!!!!! [puts on the kevlar jacket due to expierience]


Uh oh, did I step in something just then?


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## chad

PSYKO_Inc said:


> Uh oh, did I step in something just then?


Nope I went thru that once here and explaining that was like nailing jello to a tree.....


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## tophatjimmy

^ Had to fix this exact thing this week in a guys boat. For whatever reason, the main ground wasn't connected. he tried to start the boat and it pulled ground through his radio. FRIED the radio and incinerated the radio ground wire.


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## chad

tophatjimmy said:


> ^ Had to fix this exact thing this week in a guys boat. For whatever reason, the main ground wasn't connected. he tried to start the boat and it pulled ground through his radio. FRIED the radio and incinerated the radio ground wire.


I see the fekin light! I swear to god when I suggested this once as a safey related item I was hung by my earlobes and hot pickle juice was poured over my nips!

You see folks, The negative battery terminal IS NOT GROUND, the car's body/frame/etc is GROUND, the negative of the battery just hooks up to it


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## dogstar

chad said:


> I see the fekin light! I swear to god when I suggested this once as a safey related item I was hung by my earlobes and hot pickle juice was poured over my nips!
> 
> You see folks, The negative battery terminal IS NOT GROUND, the car's body/frame/etc is GROUND, the negative of the battery just hooks up to it


That being said, how about connecting the amp ground to the body bolt that the battery negative connects to?
Same difference or safe and sound?

I'll admit to sometimes being an electrical idiot, but I don't mind asking questions.


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## pikers

robbyho said:


> That's how all us with magnums, chargers and 300's do it.


Other things others don't need to do that you guys do:

1. Put 22s on
2. Sit sideways
3. Pretend it's just "an American Benz"

j/k


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## chad

dogstar said:


> That being said, how about connecting the amp ground to the body bolt that the battery negative connects to?
> Same difference or safe and sound?
> 
> I'll admit to sometimes being an electrical idiot, but I don't mind asking questions.


I find it easier to find a good ground close to the amp  But in the rear battery deal, hell yeas, right where it bolts to the body



pikers said:


> Other things others don't need to do that you guys do:
> 
> 1. Put 22s on
> 2. Sit sideways
> 3. Pretend it's just "an American Benz"
> 
> j/k


I found that funny.


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## beerdrnkr

chad said:


> I see the fekin light! I swear to god when I suggested this once as a safey related item I was hung by my earlobes and hot pickle juice was poured over my nips!
> 
> You see folks, The negative battery terminal IS NOT GROUND, the car's body/frame/etc is GROUND, the negative of the battery just hooks up to it


I have a rear battery as well as one under the hood. The rear bat has 1/0 gauge wire ground from the frame to the bat negative and I'm running 3 amps from that battery negative as a ground. In my case is it working like a distro? Is this ok? Thanks, kinda related so I thought i'd ask.


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## chad

beerdrnkr said:


> I have a rear battery as well as one under the hood. The rear bat has 1/0 gauge wire ground from the frame to the bat negative and I'm running 3 amps from that battery negative as a ground. In my case is it working like a distro? Is this ok? Thanks, kinda related so I thought i'd ask.


Yes, the issue is with one battery, if you have the amps "grounded" to the battery and isolated from the body like you are suposed to, and the body/engine ground were to fail your "New" ground is your amp line, via the RCA's VIA the headunit which in turn is most certainly grounded to the chassis, Darwinism ensues when you go to start the car.


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## GlasSman

chad said:


> I see the fekin light! I swear to god when I suggested this once as a safey related item I was hung by my earlobes and hot pickle juice was poured over my nips!
> 
> You see folks, The negative battery terminal IS NOT GROUND, the car's body/frame/etc is GROUND, the negative of the battery just hooks up to it


Thats some funny **** dude.

If people viewed the battery as just another accessory and a *LOAD* for the alt they would realize it needs to ground somewhere...and the car body is that place....as it is for your amps and HU.


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## chad

GlasSman said:


> Thats some funny **** dude.
> 
> If people viewed the battery as just another accessory and a *LOAD* for the alt they would realize it needs to ground somewhere...and the car body is that place....as it is for your amps and HU.


