# grounding to frame/chassis vs. grounding direct from battery



## Jroo (May 24, 2006)

Is there any advantage to either? In my case I only have the single battery up front. I am going to do the Big 3 with 1/0 and will finally lay cables to the rear to start the system when it warms up. My power wire is 1/0 so I know my ground should also be 1/0. On a smaller set up and a car without a second batter, is grounding from the battery just overkill? Just wondering as I see it most with megawatt systems and strictly SPL guys. Anything that I should worry about or tips if I do decide to ground directly from the battery?


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## minbari (Mar 3, 2011)

its not going hurt anything but your wallet to make run to the battery for ground.

not alot of advantage most of the time though. the car is made of mostly metal and will have alot more current carrying capability than a dedicated ground run. just make sure you ground in a good location.


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## Randyman... (Oct 7, 2012)

Agreed


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## Kevin Kessler (Dec 17, 2012)

The thin Sheetmetal of a unibody car is only equivalent to around a 4 gauge wire. Plus you never know what the path of current is going to be, it might be jumping around Through 15 different spot welds on the way back To your amplifiers. Copper is a much better conductor of electricity than steel. I don't think anyone here would run a power wire made of steel back to their amplifiers so why would you want to use a ground Made of steel? So anyway any install that has current requirements Of 4 gauge or less A ground in the Sheetmetal should be fine anything above I would run a ground from the battery back.


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## boogeyman (Jul 1, 2008)

i would ground to the frame.Keeping the ground as short as possible


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## GS-R_Autotech (Oct 3, 2011)

What is your source when you say body grounding is equivalent to a 4awg ground???


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## Kevin Kessler (Dec 17, 2012)

I was told this by a tech\engineer from JL audio that said he had run some tests on the Current capacity of the sheet metal In unibody cars. It makes sense to me so I'll have to believe it unless proven otherwise.


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## ErinH (Feb 14, 2007)

my advice, based on a recent experience...

I had my grounds shared at one point on the frame. I had induced noise from the A/C motor because, even though the point wasn't shared, the path was. I've had this noise for a couple years now but it's been manageable. I finally got around to testing some things out and found a single 4g run to the battery solved the problem entirely. Took 15 minutes to run the wire and hook everything up and now the electrical noise I couldn't get rid of is gone.

Go battery if you can.


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## Kevin Kessler (Dec 17, 2012)

I have also seen a vary Noticeable improvement in voltage drop With cars that relied on a body ground for the amps after I ran a zero gauge ground back to the amplifiers


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## ZAKOH (Nov 26, 2010)

I gut feeling is that car body is a better conductor than a 4awg wire, but it can introduce some noise. I wonder, would running a long 4awg ground cable to the battery result in a significant voltage drop? Would it be better to use a thicker wire?


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## NA$TY-TA (Mar 25, 2009)

Hmm. I've never here the dram sheet metal = 4 gauge before.... I'd like to see real world tests to prove this since I'd like to think 95% ground to sheet metal vs running a dedicated ground wire back to the battery.


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## bassace (Oct 31, 2011)

Kevin Kessler said:


> it might be jumping around Through 15 different spot welds on the way back To your amplifiers.


This is what I am very curious about. :thinking2:


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## Justin Zazzi (May 28, 2012)

Kevin Kessler said:


> The thin Sheetmetal of a unibody car is only equivalent to around a 4 gauge wire. Plus you never know what the path of current is going to be, it might be jumping around Through 15 different spot welds on the way back To your amplifiers. Copper is a much better conductor of electricity than steel. I don't think anyone here would run a power wire made of steel back to their amplifiers so why would you want to use a ground Made of steel? So anyway any install that has current requirements Of 4 gauge or less A ground in the Sheetmetal should be fine anything above I would run a ground from the battery back.


Complete and utter nonsense.

Within the scope of electrical resistance and not considering noise, lets work this out using a 10 gauge sheet metal unibody vs 0 gauge copper wire. Some numbers are being rounded off for simplicity, but will not greatly effect the outcome.

Steel has a resistance of up to 10x that of copper (assuming absolute crazy worst case scenario here). To have equivalent resistance between the battery ground and your equipment ground, the cross sectional area of the steel has to be about 10x the cross sectional area of the copper, and the total path length has to be similar. Lets assume a really terrible scenario in that the path through the steel in the unibody is double the path length of a copper wire run.

