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Discussion Starter · #1 ·
Intro/info:

Behind this kinda desperate thread topic, lies the result of internet's plethora of information/disinformation which one can read. I've now read and heard so many different things and contradictions, that I'm lost.

Unfortunately, the car audio scene in my country, is a very small scene and the one forum that exists are full of (empty of) kids with no real knowledge. The few more competing guys are "hiding" and no one can tell me where. And, the most frustrating part is that the official agent for the brands I use, doesn't know the brands good enough to answer my questions about them.

I'm in the beginning of small SQ attempt. Never done anything other than a pair of 12" Cerwin‑Vega Strokers hooked up to a Denon, in my teens.

I'm trying to do things as right as possible the first time now, regarding power, ground and signal.

The system consists of Gladen components driven from a Mosconi D class amp with DSP (The D2 100.4 DSP).

The sub is not yet bought, neither is it's amp. It's gonna be a 10" Gladen unit driven by a bridged 2 ch Mosconi or Gladen amp.

Source is speaker out to RCA in from a 4 years old Kenwood nav/CD unit and BT via phone and plug-in module in the Mosconi.

The fronts' amp is located in/under the dash. The sub's amp will be sitting in the back. It will be fed signal from the DSP via a SI6220 Stinger 6000 Series Interconnect 2 channel 20ft cable.

The power/ground cables are OFC cables in appropriate thickness.

The car is an old mk4 Golf R32.

Questions:

My plan was to hook things up as follows: Power AND ground from the battery through the firewall and ending in two distribution blocks and from there splitting to front amp in the front and later, to the sub amp in the rear.

This was because I read that different grounding points could give ground loops. But, that is probably not that kinda ground, but the audio ground. The difference is somewhat unclear to me.

Then I read that the ground should be kept short because of loss of voltage because of the resistance in such a long cable and I could end up with the amplifier's circuit board having a different ground compared to the chassis of my car.

I also wanted to bring these three units together at the distribution block, but more amps on the same ground bolt can give amplifier ground modulation. It suddenly hit me that bringing grounding from two amps and the head unit at one distribution block, maybe could be like that. And give this ground modulation.

And don't get me started with that the whole car is full of contaminated ground from all the other stuff in the car.

Nothing makes sense anymore. Please enlighten me.
 

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Intro/info:

Behind this kinda desperate thread topic, lies the result of internet's plethora of information/disinformation which one can read. I've now read and heard so many different things and contradictions, that I'm lost.



Nothing makes sense anymore.
Been there! ...still there...


AFAIK power grounds can all go together and signal grounds can all go together. Just don't put power and signal grounds together.
 

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I ran a dedicated ground from the battery to the trunk of my car. Voltage drop was less. interior and rear exterior lighting was brighter.

I did tie the dedicated negative run to the chassis in 3 places including in the back where the negative distro block was located.
 

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Discussion Starter · #5 ·
I ran a dedicated ground from the battery to the trunk of my car. Voltage drop was less. interior and rear exterior lighting was brighter.

I did tie the dedicated negative run to the chassis in 3 places including in the back where the negative distro block was located.
If by tie to chassis you mean actually touching, I then wonder wouldn't that create ground loops? What am I missing?
 

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The chassis of the car is connected to the negative battery. If you connect your ground to the car (as long as the connection is good, and there is a path back to the battery) you shouldn't have problems with multiple ground points. They all flow to the battery. The car is basically acting like a distribution block, as long as each point has low enough resistance it shouldn't cause ground loops. Now, cars can be tricky, and sometimes what works in theory doesn't work in practice. A seemingly good ground may not have a low resistance path back to the battery, so the current will find the path of least resistance, sometimes that ends up being through something that you don't want it to be.

I've never run a ground cable back to the battery. You can use a meter to measure the resistance from a potential ground point to the battery to see if the resistance is reasonable.
 

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Discussion Starter · #10 ·
Something just hit me. Any idea of how I'm gonna be able to have one probe at the battery in the front and one at the ground in the back? Ok, the car is a short European one, but the cables on my meter is too short. Won't extending them cause troubles for the accuracy? I mean, I'm introducing more cable.
 

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You need to extend them. If a few feet of cable is adding enough resistance to make a difference then you are using terrible, undersized cable. I would bet that even standard speaker wire could be used without adding enough resistance to throw off the reading. The inductance of a speaker (2, 4, or 8 ohms) is a lot more resistance than copper wiring. You can look up the resistivity of copper, and do some calculations to estimate how much resistance the length of wire you're using has, then subtract it from the total. This would be informative, but we're talking very low numbers.