It's only a LOAD when the charging system voltage exceeds it's float voltage at it's state of discharge  Until then it's a supplier or source.


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## bobditts

robbyho said:


> So long as the connection is solid and you don't interfere with the stock connection, then it is no problem. That's how all us with magnums, chargers and 300's do it.
> 
> Robby


 
and the new dodge challenger


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## chad

chad said:


> It's only a LOAD when the charging system voltage exceeds it's float voltage at it's state of discharge  Until then it's a supplier or source.


In this scenario (open chassis ground) it's an issue when it becomes a high current source and it's looking for the path of least resistance


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## GlasSman

chad said:


> Yes, the issue is with one battery, if you have the amps "grounded" to the battery and isolated from the body like you are suposed to, and the body/engine ground were to fail your "New" ground is your amp line, via the RCA's VIA the headunit which in turn is most certainly grounded to the chassis, Darwinism ensues when you go to start the car.


UH...I cringe at the animation running through my head of that scenario.

And this is what CSI: Miami would find at the end of the episode aptly titled..."Can you fix this"


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## dogstar

chad said:


> I find it easier to find a good ground close to the amp  But in the rear battery deal, hell yeas, right where it bolts to the body


Normally so do I, but for some reason this car was a real ***** to find a ground on. Even the bumper bolts (ground the area down) were ****ty grounds.


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## sqshoestring

An amp would have to fail to ground through the RCA, they are not direct ground or it would make a ground loop and lots of noise. Only the HU is to ground an RCA. Maybe that is another reason why I never ground an amp's case though....was taught that long ago.


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## chad

sqshoestring said:


> An amp would have to fail to ground through the RCA, they are not direct ground or it would make a ground loop and lots of noise. Only the HU is to ground an RCA. Maybe that is another reason why I never ground an amp's case though....was taught that long ago.


We aren't talking about operation, we are talking about what would happen when you release full CCA on that cold morning thru it  PRIOR to operation. Yes, many shields are buffered, dare I say Pico Fuse?  But it still can leave a heap of a mess.


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## sqshoestring

A battery can make a mess, I don't doubt that. But you should have big cables bolted to the car if you have another battery...should be hard to have a failure in ground there but yes it can happen.


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## 12v Electronics

chad said:


> You see folks, The negative battery terminal IS NOT GROUND, the car's body/frame/etc is GROUND, the negative of the battery just hooks up to it


I have to disagree with this. Last time I checked the chassis was just a piece of metal. The ground is "produced" by the power supply (Either the battery or charging system). The chassis is simply a pathway for which these electrons travel.


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## chad

12v Electronics said:


> I have to disagree with this. Last time I checked the chassis was just a piece of metal. The ground is "produced" by the power supply (Either the battery or charging system). The chassis is simply a pathway for which these electrons travel.


The last time I checked the earth was a piece of dirt  That does not make the power grid, or any part of it ground. So on a positive "ground" what's ground? If the stereo were the only thing attached to the battery, sitting in the driveway, then yes the neg is ground.....


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## 12v Electronics

chad said:


> The last time I checked the earth was a piece of dirt  That does not make the power grid, or any part of it ground. So on a positive "ground" what's ground? If the stereo were the only thing attached to the battery, sitting in the driveway, then yes the neg is ground.....


Maybe out car's chassis should be made out of dirt. 

The only electricity the chassis can make is static electricity. It is not earth. A positive ground vehicle is a good analogy. If the chassis produced the ground there would be a big problem.


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## chad

12v Electronics said:


> Maybe out car's chassis should be made out of dirt.
> 
> The only electricity the chassis can make is static electricity. It is not earth. A positive ground vehicle is a good analogy. If the chassis produced the ground there would be a big problem.


I'm certain there are several different views of this, and many can and will argue till they are blue in the face  BTW my truck's chassis IS made of dirt... I swear :blush:

I (and others) look at the "ground" as a point of 0V reference where as you (and others) look at the chassis as a conductor, which IS a conductor as is any ground SYSTEM. The _system_ is what gets people, yes the neg battery terminal in our case is part of the SYSTEM, just like the earth is part of a functional ground system for discharge. Calling the neg battery terminal ground (or positive) only names part of the big picture whereas when you look at the chassis and anything attached to it as the ground encompasses the whole thing.

