# Lots of gear going in, multiple grounds or no?



## Lanson (Jan 9, 2007)

Quick question which may warrant a not-so-quick answer. I am about to tear into my vehicle for the _n_th time, this time I hope is the last before I sell the bastard. Anyway, this is my signal chain-

Pioneer F900BT navi head unit, produces a weak 2v output via RCA. _Ground is currently bolted to the steel bulkhead tube directly behind the head unit. _ Sending 2ch RCA output full-range to...

A new item for me, the Phoenix Gold line driver. Bought this to reduce the hisssss the system currently has, which I suspect is due to the 3sixty.2. _I have no idea where to ground this item._ This line driver will send a 2ch RCA "hot" signal to...

RF 3sixty.2 processor, which sits under the passenger seat out of harm's way, takes in the 2ch RCA signal and disperses a 5ch (tweeter, woofer, and sub) signal out to my amp rack. _The processor currently derives power and ground from my amp rack location, about 6 feet worth of thick 12ga speaker cable currently serves as the power/ground run to the rack, the ground is met up to my amp rack's._

The amp rack will consist of two Rock USA amps, the big 4ch is bridged to the Ebony mids, and the little 2ch runs the tweets. _These are run 8 gauge to the amp rack ground_. The sub amp will be a TREO, which is due later today from UPS. _This will also share the amp rack ground, 4 gauge._

To slightly elaborate, this main amp ground uses the most robust thing I could find on the car, the rear seat back bracket. I ground all the paint off the bracket bottom and the paint off the unibody underneath, then sandwiched a very robust 1/0 gauge ground terminal in between. The 1/0 terminal then runs to a ground distribution block, then splits to all the equipment except the head unit.

And so, the question really is... am I causing trouble by having so many grounds? Currently I am fighting hiss and low level noise, much of which I suspect will die down when I send the 3sixty.2 a higher voltage signal w/ the line driver. Is it even remotely a good idea to ground the head unit to the amprack ground? What about the line driver, which is supposed to be connected to the system as physically close to the head unit as possible?

Thanks for the sage advice, guys.


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## Fast1one (Apr 6, 2007)

Ground loops generally occur when there is more than one path to electrical ground. Using multiple grounds for multiple audio components can indeed cause a problem, especially with picky cars. Personally I would either bring all of my grounds to a solid connection or send them to a distribution block to be sent back to B-.


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## Lanson (Jan 9, 2007)

Fast1one said:


> Ground loops generally occur when there is more than one path to electrical ground. Using multiple grounds for multiple audio components can indeed cause a problem, especially with picky cars. Personally I would either bring all of my grounds to a solid connection or send them to a distribution block to be sent back to B-.


Yeah, that's the question though. Should I ground the line driver at the head unit, or run a set of wires to the trunk? Same w/ the processor.


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## Fast1one (Apr 6, 2007)

fourthmeal said:


> Yeah, that's the question though. Should I ground the line driver at the head unit, or run a set of wires to the trunk? Same w/ the processor.


It's difficult to answer that question since every car is different. There may be no discernible difference. Personally I would run the processor and the line driver back to the amp rack with everything else. It's your call really, just wait for others to chime in


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## 89grand (Nov 23, 2006)

I've never grounded all of my equipment to one spot, and I've never had ground loop issues. Maybe I'm just lucky, I don't know.


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## Lanson (Jan 9, 2007)

Fast1one said:


> It's difficult to answer that question since every car is different. There may be no discernible difference. Personally I would run the processor and the line driver back to the amp rack with everything else. It's your call really, just wait for others to chime in


Yeah, its a tough one because I don't have ground loop noise now, just the fun noise floor of the processor. 

I will document the results of my experiment. I've got a LOT going on in the amp rack back there, I think I'm going to ground at the head unit and see if I can reduce my plethora of wires in the false floor trunk area.


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## bbaccord (Mar 7, 2007)

This is not always as clear as it may seem at first. I have my doubts that running long lengths of small gage wire just for a commin ground is a good idea. The longer the wire, the greater the DC resistance. I think having a quality ground is probably more important. 

I'm personally not a big fan of using say the ground wire alone on a radio, as the car's harness will also add length to the wire. An additional chassis ground is probably a beter idea in this case. I actually kinda liked how many of the Chryslers used that funky braided ground strap.


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## Lanson (Jan 9, 2007)

bbaccord said:


> This is not always as clear as it may seem at first. I have my doubts that running long lengths of small gage wire just for a commin ground is a good idea. The longer the wire, the greater the DC resistance. I think having a quality ground is probably more important.
> 
> I'm personally not a big fan of using say the ground wire alone on a radio, as the car's harness will also add length to the wire. An additional chassis ground is probably a beter idea in this case. I actually kinda liked how many of the Chryslers used that funky braided ground strap.


