# Grounding multiple amps



## anon_az (Dec 13, 2005)

When installing two or more amps, is it better to give each amp its own ground point or should they all converge into one ground cable / mounting point? I've always thought it was better to run power to a distribution block, but ground each amp individually. I was looking for some insight as to what the best method is. Thanks. :beer:


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## Pat @ Pitt Soundworks (Nov 14, 2008)

I ground them all to the same place.


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## mainelyr32 (Sep 27, 2010)

Depends on the watts total. You can do it up to a 2 awg to a distribution block. Which would be 2 4 awg out puts, or 3 6 awg. But if you have like 3 amps each needing 4 awg or something bigger individually ground them


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## Pat @ Pitt Soundworks (Nov 14, 2008)




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## NFrazier (Jul 22, 2006)

Pat @ Pitt Soundworks said:


>


My feelings exactly.

Ground to the same spot.


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## Non_Affiliated (Feb 12, 2002)

I prefer the common tie point, but with a twist. I have 2 4 AWG wire running from my ground block to my back seat mount studs, one to each stud. They are locate next to each other about 2" apart. But like stated I wouldn't mount multiple grounds via cables in different areas.


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## BassNotes (Mar 16, 2005)

If they're next to each other, grounding them to a common point is convenient. If they're not, just ground them well to the chassis (assuming the ground connections among the battery, engine block, and chassis are all good).


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## anon_az (Dec 13, 2005)

Thanks guys!


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## NFrazier (Jul 22, 2006)

BassNotes said:


> If they're next to each other, grounding them to a common point is convenient. If they're not, just ground them well to the chassis (assuming the ground connections among the battery, engine block, and chassis are all good).


The reason most installers ground to the same point isn't for convenience.....


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## BassNotes (Mar 16, 2005)

NFrazier said:


> The reason most installers ground to the same point isn't for convenience.....


Well, it is convenient. Other than that, there's no actual reason unless your chassis is in bad shape.


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## Pat @ Pitt Soundworks (Nov 14, 2008)

The reason for same grounding locations is to reduce the chance of causing a ground loop. THAT is why.


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## BassNotes (Mar 16, 2005)

It's not necessary in a DC-powered system where the - side is the system reference and the chassis. (Unless perhaps the equipment has some bad design defects.)


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## Pat @ Pitt Soundworks (Nov 14, 2008)

Why it happens is differences in the resistance-to-ground varies between amplifiers and source units (almost always with uni-body construction) and where the ground shield on the interconnect is terminated on both amp and source chassis. This causes feedback through the interconnect shield in to the source unit. Proper interconnect shielding is done at the source unit only. 

There's also something about a floating ground which I can't remember.


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## NFrazier (Jul 22, 2006)

BassNotes said:


> Well, it is convenient. Other than that, there's no actual reason unless your chassis is in bad shape.


 HAHA, WOW! it's to reduce that chance of ground loops.


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## jmj (Feb 6, 2001)

NFrazier said:


> HAHA, WOW! it's to reduce that chance of ground loops.


 That's my understanding as well. IIRC most amplifier/active crossover installation guides (that I've read) state that all equipment should use a common ground to minimize ground loops.


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## BassNotes (Mar 16, 2005)

Pat @ Pitt Soundworks said:


> Why it happens is differences in the resistance-to-ground varies between amplifiers and source units (almost always with uni-body construction) and where the ground shield on the interconnect is terminated on both amp and source chassis. This causes feedback through the interconnect shield in to the source unit. Proper interconnect shielding is done at the source unit only.
> 
> There's also something about a floating ground which I can't remember.


 If you have two or more good connections to the car's chassis (and the chassis isn't rusting apart), the resistance through the chassis between those points will be much lower than through any ground wire (of a practical and usable gauge) that you might join them with. 

If the source unit and amp are well bonded to the chassis, there's really no advantage in breaking the interconnect shield (assuming the manufacturers terminated the input and output shield terminals properly). 

With car audio, you have multiple chassis within a chassis ground plane (the car). You can use that to your advantage.


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## BassNotes (Mar 16, 2005)

NFrazier said:


> HAHA, WOW! it's to reduce that chance of ground loops.


 See post #12.