I see the ground as the chassis, the point at which all grounds or parts of the ground system attach, just as in discharge and PD potential grounding where the earth is the ground.


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## 12v Electronics

chad said:


> I'm certain there are several different views of this, and many can and will argue till they are blue in the face  BTW my truck's chassis IS made of dirt... I swear :blush:
> 
> I (and others) look at the "ground" as a point of 0V reference where as you (and others) look at the chassis as a conductor, which IS a conductor as is any ground SYSTEM. The _system_ is what gets people, yes the neg battery terminal in our case is part of the SYSTEM, just like the earth is part of a functional ground system for discharge. Calling the neg battery terminal ground (or positive) only names part of the big picture whereas when you look at the chassis and anything attached to it as the ground encompasses the whole thing.
> 
> I see the ground as the chassis, the point at which all grounds or parts of the ground system attach, just as in discharge and PD potential grounding where the earth is the ground.


I see where you are coming from. I guess the word "ground" is not the best word to use. I am looking at the battery (or alternator) as the power supply where the positive needs to flow to the negative to have a complete circuit. I work on a bunch of boats where the chassis ground is not present. (I wish it was because it would make my life alot easier)


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## chad

12v Electronics said:


> I work on a bunch of boats where the chassis ground is not present. (I wish it was because it would make my life alot easier)


I lost a little sanity just reading that  That's rough!


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## matt62485

eh good lord if they "grounded" everything in the car to the negative terminal on the battery thatd be one hell of a flustercuck....


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## JoelM

matt62485 said:


> eh good lord if they "grounded" everything in the car to the negative terminal on the battery thatd be one hell of a flustercuck....


Bingo! What if you grounded everything to the neg temminal of the battery? Think about it... The chassis is the least point of resistance. Just go from there. How much metal is in the chassis as opposed to running a wire to the battery?


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## chad

JoelM said:


> Bingo! What if you grounded everything to the neg temminal of the battery? Think about it... The chassis is the least point of resistance. Just go from there. How much metal is in the chassis as opposed to running a wire to the battery?


Well... They do it on "the other side" of the battery


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## psychotic

I swear I thought I was following this until:

"I (and others) look at the "ground" as a point of 0V reference where as you (and others) look at the chassis as a conductor, which IS a conductor as is any ground SYSTEM. The system is what gets people, yes the neg battery terminal in our case is part of the SYSTEM, just like the earth is part of a functional ground system for discharge. Calling the neg battery terminal ground (or positive) only names part of the big picture whereas when you look at the chassis and anything attached to it as the ground encompasses the whole thing.

I see the ground as the chassis, the point at which all grounds or parts of the ground system attach, just as in discharge and PD potential grounding where the earth is the ground."


Anyways, it is obvious to me you will have people disagree and argue in circles about this because we are leaving out symantics... our idiodic nature of using the same terms to describe something completely different.

I too would associate chassis with 'ground', but I would also associate chassis with 'negative', and the neg. terminal with 'ground', and the neg. terminal with 'negative' 
this can be quite confusing...

Cars used to have the POSITIVE terminal hooked up to the chassis... it was still refered to as the 'ground'... a positive grounding point.... we would be even more confused...

What we all call 'ground' in an automotive electrical system is really a NEGATIVE ground... it has current flowing through it, it completes an electrical circuit.

So refering to the chassis as a grounding point, is not technically correct when refering to electrical engineering.... HOWEVER, it is perfectly correct when refering to automotive engineering... text books, etc will refer to this point as a 'ground' in defiance of the technical definition (ex: same books would call the point a ground even if it was an old car, or mainly a lot of older tractors, which used the positive terminal when grounding).

When you say you look at the ground as a point of 0v reference, and the chassis as a conductor as is any ground system, key word being system, aka part of a circuit.... the 0v reference is known as a "SAFETY GROUND", which would be found in the electrical wiring of a home... 
picture: 
positve slot, negative slot, and below and between the two, a circular "ground"

Now how can this make sense if the Neg. is supposed to be the ground???

Well, to clarify this dicussion I think it would help if we clear up the terms we are talking about...