The F900BT has a fairly robust ground that goes directly from its harness at the back to, in my case, that bulkhead tube I mentioned. But yeah, I'd never use the factory radio harness ground on the car's side. That's just disaster. In my case, the factory radio's ground is a very, very large flat-woven wire running from the back to the the bulkhead tubing, raw unpainted steel. It looks more at home in the engine bay. It is a peculiar thing.


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## ryan s (Dec 19, 2006)

Well, I think I would try to keep the grounds short. For all the stuff in the rear I'd put it all in one place (that's what she said).

The 3sixty...I don't know...I'd ground it right next to where the unit will end up, same with the line driver. Or, ground the 3sixty with the headunit and the line driver with the amps.


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## DirtyDog (Jul 30, 2009)

I've got hiss myself with the f90bt which is the same unit except has 4v preouts. i removed my TLD66 as i thought it was causing the problem. it indeed was, but only because it is amplifying an existing problem. So i deal with minor hiss only when the volume control is cranked way up and i have it paused.
Very nice LD for the money. i think you will be happy.

i tried groundloop isolators with no luck. it was clearly the linedriver making the hiss louder so i made all new connections and NOT off the amps. it made the hiss get quieter which is all i wanted. granted there is no audible hiss when control knob is at 0. Only when it's cranked say at 62(max) and paused I'll get notable amount of hiss. Honestly...I think it's the HU....after all, it's not meant for SQ, but rather for dumb people...lol
i know it's not my amp(450/4) or my RCAs (MC XlnPro) or my power/ground wires (1/0) stinger pro. grounds localized on a distro and bolted to the frame 1ft away) All my RCA's are isolated away from any power sources.
Also, wouldn't you want to stick the linedriver AFTER the 3sixty.2 as it only throws out 5v signal? Or do you want the best signal going into it as possible?


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## Lanson (Jan 9, 2007)

I think I will ground at two places. The head unit bulkhead for the processor, line driver, and HU, and the amp rack ground for the amps. 

When I first put the system together, I debated over where to ground the processor for some time. I eventually decided to go to the amp rack but I think I could run a lot shorter runs to the bulkhead now that I am looking at it.


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## Lanson (Jan 9, 2007)

DirtyDog said:


> I've got hiss myself with the f90bt which is the same unit except has 4v preouts. i removed my TLD66 as i thought it was causing the problem. it indeed was, but only because it is amplifying an existing problem. So i deal with minor hiss only when the bolum control is cranked way up and i have it paused.
> Very nice LD for the money. i think you will be happy.
> 
> i tried GL isolators with no luck. it was clearly the LD making the hiss louder so i made all new connections and NOT off the amps. it made the hiss get quieter which is all i wanted. granted there is no audible hiss when control knob is at 0. Only when it's cranked say at 62(max) and paused I'll get notable amount of hiss. Honestly...I think it's the HU....after all, it's not meant for SQ, but rather for dumb people...lol
> Also, wouldn't you want to stick the linedriver AFTER the 3sixty.2 as it only throws out 5v signal? Or do you want the best signal going into it as possible?



The hiss is volume independent. I can lessen the hiss if I fool with the manual gains on the processor OR if I fool with the gains in the software via laptop. Because the RF processor can take up to 20v INPUT via RCA or speaker level, doing the line driver after the 2V head unit makes the most sense to me. I know the RF puts out a decent signal to the amps on its own, so I doubt there is a need to drive a hotter signal there.


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## IBcivic (Jan 6, 2009)

ground loops occur, when one or many devices are not well grounded and others are.
for example... the h-u and amp have good grounds but the processor doesn't.
if all ground points are solid[electrically] no looping should occur.


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## MarkZ (Dec 5, 2005)

1) Have you used the standard "noise" troubleshooting?
2) Is the noise still there when the HU's volume is at the zero setting? [could be instructive if it has zero bit mute]


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## 94VG30DE (Nov 28, 2007)

fourthmeal said:


> I think I will ground at two places. The head unit bulkhead for the processor, line driver, and HU, and the amp rack ground for the amps.
> 
> When I first put the system together, I debated over where to ground the processor for some time. I eventually decided to go to the amp rack but I think I could run a lot shorter runs to the bulkhead now that I am looking at it.


This is what I was going to suggest. Two good points of ground, and keeping the first gain section (HU to Line Driver to Processor) all at the same ground potential (using a common ground) should be sufficient. Look forward to hearing how it works out for you.