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## Pat @ Pitt Soundworks (Nov 14, 2008)

BassNotes said:


> If you have two or more good connections to the car's chassis (and the chassis isn't rusting apart), the resistance through the chassis between those points will be much lower than through any ground wire (of a practical and usable gauge) that you might join them with.
> 
> If the source unit and amp are well bonded to the chassis, there's really no advantage in breaking the interconnect shield (assuming the manufacturers terminated the input and output shield terminals properly).
> 
> With car audio, you have multiple chassis within a chassis ground plane (the car). You can use that to your advantage.


 So you're going to argue resistance of wire over a short length playing a factor? Three or four feet of 4 gauge has only a negligible difference in resistance over 1-2ft. An ideal ground on the chassis (lets actually say frame, because grounding to the chassis is silly in a unibody car) would have no more or less resistance than the wire used to connect it to the amp. 

Also if you have the amps coming off of a distribution block and the wire is properly sized, there is no harm in running the same gauge from a ground distribution block to the frame. 

You have a whole lot of assumptions in this post, which is the exact reason we do it  

In one of the cars I've done, we ran 1/0 gauge from the front to the back battery, ground to the frame at both ends, and then amps on a distro to the back battery. On my car, I have five amps that all ground directly to their amp rack, which is then grounded through a 6" run of 2/0 gauge to the frame.


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## BassNotes (Mar 16, 2005)

Actually, "chassis" is the correct word, because unibody vehicles have no frame. 

I'm not arguing over resistance of wire. I'm just pointing out that star grounding in a car is unnecessary and offers no improvement over direct grounding to the chassis (which actually would offer lower resistance than wire, though the difference is negligible). I understand that it might be an unquestioned habit among installers. 

I didn't assume anything that isn't borne out by reality, Pat.


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## Non_Affiliated (Feb 12, 2002)

Maybe I missed something But I think you both are in agreement, just saying it in a different way. Maybe I am interpreting this wrong, but I have had many heated debates with a cousin, which it sounded like were diagreing only to realize we were saying the same thing in a different way so it seemed we disagree. 

The only issue I find in Unibody cars is that there are some frame structures have body sealer which inhibits a good ground.


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## BassNotes (Mar 16, 2005)

Non_Affiliated said:


> The only issue I find in Unibody cars is that there are some frame structures have body sealer which inhibits a good ground.


 That could be. You do need good, gas-tight metal-to-metal contact to connect a ground really well to the chassis.


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## Bugs (Aug 16, 2001)

anything I have ever read, any pro I've ever spoke to always say the same thing 
"if possible, ground all amps to same location" 

i've heard varying reasons why, but the result is always the same.


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## BassNotes (Mar 16, 2005)

It's still unnecessary to ground all amps to the same location, as long as you ground them well to the chassis.


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## LT1M21Stingray (Sep 14, 2006)

All equipment should use a common ground to minimize ground loops.


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## BassNotes (Mar 16, 2005)

Mtl-Marc said:


> All equipment should use a common ground to minimize ground loops.


 True, and the car's chassis already is a common ground. 

What you don't need is route the grounds to a single connection point on the chassis.


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## Pat @ Pitt Soundworks (Nov 14, 2008)

The problem, like Non Affiliated (and I think I) said was that not all "grounds" in the car are created equal. 

If it's the same piece of the chassis, sure. But you CAN have a difference in resistance to ground across the different pieces that make up the trunk or hatch.


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## BassNotes (Mar 16, 2005)

Pat @ Pitt Soundworks said:


> The problem, like Non Affiliated (and I think I) said was that not all "grounds" in the car are created equal.
> 
> If it's the same piece of the chassis, sure. But you CAN have a difference in resistance to ground across the different pieces that make up the trunk or hatch.


 Not the trunk itself; that is part of the chassis. A trunk lid or a hatch aren't part of the chassis, though, and you wouldn't want to rely on conductance across the hinges to make a good ground. If you have to ground something to the hatch or trunk lid, there should be an appropriate ground strap connecting it to the chassis. Same thing with doors. Even the engine block needs a ground strap to the chassis so it's not reliant on conductance through the engine mounts. 

The car's chassis is a really big, good-quality ground plane, and as long as it's intact you actually can consider it all equal. (If the chassis is rusting apart, though, that won't be true, but you'll have other bigger issues, like safety. One visual clue would be that the car is taking on a banana shape.)