A 0 gauge copper wire should have a diameter of 0.325", or a cross sectional area of 0.083 square inches. 10 gauge steel is about 0.135" thick, but as shown above we need about 10x as much of it. So:

(0.135" thick steel) * (steel width) / 10 = 0.083 square inches of copper

Solve for the width and you get roughly 6 inches of width. But we need to compensate for a imaginary path roughly double that of the copper wire, so this width needs to double to compensate.

So in an ideal world, just a 12" wide strip of 10 gauge sheet metal will have the same resistance as a single 0 gauge run of copper wire. There are a few things in the real world that would be different such as intermediate welds and so forth, but when you think about it, these are not deal-breakers.

If you can demonstrate otherwise, I would love to see and read what you come up with.

-J

edit: After reading what I wrote above, it sounds more abrasive than I meant. I don't mean to attack you Kevin, or anyone else. I do hope the content is useful though.


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## Chaos (Oct 27, 2005)

There are valid points to be made either way.

For 95% of applications, grounding through the body is perfectly fine. For super-high current (SPL) applications, grounding through the frame may be more effective. 

In rare cases however, such as what bikinpunk describes, running a dedicated wire to complete the circuit just works and/or makes the most sense.



Bottom line: Don't over-think it. If you are running around 1kW of dynamic power on a daily basis and you have no noise in the system, just leave your ground alone.


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## Kevin Kessler (Dec 17, 2012)

Jazzi No offense taken. I was pretty much just Quoting back Word for Word what the JL audio tech had told me 5 years ago And he said he did some real world testing. It looks like you Have a background in engineering so on paper with all the facts I'm sure it does look like nonsense And I can't argue that but like I said With A.B. comparisons in customers cars and even in my own vehicle I have seen improvement in voltage drop with a ground run to the Battery. Please do not mistake anything I've said as fact It is only an observation I've made and I'm sure there are many many variables. Like someone said in the beginning of the post only thing running a ground to the battery is going to hurt is your wallet


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## Jroo (May 24, 2006)

Im finally getting around to installing all the equipment in my Volvo V70 over to my 04 Pathfinder. I asked since I was going to lay cable soon, I figured I would just do it right one time and leave it. Basically my system is 3 amps(JL 300/2, JL 300/4, and RF 800A2). On paper my rms rating should be 1400 watts. I am using 1/0 IXOS cable for everything including big 3. My volvo was grounded in the hatch and then run to a street wires fuse block that has power in ground all in one(cant remember the model number). Again, it wasnt an issue before, but didnt know if I gained anything by going from the battery.


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## chad (Jun 30, 2005)

if you go to the battery with anything but the frame... you fuse it.... and not for the wire but for the gear and hope your ass off that it's less than the starter can pull in less than the time it takes to pop bubblegum.

If you don't and you, for some reason, lose the frame ground and your gear ground is the only thing left, all ****ing hell of sorcery will develop. And leave a hell of a dent in your wallet.

"Grounding" to the battery is just a VERY VERY poor idea. And before ANYONE says it's not name one facet of anything electrical that actually recommends this approach.

The car battery negative is NOT GROUND.


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## minbari (Mar 3, 2011)

cajunner said:


> the sheet metal might be 16 gauge, at best unless you drive a Land Rover.
> 
> *the spot welds, may be all that exist to pass this current through, as the entirety of the sheet metal isn't being used, it's only being used at the contact points of weld.*
> 
> I am also completely in the camp of using either a frame rail for those cars with frames, and running separate ground in uni-body styles for current draw estimates over 60 amps on test tones at 0 db, or 80 amps on music (basically 75% of fuse ratings added up) or, that may be backwards. Anything over 100 amps at the fuse could use a separate ground, imho.


what about the fuses themselves? you have an 1/8" contact patch for current to flow through and you pull 50-100 amps through it just fine. if you have a dozen or more spot welds in the ground path, you certainly have enough. The rest of the body acts as the conductor.

copper : (20 °C) 16.78 nΩ·m
steel: (20 °C) 143 nΩ·m

does it really matter?


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## Kevin Kessler (Dec 17, 2012)

There are a lot of valid points being made here not sure what to believe anymore? Like I said I have seen a improvement in voltage drop with running a ground the battery


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## cubdenno (Nov 10, 2007)

I ran a dedicated negative run from the battery to the trunk. 2006 Toyota Solara. I regained almost a volt at the back. Interior lights became brighter, tail lights became brighter. Initially I just used the dedicated negative run for the electronics. After a stern lecture from Chad,  , Who pointed out what he mentions above, I changed the configuration. I tied the dedicated run to the chassis at 3 points. Where the battery was connected up front, in the car interior under the seat and at the initial grounding point in the trunk where my ground distribution is tied to. It made a difference that was visibly noticeable. As well as measurable. It didn't break my wallet as I used Knu oversized 1/0 CCA. 