**NEGATIVE GROUND / CAR GROUND / CHASSIS GROUND: a large conductor connected to the negative of a circuit (ex: car chassis connected to the negative battery terminal)

**SAFETY GROUND / 0V GROUND: a ground that does not conduct any current. It is usually run to the ground (read: earth, dirt, 0volts) (Ex: the 3rd wire on an electrical 'main') This type of ground is a safety percaution to guide high voltage current away from other electrical equipment and people, as well as cause fuses/circuit breakers to stop the current flow. It is also used to protect sensitve currents from interference.

**POSITIVE GROUND: If you are working on an old tractor, or a car that is made prior to the 60s 

I too used to associate ground/negative as interchangable terms with the same meaning... 
BUT
I think using THESE terms for clarification will help everyone...


Taken from CR4 forums:
http://cr4.globalspec.com/thread/22501/Ungrounded-DC-Systems
{{{{
"Most DC circuits are never ever connected to ground, your portable radio, your mobile, any aircraft, your car, your electronic watch etc etc etc, but they still work.

A connection to ground is not a requirement for almost any circuit (let alone DC circuits) to work!!!!

Connecting to ground certain parts is usually needed when high AC volts are used to help protect the user from fault currents.....

Sometimes ground is used to shield sensitive signals from interference from other signals....."

"A true ground is a safety feature and does not have any large current running through it, at best nothing at all! It is only there to protect people (and other equipment, but primarily people) from high voltages and a current on the ground should cause fuses and/or other safety devices to swiftly act and cut off the main power....

A cars chassis has current running through it and is part of the circuit. Therefore it is NOT a safety ground ever. Ground in this case is really just a common name that has got attached to the chassis.....I suppose calling it "negative ground" would be a little better than just calling it ground....."

}}}}





As well, this discussion has got me thinking of another issue that may be causing symptoms of what I believe to be an amp ready to go bad...
previously, The amp would sent straight alternating current to all channels upon turning off my car (yes, like hooking up a batt to the + and - and the speaker pops out, flip it around and the speaker pops inward...). This would occur very fast, approx 8 times in less than a second... ...budadudadudadudadu... 

That scared the crap out of me, and I always thought it was going to kill my speakers.... 

I removed the amp, and was supposed to receive an RMA number, which was most likely lost when I moved... So a few months ago I opened the amp up to check for problems....First thing I realize... the warranty sticker had been cut perfectly with a razor and then overlapped (as if it wasn't noticable), which lead me further into thinking the issue lies with the amp (had i received a ****ty board inside the manufacturer's shell?) 

I noticed nothing wrong with the amp upon visual inspection... other than the ground for RCA connections was simply a single metal to metal (slightly touching). The RCA ground 'connection post' w/ ridges visual: [ ()-)>> ] that secured the circular RCA metal ground ring from the amp inputs... these two 'posts' on each side of the cylinder-shaped metal RCA ground, slide into the plastic RCA structure inside the amp, and held the outer metal ring in place with the triangular ridges along the posts... one of these posts was guided into a triangular slot in the ground bar (inside the amp, which connected to the circuit board), where the ground connection was made by this very slight metal to metal contact between the slotted 'flanges/posts' that hold the rca's metal surround and the V [>] cut in the bar attached to the board.
(are all RCA connections grounded with this method??? it seems very poor)

I was looking at this, beacuse my Monster Cable RCA had the 'slanted' slots for a better grip / neg. ground... and they gripped so well they pulled the metal surround / neg. grounding for the RCA inputs!! 

months had passed with no sound in my car (not bearable), after opening the amp and seeing nothing wrong... and also seeing that there was no possible way to reach the contact point between the cylindar and Circuit board connection for soldering a better contact... I made sure the outter ring was fairly tight, shoved back into the RCA inputs and assured it made contact with the grounding rod inside the amp... then I hooked the amp back up...

the previous symptoms were gone, but it only took a few days for something else to go wrong. One morning I turned on the stereo, and was quickly trying to shield my ears to a deafening screeching sound. turning down the volume was my first instinct, however this did nothing... changing the input did nothing, finally I knew shutting off the radio would kill the amp as well, and the screeching stopped.
Later, with the amp inputs turned all the way down, and the EQ/preamp removed to eliminate it as the source of the problem, I hesitantly turned the radio back on... the sound was clear again, however... as I turned the volume up on the radio or the amp input, it would begin to make random pop and screech noises, slightly above what I would consider a mid volume level (with a max being the max volume WITHOUT distortion)....