Edit: I did the calculation for you. A 1 meter length of 8 AWG copper wire will only have a resistance of 0.2005 ohms. So, even a 1 ohm resistance is likely going to be pretty bad. You should reasonably be able to find a spot less than 1/2 ohm or less.
 

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i hate to interject some simplicity into what is not really a complicated matter. But i would guess that the vast majority of cars ground the systems in the trunk or hatch close as possible to the amps and have XERO issues.

So why not try it that way and see if you have problems? There is no magic formal...ground noise can happen when using the battery just as easily as it can happen when grounded to the chassis.
 

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It is nearly impossible *not* to create ground loops unless your entire audio signal chain uses true differential signals. As long as all individual grounds are solid (low impedance back to a common point), loops won't necessarily cause audio issues.

For power, I always wire directly to the batt+ terminal with each amp grounded directly to car chassis as short as possible. Ground points are always sanded to bare metal.

I also make sure the cases (HU, DSP, amps) are grounded to the car chassis.

I only second guess this ^^ approach if I later have noise problems that cannot be remedied with normal trouble shooting steps.
 

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i hate to interject some simplicity into what is not really a complicated matter. But i would guess that the vast majority of cars ground the systems in the trunk or hatch close as possible to the amps and have XERO issues.

So why not try it that way and see if you have problems? There is no magic formal...ground noise can happen when using the battery just as easily as it can happen when grounded to the chassis.
This is pretty simple, and will work most of the time. I've just spend too much effort finding a good spot that I don't want to do it again (then again, now that I have a good ground point, I don't have to do it again). It sucks to sand paint, buy the ring terminal that of course you don't have that fits the bolt, only to find out it's a bad spot. I've got 3 patches of sanded metal that I need to deal with to avoid future rust, haha.

You're right though, most of the time it is that simple.
 

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Discussion Starter · #15 ·
i hate to interject some simplicity into what is not really a complicated matter. But i would guess that the vast majority of cars ground the systems in the trunk or hatch close as possible to the amps and have XERO issues.

So why not try it that way and see if you have problems? There is no magic formal...ground noise can happen when using the battery just as easily as it can happen when grounded to the chassis.
Nothing wrong with simplicity. It's just that I've been reading so much the last six months and don't know what to believe anymore.

Of course I can try and see what happens, it's just that taking things apart again, is something I would like not to do. That's why I would try to get it as right as possible the first time. It's a pet peeve. I always over think so I'm sure to be as correct as possible.
 

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Nothing wrong with simplicity. It's just that I've been reading so much the last six months and don't know what to believe anymore.

Of course I can try and see what happens, it's just that taking things apart again, is something I would like not to do. That's why I would try to get it as right as possible the first time. It's a pet peeve. I always over think so I'm sure to be as correct as possible.
turst me i "get" the whole paralysis thing, i'm just not sure i have ever seen anyone get it over "grounding":D

Its usually over what subwoofers to buy.:)
 

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Discussion Starter · #17 ·
I also make sure the cases (HU, DSP, amps) are grounded to the car chassis.
I've tried not to think about grounding cases and I've not seen or read about it that much. Is it a common practice to ground the cases? I guess they'll be automatically grounded if an amp rack is bolted to the chassis?
 

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turst me i "get" the whole paralysis thing, i'm just not sure i have ever seen anyone get it over "grounding":D

Its usually over what subwoofers to buy.:)
The only time I get paralysis over *grounding* is when I am laying out PCB traces for a circuit that has a combination of sensitive analog signals, high-speed digital circuits and power output devices on the same PCB. (probably only PCB designers will understand this)
 

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Discussion Starter · #19 ·
turst me i "get" the whole paralysis thing, i'm just not sure i have ever seen anyone get it over "grounding":D

Its usually over what subwoofers to buy.:)
I look at it like this: ground is something that is (or should) be pretty scientific and will (should) have an answer.

What sub to buy, doesn't have a very scientific answer and therefore I don't need that kind of certainty about that.

Made sense to me. :)
 

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I've tried not to think about grounding cases and I've not seen or read about it that much. Is it a common practice to ground the cases? I guess they'll be automatically grounded if an amp rack is bolted to the chassis?
I do not know if it is common practice.
 
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