The nice thing is, it is an easy check to see if it will help. Get a length that runs front to rear outside the vehicle and just take some measurements with and without at various volume levels. See if there is voltage drop with and without. Is there noise? Is there less noise? 

While yes sheet metal of a body should have enough current carrying capacity to be enough, it also has more resistance,Add in that as the metals heat up, the steel will have even more resistance. Add in that the steel used is high carbon (usually) and can have inperfections in the chemistry at different points that may not cause a weakness but certainly can affect shortest path. There is another affect called drift or something that is based on the geometry of the conductor. Can't remember the exact term.

Now does all that mean using the steel body as the negative run from the battery is bad? In almost all circumstances in a vehicle probably not. But add in high current usage audio equipment and the perpetual pursuit of sonic nirvana or the output equivelent of a bomb, and then maybe, it's not. 

That's why I tried what I did and it worked for me. Your vehicle/install may not need it.


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## 14642 (May 19, 2008)

Everything in the car including the head unit is connected to the chassis at various points. The alternator and the battery are as well. Chasing your ground connections to break noise causing ground loops is valid but often a bigger PITA than is necessary. The Loop that causes noise is a difference between ground and audio ground in one or more of your pieces of equipment. Circuits that eliminate the common connection between audio ground and chassis ground are much better solutions for ridding the car of noise. 

The SPL guys don't give a hoot about noise. They care that they're getting every last ampere of current to their amplifiers. Unless you're running your system full bore, a few milliamps of drop doesn't matter if you don't have noise.

Just ground to the sheet metal.


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## Sulley (Dec 8, 2008)

I had some serious noise issues in my 04 Civic sedan, ran another 4ga run from the ground distro block, back to the battery. It deff cleaned most, if not all of it up. 

Got a 4 door Jeep Wrangler now, grounded to the sheet metal behind the rear seats. DEAD silent, almost unbelievable. Only noise when my system is on now is that god damn fan in the ARC KS300.4 amp.

It's vehicle dependent. If you have no system noise, ground to sheet metal. 

Chad's comment really made me think tho...


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## HTX (Aug 7, 2007)

more $$$


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## Justin Zazzi (May 28, 2012)

chad said:


> if you go to the battery with anything but the frame... you fuse it.... and not for the wire but for the gear and hope your ass off that it's less than the starter can pull in less than the time it takes to pop bubblegum.
> 
> If you don't and you, for some reason, lose the frame ground and your gear ground is the only thing left, all ****ing hell of sorcery will develop. And leave a hell of a dent in your wallet.
> 
> ...


Chad,

I could be wrong (so help me understand if I am), but none of what you claim makes any sense.

Please be more specific in how this kind of failure will cause "all ****ing hell of sorcery" to develop. I do not see it.

Also, please explain what benefit you would have fusing any sort of ground leads.

Lastly, explain how a battery's negative terminal _is not ground_. If that were true, why have car companies connected the started motor relay to both the positive _and negative battery terminals_ for ages?

-J


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## Kevin Kessler (Dec 17, 2012)

What chad said makes sense Although I think it's a longshot the situation would ever happen but it could. He is talking about if Somehow you lose your factory body ground the next place that ground would pull from if you tried to start your car is your dedicated Ground wire run back to amplifiers which then would pull ground Through Your RCA cables from your head unit and That would definitely burn some stuff up Pulling 200 Amps through that ground path to start your car. When I Run a dedicated ground to the amps in a vehicle I wire up 2 short body grounds in the engine compartment to the battery to have a failsafe so this situation should not happen. Can't explain how the batteries Negative terminal is not a ground it's about the best place I can think of for a ground if you're pulling some Amperage?


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## Wy2quiet (Jun 29, 2010)

Kevin Kessler said:


> What chad said makes sense Although I think it's a longshot the situation would ever happen but it could. He is talking about if Somehow you lose your factory body ground the next place that ground would pull from if you tried to start your car is your dedicated Ground wire run back to amplifiers which then would pull ground Through Your RCA cables from your head unit and That would definitely burn some stuff up Pulling 200 Amps through that ground path to start your car. When I Run a dedicated ground to the amps in a vehicle I wire up 2 short body grounds in the engine compartment to the battery to have a failsafe so this situation should not happen. Can't explain how the batteries Negative terminal is not a ground it's about the best place I can think of for a ground if you're pulling some Amperage?