The eq/preamp tested to be working just fine with RCA input/outputs on some home speakers that I did not care much about testing on.... The amp, however, responding with odd behavior to increased RCA output... appears to still be the culprit, especially considering the high screeching was when the pre-amp (sending 9-volt RCA pre-outs) was hooked up.

This discussion makes me wonder, could a loose or weak amp neg to chassis ground cause anything like this??? is it related to the RCA ground like I suspect?? And does anyone know if this is signs of an amp simply going to ****??

Thanks!!!

Oh, and sorry for posting this in a different topic... I should probably create my own thread, but the posts made me thing of it. 
I do hope the language clarification helps everyone understand the information in this post better!


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## chad

Everything you just said proves that the chassis is ground, ground "shield" and signal are two different things one should be privy as to how each component is configures and the schemes used in car audio for unbalanced connection, there are little to no standards search "alternator whine," While searching you may note that "moving the ground" sometimes helps with this due to the fact that different potential 0V references can exist, just like in the earth. Pos or neg, it don't make a difference, the ground is simply a reference to 0V, you are looking WAY too far into this, we all know conventional the theoretical current flow. It's a point of reference. For example, my lightning protection, it can get hit with a pos strike or a neg strike (50/50 chance), does that make the GROUND potential pos or neg? It don't make a difference, it's a universal common and it works well, proven by the finger of god himself. You gotta have one reference point, that point is ground.

Chad


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## 12v Electronics

Just to clarify my previous post, I understand that the chassis is used in the car's *system* as a ground, however, it is not necessary. Every electrical item would work perfectly without it. This is my argument with what you said. I am not arguing the benefits of using it as a ground but if we had plastic cars they would work fine too. 

Fortunately the "finger of God" is pretty much under control in a car's electrical system and ligtning stikes to a car are pretty uncommon.


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## chad

12v Electronics said:


> Just to clarify my previous post, I understand that the chassis is used in the car's *system* as a ground, however, it is not necessary. Every electrical item would work perfectly without it. This is my argument with what you said. I am not arguing the benefits of using it as a ground but if we had plastic cars they would work fine too.


Well no, ground loops would be MORE common, think about your boats, what if you took a copper strap and ran it the length, would it have more or less resistance than the chassis of a car? And before you get cocky  it would probably have less  Ideally, if I had the time I'd run a strap from front to back bonded to the chassis at different points. More different gauges of wire even star "grounded to the neg battery terminal WILL constitute as a ground "system" but will suck.

Take the battery out of the scenario...... what's the ground? The battery simply derives at what potential the ground will be as a drain, that's it. Look at a power amp, to the negative rail, what potential is ground?



12v Electronics said:


> Fortunately the "finger of God" is pretty much under control in a car's electrical system and ligtning stikes to a car are pretty uncommon.


I had a Monte Carlo with an after market sunroof that wold disprove that, cars get hit all the time, and a GROUNDED frame to earth via a wet tire shields your ass from it coming thru  Why d you think they tell you NOT to get out of the car in a storm, cars are safe. And you know what? The car's ground will raise UP to or DOWN to the potential of the dispersed strike and nothing should die. do you know why? because it ALL stays at the same potential, the WHOLE thing floats up (or down and back to the battery's rest. A Faraday cage, was the car a neg or positive potential? Depends on the strike polarity  My description as to why a single neg waire should be fused going to the battery describes that to a tee, the car is ground. The battery derives the potential, there's no other reason they would call it a _Positive Ground._


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## Smiling Bob

chad said:


> Ideally, if I had the time I'd run a strap from front to back bonded to the chassis at different points. [/I]



How is that functionally different than when I said:


"How about this: I ran a #10 wire from my batt - to the body at the batt ground, to the HU ground and on to the amps ground where it ties into the #4 amp ground."

The idea I had (and was poked fun at for posting... "world tour..") is the same thing. Just trying to assure that all ground points used had the exact same potential.