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## Thunderplains (Sep 6, 2009)

FWIW.. I ground the HU to the battery (It's power runs directly to battery as well) and EVERYTHING else is grounded to one point in rear (ground clamp to chassis bolt)

No noise. (so far)


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## Lanson (Jan 9, 2007)

Thunderplains said:


> FWIW.. I ground the HU to the battery (It's power runs directly to battery as well) and EVERYTHING else is grounded to one point in rear (ground clamp to chassis bolt)
> 
> No noise. (so far)



Yeah, no noise for me either until I insert the 3sixty.2 processor. It has always been that way, on all 3sixty.2's I've used. Just one of many reasons why I want an MS-8 so damn bad. Anyway, I think the processor noise will be significantly reduced if it is fed a much hotter signal. RF even seems to think so in their forums, and they even made a balanced line driver for things like this. Even looks like the 3sixty.2 processor.


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## kyheng (Jan 31, 2007)

I will buy a ground distribution block, all the amp's ground will go to the block. Then ground it on 1 location and lay another lenght of cable to battery's -ve directly.


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## ErinH (Feb 14, 2007)

Quck answer: If you can, then yes, go ahead and do it. At least then you won't have to tear the car apart to troubleshoot that way later. You may not have noise even if you don't, but in the world of 'one less thing to worry about', I say do it now.

I’ve got 8g power/ground for my headunit, running to the trunk to the distro block. When I went with common power/ground for everything, the result was positive. Much less system noise and no alt whine.


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## cubdenno (Nov 10, 2007)

It sounds like you mainly have it figured out with the 360 issue. I found that running a dedicated negative from my battery to the trunk stopped a slight noise issue. I chassis connected the negative at 4 places due to advice from this forum. I found that tail lights are brighter. And measured resistance is less than the chassis ground with out it.


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## Lanson (Jan 9, 2007)

bikinpunk said:


> Quck answer: If you can, then yes, go ahead and do it. At least then you won't have to tear the car apart to troubleshoot that way later. You may not have noise even if you don't, but in the world of 'one less thing to worry about', I say do it now.
> 
> I’ve got 8g power/ground for my headunit, running to the trunk to the distro block. When I went with common power/ground for everything, the result was positive. Much less system noise and no alt whine.



AHA! so you did it the "wrong" way but ended up with no noise at all. See, I was thinking about doing this exact thing with robust 8 or 10 gauge myself (for the head unit, processor, and line driver.) 

Very interesting. Did you have any noise doing it the other way before, or did you do it this way initially?


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## ErinH (Feb 14, 2007)

what's the wrong way?


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## Lanson (Jan 9, 2007)

bikinpunk said:


> what's the wrong way?



Well I used "wrong" in quotes because I don't think it is, but generally speaking most people would say it is smarter to ground with as short a ground lead as possible.


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## ErinH (Feb 14, 2007)

I didn’t take offense. I just couldn’t answer your question because I didn’t know what you meant by ‘wrong’. 


'They' say to use as short of a ground as possible due to internal resistance in wire… at least, that’s how I take it.
So, let’s use this website to calculate resistance in varying wire for X feet.
http://www.stealth316.com/2-wire-resistance.htm

At 2’, using the standard 18 gauge wire that comes with most headunits’ constant memory (yellow) you have a resistance of 0.0130 ohms, which equates to a voltage drop of 0.065V.
At 12’, using 8 gauge wire I have a resistance of 0.0077 ohms and a voltage drop of 0.0385V.

So, you can see from the above, that using the larger gauge wire allows for a lower resistance. 

Now, if you wanted to use 18 gauge wire and run it 12’, you’d have a MUCH higher resistance of 0.0783 ohms and voltage drop of 0.3915V.

And, that’s why I chose to use 8 gauge wire; less internal resistance. 

*Note: I used 5 amps for the headunit ampere rating.*


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## Lanson (Jan 9, 2007)

bikinpunk said:


> I didn’t take offense. I just couldn’t answer your question because I didn’t know what you meant by ‘wrong’.
> 
> 
> 'They' say to use as short of a ground as possible due to internal resistance in wire… at least, that’s how I take it.
> ...


You should know me by now, I rarely take offense...especially if we're in problem solving mode. 

Anywho...I'm in total agreement, I think your thought process is the right one. HOWEVER, there is the issue of a longer wire becoming more prone to induction, which always gets me thinking.


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## ErinH (Feb 14, 2007)

fourthmeal said:


> You should know me by now, I rarely take offense...especially if we're in problem solving mode.
> 
> Anywho...I'm in total agreement, I think your thought process is the right one. HOWEVER, there is the issue of a longer wire becoming more prone to induction, which always gets me thinking.


we're talking about power/ground wires. Not signal wire. AFAIK, there’s nothing for them to induct.
The only real issue you might have is the fact that you’ve simply got another run of power going through your car that might cause interference with your signal wires. But, it’s no different than your system power wire.


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## Lanson (Jan 9, 2007)

Makes perfect sense. 