I have noise using the body grounds on my Protege. I think this summer I will probably run a dedicated 1/0 to the trunk. The idea that the ground would fail and destroy your entire sound system is like saying don't step outside, or you will be struck my lightning.

I mean virtually all of us here are running ground upgrades, and I personally have a 0 gauge from my battery to the shock tower. I don't see this failing, plus the stock ground, and then drawing from the amplifier instead. In my case running a PC, I don't use an H/U running the stock ground, so I could run everything to the 1/0 (which I would also chassis ground along with the battery).


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## Sine Swept (Sep 3, 2010)

I too use a 1/0 pos and neg to distroblocks in the rear. ( I did hang with SPL guys)

Its the current carrying abilities I'm after, plain and simple.

My bigger thought is this - 1/0 CCA, seems like an oxymoron.


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## minbari (Mar 3, 2011)

Sine Swept said:


> I too use a 1/0 pos and neg to distroblocks in the rear. ( I did hang with SPL guys)
> 
> Its the current carrying abilities I'm after, plain and simple.
> 
> My bigger thought is this - 1/0 CCA, seems like an oxymoron.



Why? CCA 1/0 don't carry as much as copper, but it is still a good conductor
Sent from my motorola electrify using digital farts


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## Danometal (Nov 16, 2009)

I have a 1/0 direct ground from my amp rack in the trunk to the battery up front, but it makes a quick pit stop at the chassis about a foot from the battery before continuing on to the neg battery terminal. Zero noise for me, and it has helped to sustain my voltage considerably (my car may have a lot of epoxied panels and spot welds).


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## evo9 (Jul 6, 2005)

chad said:


> if you go to the battery with anything but the frame... you fuse it.... and not for the wire but for the gear and hope your ass off that it's less than the starter can pull in less than the time it takes to pop bubblegum.
> 
> If you don't and you, for some reason, lose the frame ground and your gear ground is the only thing left, all ****ing hell of sorcery will develop. And leave a hell of a dent in your wallet.
> 
> ...



Total rubbish!! As long as there is a correct fuse in the circuit "positive side" the system is protected. One path of least resistance is need to protect the circuit. Hence the saying, a chain is as strong as its weakest link.

As for the original question................ Personally I go directly to the battery. Why?? My 30 plus years as a certified heavy equipment automotive tech made me wise on that. As pointed out already, each body panel is connect via spot weld. In some non critical areas, a strong sealant like sikaflex is used to bond each panel with very little spot weld. If you can afford the extra cost of the wire, do it.


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## Hanatsu (Nov 9, 2010)

My amps are connected by 2x 0gauge to the battery directly - Then 3x 0gauge from the battery to chassis. Never had ground issues... ^^

Sent from my Samsung Galaxy 3 via Tapatalk.


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## TheBlindMan (Feb 7, 2013)

evo9 said:


> Total rubbish!! As long as there is a correct fuse in the circuit "positive side" the system is protected. One path of least resistance is need to protect the circuit. Hence the saying, a chain is as strong as its weakest link.
> 
> As for the original question................ Personally I go directly to the battery. Why?? My 30 plus years as a certified heavy equipment automotive tech made me wise on that. As pointed out already, each body panel is connect via spot weld. In some non critical areas, a strong sealant like sikaflex is used to bond each panel with very little spot weld. If you can afford the extra cost of the wire, do it.




What if... The vehicle is a SUV? Would the results be the same if I make a whole somewhere in the rear to get the ground wire direct to the frame? Would save lots of wire if that would work. I can imagine it would, but I'm no expert.


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## Oliver (Jun 25, 2007)

evo9 said:


> Total rubbish!! As for the original question................ Personally I go directly to the battery. Why?? My 30 plus years as a certified heavy equipment automotive tech made me wise on that.





TheBlindMan said:


> What if... The vehicle is a SUV? Would the results be the same if I make a whole somewhere in the rear to get the ground wire direct to the frame? Would save lots of wire if that would work. I can imagine it would, but I'm no expert.


Go to the frame, I've had a block of metal machined then tapped as a grounding block. THINK circuit(circle) !