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## 12v Electronics

chad said:


> Take the battery out of the scenario...... what's the ground?


There would be none. If the car was running the ground would come from the charging system and be delivered through the chassis in our current system.

I know the car acts as a Faraday cage, but still does not explain how it is necessary in a car's electrical system for a ground.

Am I blue in the face yet?


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## sqshoestring

psychotic said:


> I swear I thought I was following this until:
> 
> "I (and others) look at the "ground" as a point of 0V reference where as you (and others) look at the chassis as a conductor, which IS a conductor as is any ground SYSTEM. The system is what gets people, yes the neg battery terminal in our case is ...............................................................................................................................................


Come on you guys, negative ground. They call it ground because it is common to all like the ground is. You can hook the negative anywhere on the car.

As far as your bad RCAs on your amp, they can screw an amp up something fierce. If you want to see if it works right you need to fix that first, even if you hack an RCA cord and solder it into the board. RCA must have a good connection.


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## Vash

I have a BMW M5 with the battery in the trunk. I have all my amps ground hooked up the the negative battery terminal. I have read every single post and want to punch this thread in the face. IS IT BAD OR NOT YES OR NO???


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## 12v Electronics

Vash said:


> I have a BMW M5 with the battery in the trunk. I have all my amps ground hooked up the the negative battery terminal. I have read every single post and want to punch this thread in the face. IS IT BAD OR NOT YES OR NO???


Chad is correct that is could be bad. In fact very bad. Even though the chances of this happening are slim, grounding it to the chassis would be preferred. Not only for the damage possible but noise as well. There are many good chassis grounding points in an M5 in the trunk. Remove one of the trunk side panels and you will find a bunch of factory ground points. They usually have a connector with brown wires attached into a flat cluster connector to a ground nut. These are usually the places you want to go to in your car.


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## Vash

12v Electronics said:


> Chad is correct that is could be bad. In fact very bad. Even though the chances of this happening are slim, grounding it to the chassis would be preferred. Not only for the damage possible but noise as well. There are many good chassis grounding points in an M5 in the trunk. Remove one of the trunk side panels and you will find a bunch of factory ground points. They usually have a connector with brown wires attached into a flat cluster connector to a ground nut. These are usually the places you want to go to in your car.


I know where exactly you're talking about. Thanks!!!!!!!


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## chad

12v Electronics said:


> Am I blue in the face yet?


Not yet 



12v Electronics said:


> Chad is correct that is could be bad. In fact very bad. Even though the chances of this happening are slim, grounding it to the chassis would be preferred. Not only for the damage possible but noise as well. There are many good chassis grounding points in an M5 in the trunk. Remove one of the trunk side panels and you will find a bunch of factory ground points. They usually have a connector with brown wires attached into a flat cluster connector to a ground nut. These are usually the places you want to go to in your car.



But that pretty much sums up the questions.


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## benny z

i am in process of the amp installs in my 5-series. the red circle here indicates the point i ended up using for my ground. in my previous install i had grounded directly to the battery (batt is in trunk...), but after reading this thread (great timing!) i opted not to do that this time. i simply sanded this spot down to bare metal, drilled a hole for a 5/16 bolt, and slapped the grounds to it. this made for a short ground run to the amps right in front of it.










(here is the 1st of 3 amps installed - the ground is right up behind the hole where the power wires for the other two amps are coming through.)


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## psychotic

All I will say is that a car is a floating DC system, and floating DC systems have no ground.... They have a conductor refered to as ground, which is the same as a flattened wire, aka the chassis/frame

the rest you can argue with other Electrical Engineers over at our forum:
http://cr4.globalspec.com/


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## SQ4ME2

GlasSman said:


> Why would you want to make a *WORLD TOUR* like that tying the HU and AMP ground?
> 
> THats a ground loop and inducted noise *WAITING* to happen.
> 
> If you need to ground the HU theres always a section of metal behind the dash with an existing star washer and nut/bolt near the HU.
> 
> If there isn't one drill it yourself.


i agree with Glassman, and BMW cars have noise issues anyway


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## chad

psychotic said:


> All I will say is that a car is a floating DC system, and floating DC systems have no ground.... They have a conductor refered to as ground, which is the same as a flattened wire, aka the chassis/frame


Can of worms opening in 5, 4, 3, 2..........