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## LT1M21Stingray (Sep 14, 2006)

^^


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## NFrazier (Jul 22, 2006)

BassNotes said:


> Not the trunk itself; that is part of the chassis. A trunk lid or a hatch aren't part of the chassis, though, and you wouldn't want to rely on conductance across the hinges to make a good ground. If you have to ground something to the hatch or trunk lid, there should be an appropriate ground strap connecting it to the chassis. Same thing with doors. Even the engine block needs a ground strap to the chassis so it's not reliant on conductance through the engine mounts.
> 
> The car's chassis is a really big, good-quality ground plane, and as long as it's intact you actually can consider it all equal. (If the chassis is rusting apart, though, that won't be true, but you'll have other bigger issues, like safety. One visual clue would be that the car is taking on a banana shape.)


 Not all cars are like that though. For instance my car's "rear parcel shelf" it attached to the chassis, one piece, but it's resistance and ground path is different from say the spare tire well. It's also a different metal, with different conductivity...


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## Pat @ Pitt Soundworks (Nov 14, 2008)

BassNotes said:


> The car's chassis is a really big, good-quality ground plane, and *as long as it's intact* you actually can consider it all equal. (If the chassis is rusting apart, though, that won't be true, but you'll have other bigger issues, like safety. One visual clue would be that the car is taking on a banana shape.)


 We're not talking about grounding through hinges. I highlighted the assumption that you're making (what we're arguing here). And here, again, is the reason 



Non_Affiliated said:


> The only issue I find in Unibody cars is that there are some frame structures have body sealer which inhibits a good ground.


 Or paint, or are only held in contact with glue.


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## BassNotes (Mar 16, 2005)

Pat @ Pitt Soundworks said:


> We're not talking about grounding through hinges. I highlighted the assumption that you're making (what we're arguing here). And here, again, is the reason.


 I don't know what assumption that is. I did say that if the chassis is not intact--i.e., rusting apart, breaking up, etc.--then your issues are much greater than grounding of audio equipment. Then you've got more important structural safety issues that ground wires just won't solve.


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## BassNotes (Mar 16, 2005)

NFrazier said:


> Not all cars are like that though. For instance my car's "rear parcel shelf" it attached to the chassis, one piece, but it's resistance and ground path is different from say the spare tire well. It's also a different metal, with different conductivity...


 Things that are attached to the chassis, like doors, hatches, seats--and in your car, a parcel shelf--are not part of the chassis. If you ground something to them, you'll also need a ground strap to the chassis, and it won't necessarily be as good and reliable as grounding directly to the chassis--even if you run wires all to one point.


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## BassNotes (Mar 16, 2005)

Mtl-Marc said:


>


 That's one of my all-time favorite cartoons.


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## Pat @ Pitt Soundworks (Nov 14, 2008)

Car's aren't built looking like delorians, then painted and sealed. 

I think it's time for this :banghead: 



> Things that are attached to the chassis, like doors, hatches, seats--and in your car, a parcel shelf--are not part of the chassis. If you ground something to them, you'll also need a ground strap to the chassis, and it won't necessarily be as good and reliable as grounding directly to the chassis--even if you run wires all to one point.


 So what you're saying is you want to argue the definition of chassis. I thought this much was already assumed :facepalm:


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## BassNotes (Mar 16, 2005)

Pat @ Pitt Soundworks said:


> So what you're saying is you want to argue the definition of chassis. I thought this much was already assumed :facepalm:


 No, I'm not arguing definitions. I honestly thought just about everyone knew what "chassis" means, but it seems that some believe it includes items that are peripherally attached to the chassis. I'm sorry for the confusion.


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## NFrazier (Jul 22, 2006)

BassNotes said:


> Things that are attached to the chassis, like doors, hatches, seats--and in your car, a parcel shelf--are not part of the chassis. If you ground something to them, you'll also need a ground strap to the chassis, and it won't necessarily be as good and reliable as grounding directly to the chassis--even if you run wires all to one point.


The rear parcel shelf if not attached to the chassis, it is part of the chassis, go rip a mk4 jetta apart. it is welded to the unibody.


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## BassNotes (Mar 16, 2005)

NFrazier said:


> The rear parcel shelf if not attached to the chassis, it is part of the chassis, go rip a mk4 jetta apart. it is welded to the unibody.


In an earlier post you said it was attached to the chassis but not a part of it. I was going by your description.

Thanks for correcting your information.


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