The ground should be as large or larger as the power lead(voltage or power is used at the device, current needs to return to source ~ unless something has changed since Tesla and Bell)


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## chad (Jun 30, 2005)

evo9 said:


> Total rubbish!! As long as there is a correct fuse in the circuit "positive side" the system is protected. One path of least resistance is need to protect the circuit. Hence the saying, a chain is as strong as its weakest link.
> 
> As for the original question................ Personally I go directly to the battery. Why?? My 30 plus years as a certified heavy equipment automotive tech made me wise on that. As pointed out already, each body panel is connect via spot weld. In some non critical areas, a strong sealant like sikaflex is used to bond each panel with very little spot weld. If you can afford the extra cost of the wire, do it.


Really, so this is why it is REQUIRED that all emergency vehicles that run their communications to the negative battery terminal be fused, also why every single ham radio sold that was interned to be hooked directly to the battery has the negative line fused? The car audio world ain't the only world and the negative battery terminal is not ground, no matter how much you think it is.

How does that positive side fuse protect the second ground path when the original one becomes NOT the path of least resistance?

30 years huh?


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## Kevin Kessler (Dec 17, 2012)

In the unlikely event that you did lose your original first ground And the path of least resistance became your dedicated Ground to your amplifiers a fuse on the positive wire or the negative wires would not help in the situation because they would not be the weakest link in the circuit the weakest link in the circuit would be the ground traces in your head unit ,processors, amplifier or signal cables. If you're going to run a dedicated ground to your amplifiers have some failsafes built in, either ground the dedicated run once upfront or once in the back or run a couple extra short grounds from the battery.


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## chad (Jun 30, 2005)

It's not always about loss, just degradation of the original can cause significant current flow.

Although this is not as excessive, think proper lightning protection.


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## Oliver (Jun 25, 2007)

chad said:


> 30 years huh?


*LOL * :laugh:

5 yrs in the dark isn't long enough for some.


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## evo9 (Jul 6, 2005)

chad said:


> 30 years huh?





Oliver said:


> *LOL * :laugh:
> 
> 5 yrs in the dark isn't long enough for some.










*Better than substance abuse addicts & felons...*



.


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## chad (Jun 30, 2005)

Unless you are Keith Richards


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## MikeT1982 (Jul 6, 2011)

Hey guys, back 90's I began with sheet metal grounds, both upfront and in the rear (batt upfront I top of the factory ground, amp to metal in back with washers for more contact. Then I added a dedicated run just as Precision Power rcomended in their manuals back then. I bet this is the same JL tech that likes the dedicated runs, didn't JL get some of the old art series crew? Also I like to leave chassis ground! So I say use deicated and chassis both!! Also if we're pulling from a battery bank in the back....and only one alt and batt upfront the main draw is between the back batts and the amps back there (one or a couple per amp) and much less draw from front to rear, maybe 300amps of alternator but hopefully your rear bank is stiff enough for that to not happen anyways! Multiple alternators now that'd be different but then I'd say multiple chassis and dedicated runs, use whatever means you have to get those amperes of electrons back there!  I actually chose to run triple 4 gauge power and triple 4 gauge grounds and single chassis ground when I was running 4 MMATS D300HC's on a pair of DD9515's in my neons wall. The reason I ran 4 was so I could hide under carpet. I switched to single 00 gauge power and ground and chassis and everything seemed to stay the same. 190 amp stinger alt optima upfront, 4 Optimus in back. I was mid 150's at 45hZ and still same after the 0 gauge switch over. Truth be told I like the triple smaller runs. When fluking the rear batts vs the front the voltage was the same for both. No noise etc running both. I couldn't decide so chose both lol . This is just my experiences and now you guys are pulling a sh*t ton more amps with the SA amps and all your new stuff!! I am an oldschool guy at heart but would love new school and oldschool vehicles  wish I had that kind of money!


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## chad (Jun 30, 2005)

Why not star ground the whole works in back with a bigass block tied firmly to the sheetmetal THEN run the firehose to the negative battery terminal? Best of both worlds, you get your path of least resistance, safety, AND the thrill of running another wire! Tying it to sheet metal in the back will not RAISE the resistance, in fact it can ONLY lower it.


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## MikeT1982 (Jul 6, 2011)

LoL right on man


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## ZAKOH (Nov 26, 2010)

I enjoy following debates in home and car audio (e.g. "Class A/B vs Class D SQ", damping factor, crossover frequencies, 2.1 vs 5.1 sound, etc). Some never seem to end, and if you search enough then for every subject you will find highly respected posters giving completely opposing views.

Personally, I would ground every piece of the audio equipment to car body with a nice, clean solid wire and connection (the battery, the alternator, head unit, and all amps). If this doesn't work and the noise still persists, then I will run the amp ground wire all the way to the battery.


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