Well done and well said.


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## danssoslow

psychotic said:


> When you say you look at the ground as a point of 0v reference, and the chassis as a conductor as is any ground system, key word being system, aka part of a circuit.... the 0v reference is known as a "SAFETY GROUND", which would be found in the electrical wiring of a home...
> picture:
> positve slot, negative slot, and below and between the two, a circular "ground"
> 
> Now how can this make sense if the Neg. is supposed to be the ground???
> 
> Well, to clarify this dicussion I think it would help if we clear up the terms we are talking about...
> 
> **NEGATIVE GROUND / CAR GROUND / CHASSIS GROUND: a large conductor connected to the negative of a circuit (ex: car chassis connected to the negative battery terminal)
> 
> **SAFETY GROUND / 0V GROUND: a ground that does not conduct any current. It is usually run to the ground (read: earth, dirt, 0volts) (Ex: the 3rd wire on an electrical 'main') This type of ground is a safety percaution to guide high voltage current away from other electrical equipment and people, as well as cause fuses/circuit breakers to stop the current flow. It is also used to protect sensitve currents from interference.
> 
> **POSITIVE GROUND: If you are working on an old tractor, or a car that is made prior to the 60s


To add; in an AC circuit, what you are referring to as the "negative ground" is technically called a grounded conductor. This conductor is generally referred to as a "neutral"; but that is actually only the case when the conductor is carrying the load of every phase within the circuit. Grounded is the right name.

What is commonly referred to as the "ground" is technically called a grounding conductor.

As you have pointed our with the automobiles, they are both grounds and are common. Where they are separate is in their utility; as one is carrying the loads of all devices (grounded), and one is their to provide a high(er) potential circuit path in case of a circuit fault (grounding).

The Earth itself is actually a conductor in an AC circuit; as electricity isn't simply looking to find itself in the dirt, but completing the circuit back to the source, the power plant.


Taking this back into the car, it's safe to just drop the word ground altogether and call it what it is, a common; a conductor back to the original source. It would certainly makes sense; especially when considering "positive ground" circuits as it isn't "grounding out" the positive, the chassis and frame are common to the positive side of the circuit. Where the car differs is in that most all of the circuits use the chassis as its sole conductor back to source; therefore combining the grounded and grounding conductor. This would also explain the 0V situation; as going from the negative terminal to the chassis is a common. If you go into your house panel and read the voltage between the two top breakers, left and right, will read 0V, as there are common being on the same phase; but the breakers are still hot.

This would also make the necessity for fusing the negative wires, as explained by Chad, in an automobile easier to understand for those who do not believe it is necessary. As explained in the AC circuit, the negative in each electrical device and the chassis are in common; as they are both conductors to complete the circuit back to the power source. Running directly to the battery has now made it a GROUNDED conductor as in an AC circuit, separating itself from the chassis (GROUNDING) to become a second possible path back to the source, but still common. Beings that they are in common, if one does break, the other will carry the load.

In closing, I declare from now on we drop the word ground from automotive circuitry, and refer to the chassis and frame as the common conductor; and the act of "grounding" as bonding. A Negative Common we will call it.

Screw the spoon! In the car.... there is no ground!:bigthumb:

/stupid rant


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## theothermike

new scenario arises for my diyma friends.

I had a kinetik 1800 under hood and 2400 in the back. it recommended a 0 gauge run for + and - to hook up the other in parallel for the wattage i was running at the time. Keep in mind i have done big 3 with 0 gauge already as well.

I still have that run. and i was going to use that run and just connect a kicker distro to it and then turn it into 2x 4 gauge runs + 1 0 gauge run going into the 100.2 100.4 and 1500D sundown amps im running.

it a run from my 1800 still under the hood to the back.

However i have a 94' camry, a unibody. would it be better to ground to a better spot in the back of my camry. I have a street wires 0 gauge ground block new and sitting in my tool box.

Let me know.

List of equip that would be run off the 1 run and distro - h701, 100.2, 100.4, 1500D, 7x 60mm fans.

Mike


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## chad

danssoslow said:


> In closing, I declare from now on we drop the word ground from automotive circuitry, and refer to the chassis and frame as the common conductor; and the act of "grounding" as bonding. A Negative Common we will call it.