Sometimes I wonder if my damn pico fuse is blown on my Pioneer F900BT. I have hot-swapped RCA's before (test and tune, did it when tweeter and woofer RCA's were backwards on the outputs of the 3sixty.2! But then again, that was on the 3sixty.2 and not on the head unit... they should be fairly well isolated I think.

Still, so many Pioneer units with blown pico's...I wonder if any of my noise is due to that. The hiss and noise doesn't increase with the pioneer's volume knob though.


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## ErinH (Feb 14, 2007)

fourthmeal said:


> Makes perfect sense.
> 
> Sometimes I wonder if my damn pico fuse is blown on my Pioneer F900BT.


Could be. Does it have one, though? 




fourthmeal said:


> Still, so many Pioneer units with blown pico's...I wonder if any of my noise is due to that. The hiss and noise doesn't increase with the pioneer's volume knob though.


Sounds like it’s something else downstream. Just guessing, but am going to say it’s your amps.
Although, have you tried to remove the line driver? Are you sure it’s not causing you any headaches?





Finally… why even worry about this? You’re about to redo everything anyway.


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## 94VG30DE (Nov 28, 2007)

bikinpunk said:


> we're talking about power/ground wires. Not signal wire. AFAIK, there’s nothing for them to induct.
> The only real issue you might have is the fact that you’ve simply got another run of power going through your car that might cause interference with your signal wires. But, it’s no different than your system power wire.


I would agree, but go a step further and say that I would think the risk of induction from your ground wire would be slim to none, given the low amount of current it is passing. You need current to induce a field, and the ground wire should not be passing much current, given my understanding of DC. Seems like the load (amp in this case) is using the current, and the ground simply gives a path to trickle off what's not used. I would love to see a amp-clamp reading on someones' scope of a power and ground wire at full load.


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## ErinH (Feb 14, 2007)

94VG30DE said:


> I would agree, but go a step further and say that I would think the risk of induction from your ground wire would be slim to none, given the low amount of current it is passing.


Which is why I didn't even bother to mention the ground wire. 


Now, if we want to be 100% certain, I'm sure someone like Chad could give his input on this. But, if I had to guess, I'd say the ground wire doesn't make a hill of beans difference regarding noise induction in relation to signal wires.


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## twosevennine (Jun 30, 2009)

why not keep all grounds where they are and just run an additional ground wire(8g or 4g) connecting everything starting at the headunit ending at your -b post?


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## 94VG30DE (Nov 28, 2007)

bikinpunk said:


> Which is why I didn't even bother to mention the ground wire.
> 
> 
> Now, if we want to be 100% certain, I'm sure someone like Chad could give his input on this. But, if I had to guess, I'd say the ground wire doesn't make a hill of beans difference regarding noise induction in relation to signal wires.


ha, you are right, I re-read your post and I see what you are getting at now. Carry on


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## sands1 (Dec 15, 2009)

fourthmeal said:


> Makes perfect sense.
> 
> Sometimes I wonder if my damn pico fuse is blown on my Pioneer F900BT.
> 
> Still, so many Pioneer units with blown pico's...I wonder if any of my noise is due to that. The hiss and noise doesn't increase with the pioneer's volume knob though.


Sounds like that could be the cause. I had what sounds like the same issue with-out the other items in your chain with the p880 and grounding the rca's took care of it.


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## Lanson (Jan 9, 2007)

I can ground my RCA's when I'm doing the line driver, no problem. Can't possibly hurt, right?


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## twosevennine (Jun 30, 2009)

twosevennine said:


> why not keep all grounds where they are and just run an additional ground wire(8g or 4g) connecting everything starting at the headunit ending at your -b post?



I guess not. lol


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## ErinH (Feb 14, 2007)

twosevennine said:


> I guess not. lol


I don't even understand what you're saying.
That would be a common ground, no?
One wire running to where he has all his grounds.


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## twosevennine (Jun 30, 2009)

Ok so he has multiple ground points right now right? why not run an additional wire connecting all the ground points together starting at the farthest away point and looping it around to the -b post? Isnt a common ground just everything grounded at one location? I'm talking multiple locations but still connected to eachother. Will that way work? or is there some sort of explanation that says im an idiot. lol


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## MarkZ (Dec 5, 2005)

94VG30DE said:


> I would agree, but go a step further and say that I would think the risk of induction from your ground wire would be slim to none, given the low amount of current it is passing. You need current to induce a field, and the ground wire should not be passing much current, given my understanding of DC. Seems like the load (amp in this case) is using the current, and the ground simply gives a path to trickle off what's not used. I would love to see a amp-clamp reading on someones' scope of a power and ground wire at full load.


The ground wire will pass the same amount of current as the power wire. Kirchoff's law. What goes in must come out as far as current is concerned.


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