Count me in, got room for one more on the band-wagon?


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## danssoslow

chad said:


> Count me in, got room for one more on the band-wagon?


Do I see a new team name in the signature?


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## DaleCarter

My car IS grounded to the f-ing GROUND! I know cuz i got two of them little straps what hangs down and touches the ground so i don't blow my ass up at the gas station from all the static electricity my tires make rubbin gon the ground. Don't believe me? Rub on a balloon and watch yer hair stand up, same thing!.

My granddaddy taught me that strappy thing trick right after he taught me to pull all that fuzzy **** out the mufflers to make 'em sound bitchin' and get the truck to haul some real ass.


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## chad

DaleCarter said:


> My car IS grounded to the f-ing GROUND! I know cuz i got two of them little straps what hangs down and touches the ground so i don't blow my ass up at the gas station from all the static electricity my tires make rubbin gon the ground. Don't believe me? Rub on a balloon and watch yer hair stand up, same thing!.
> 
> My granddaddy taught me that strappy thing trick right after he taught me to pull all that fuzzy **** out the mufflers to make 'em sound bitchin' and get the truck to haul some real ass.


I just use my curb feelers


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## danssoslow

DaleCarter said:


> My car IS grounded to the f-ing GROUND! I know cuz i got two of them little straps what hangs down and touches the ground so i don't blow my ass up at the gas station from all the static electricity my tires make rubbin gon the ground. Don't believe me? Rub on a balloon and watch yer hair stand up, same thing!.
> 
> My granddaddy taught me that strappy thing trick right after he taught me to pull all that fuzzy **** out the mufflers to make 'em sound bitchin' and get the truck to haul some real ass.


Oh, I believe you... I believe you. 



chad said:


> I just use my curb feelers


Do donks use antennas for curb feelers? Those gold ones with the swirl in the middle would be stunnin'... Icy Hott Stunnin'!


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## psychotic

interesting. 
I used to run one of my systems with the amp's neg cable through a gromit in the bottom of the trunk. It worked pretty good until you got up to highway speeds, and then the wind would break the connection.


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## theothermike

can someone answer my question in the last page. because my cars a unibody does it make a difference?


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## Attack eagle

no, unibody or chassis on frame makes no difference.

I hope you are running an isolator and have all your audio gear on one battery (including the head), especially since you are running completely dissimilar batteries in parallel.
Or did i misunderstand and you are ditching the second battery?


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## theothermike

the second battery is gone. i just have the 1800 up front. but both batteries were the same brand and type.

so ur saying, unibody, chasis / frame. it makes no difference i should still ground in the back and not use the negative run to the battery?

any other people agree.

i mean i still do have an upgraded big three ground. would it make a difference.


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## Attack eagle

correct. why restrict it down to a 15- 20 foot 0 gauge wire both ways when you have an entire car as a conductor? not to mention the space and hassle and expense.


My car has a rear battery OEM, it is connected to chassis on the negative side, with a positive lead that runs up front to a jump point and then on to the alternator. Every other car I've ever owned or worked on with factory rear batteries have been the same re negative, though some (british) weren't nice enough to supply an underhood jump point .


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## theothermike

how big of a difference would it make if i didnt want to ground my amps to the body in the back and do what i was going to do. since the ground run is already ran, cable clamped under carpet, etc...

i mean is a there gonna be a difference especially if i already upgraded the negative to chassis ground with another 0 gauge run as well?


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## theothermike

anybody. this is a rather important thing seeing how im going ib, and if i seal it up then i screwed, can a few more heads chime in about the differences, and result using my variables


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## 12v Electronics

Ground it to the chassis. Period.


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## psychotic

ground it to the chassis, or run 3 more ground wires to your engine block, and 2 more to the chassis.... then you should be safe from frying your equipment?


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## therapture

12v Electronics said:


> Ground it to the chassis. Period.


While I may not be much in the car audio world, I have been in the automotive repair/sales business for 20+ years, and this is correct. You would not believe some of the damage I have seen from people incorrectly installing amps and what not...


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## attil379

What can i use as a ground if im hooking up a system in my garage?


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