[Mariachi]

I just connected my head unit ground to the chassis of my car. The
music sounds a lot cleaner and my head unit amplifier doesn't turn off
when I get to relatively loud volumes. Before, I had it connected to
the factory "ground" wire and it couldn't get to very loud volumes
without switching off. Before I even connected the ground wire to the
new location, I used a voltmeter and measured voltages relative to the
positive terminal of the battery. It seems like I found a sweet spot
in the car chassis. It measured a little over 12 Volts and that was
with a dirty surface area. I cleaned off the area and ran a 14 gauge
wire with a gold plated tightened screw connection. I got sound out
of my head unit that I never knew I had before and it doesn't shut off
when it get to loud volumes either. People say that factory "ground"
wires are fine for head units, but I beg to differ. The only question
I have is if I get an amplifier, should I put the amplifier ground
wire on top of the head unit ground wire connection in order to
prevent noise? I heard many different stories on where the best
ground wire location is... what works best for you?

[MOSFET]

The only question
I have is if I get an amplifier, should I put the amplifier ground
wire on top of the head unit ground wire

I would. In fact, I do. In all my installations, I always run a 12 gauge
wire from the HU ground to the amplifier ground. This is in addition to the
HU's factory ground.

I find this helps eliminate any potential ground loops (that produce
alternator whine). Reason being both HU and amplifier will have the same
negative voltage potential.

MOSFET

[D.Kreft]

On Feb 18, 1:40 pm, "Mariachi" wrote:

The only question
I have is if I get an amplifier, should I put the amplifier ground
wire on top of the head unit ground wire connection in order to
prevent noise? I heard many different stories on where the best
ground wire location is... what works best for you?

There is no universal "best spot"...every car is different--including
those of the same make and model. All it takes is one faulty or
suboptimal weld between body parts to make for a crappy path to ground
in your vehicle. With that in mind, the rules of thumb a

0. Always secure your ground to the *chassis* of the car--not
to a bolted or welded-on piece of the vehicle.

1. Use the same gauge for the ground wire as you to do for the
power wire,

2. Keep the ground wire as short as possible,

3. Make sure that you use a wire brush and thoroughly clean
away all paint and primer from your ground location--you
should screw to nothing but shiny metal.

4. After securing the ground, it'd be a good idea to apply a
rust inhibitor over the area...WD-40, silicone spray or
white lithium grease all work well

5. Use a good-sized screw (or a machine bolt with a nut on
the other end) and always use a star washer to prevent
the non-stop vibrations in an automotive environment from
working the screw loose.

6. Try to put your ground point on the same side of the car
as the factory ground at the battery, and finally

7. Your system should have one and only one ground point.
Grounding in multiple locations is nothing but an invitation
for Trouble. As with all parties, Trouble may not come
when invited, but it's best not to go sending it an invite
unless you *do* want it rearing its ugly head.

And if you're feeling particularly adventerous:

7. Upgrade all OEM grounds under the hood:
a. battery to ground
b. battery to alternator
c. engine block to ground

Of course, if you're working on a bathtub, er...I mean a Corvette, all
of this is moot and you have only one rule to follow:

C1. Use two distribution blocks--one each for "+" and "-", and
run big, fat cables for both all the way back to the battery.

-dan

[MOSFET]

7. Your system should have one and only one ground point.
Grounding in multiple locations is nothing but an invitation
for Trouble. As with all parties, Trouble may not come
when invited, but it's best not to go sending it an invite
unless you *do* want it rearing its ugly head.


Dan, that was all very good advice.

However, IMHO, you seem to have a contradiction. You say you should keep
the grounds as short as possible AND YET you go on to say that your system
should only have one ground point. If you take the typical system with HU
and processors up front and amplifiers in the rear of the car, you are going
to have some relatively long ground wires if they are all to be grounded in
the same spot.

Soooooooooo........... It begs the question; what is more important: very
short ground wires (like less than two feet) OR grounding everything to the
same spot.

I am NOT trying to start some big argument or anything like that. I am
TRULY curious about this issue.

Thanks Dan,

Nick

[D.Kreft]

On Feb 18, 4:36 pm, "MOSFET" wrote:

However, IMHO, you seem to have a contradiction.

Yep...like all aspects of engineering, it's a series of trade-offs
(remember--you don't get something for nothing). The longer your
ground wires are, the more resistance you introduce and also the more
likely your ground wire is going to act like an antenna and pick up
radiated noise. However, more often than not, having two ground points
is the greater of the two evils.

-dan

[Captain Howdy]

Yeah Danny whats up with that? LOL..........and why should we have only
one ground point ???


In article , "MOSFET"
wrote:
7. Your system should have one and only one ground point.
Grounding in multiple locations is nothing but an invitation
for Trouble. As with all parties, Trouble may not come
when invited, but it's best not to go sending it an invite
unless you *do* want it rearing its ugly head.


Dan, that was all very good advice.

However, IMHO, you seem to have a contradiction. You say you should keep
the grounds as short as possible AND YET you go on to say that your system
should only have one ground point. If you take the typical system with HU
and processors up front and amplifiers in the rear of the car, you are going
to have some relatively long ground wires if they are all to be grounded in
the same spot.

Soooooooooo........... It begs the question; what is more important: very
short ground wires (like less than two feet) OR grounding everything to the
same spot.

I am NOT trying to start some big argument or anything like that. I am
TRULY curious about this issue.

Thanks Dan,

Nick

[Captain Howdy]

That's just krefty...........

In article .com, "D.Kreft"
wrote:


Yep...like all aspects of engineering, it's a series of trade-offs
(remember--you don't get something for nothing). The longer your
ground wires are, the more resistance you introduce and also the more
likely your ground wire is going to act like an antenna and pick up
radiated noise. However, more often than not, having two ground points
is the greater of the two evils.

-dan

[Mariachi]

On Feb 18, 9:54 pm, (Captain Howdy) wrote:
That's just krefty...........

In article .com, "D.Kreft"

wrote:

Yep...like all aspects of engineering, it's a series of trade-offs
(remember--you don't get something for nothing). The longer your
ground wires are, the more resistance you introduce and also the more
likely your ground wire is going to act like an antenna and pick up
radiated noise. However, more often than not, having two ground points
is the greater of the two evils.

-dan

say I replace the 14 gauge wire coming from my head unit with a 12
gauge ground wire. Right now, I don't even have a 14 gauge power
wire; I think it's more like 16 gauge. How would you replace the
power wire (the positive wire)? Would I just run a 12 gauge wire that
runs up to the positive terminal of the battery with a 20 amp fuse?
Or is there some resistance required between the positive terminal and
the head unit also? Right now, I have a factory positive wire
(probably a 16 gauge) with a newly added 14 gauge ground wire. You
think that's good enough for now or should I make both negative and
positive wires 12 gauge? Would it make any difference? I used 14
gauge wire for the ground because that is all I have left for now, I
used all my 12 gauge sound king wire for my 6x9's.

[D.Kreft]

On Feb 18, 8:21 pm, "Mariachi" wrote:

say I replace the 14 gauge wire coming from my head unit with a 12
gauge ground wire. Right now, I don't even have a 14 gauge power
wire; I think it's more like 16 gauge. How would you replace the
power wire (the positive wire)? Would I just run a 12 gauge wire that
runs up to the positive terminal of the battery with a 20 amp fuse?

Keeping the 6" - 12" of 18AWG that the manufacturer provides you with
coming out of the radio is fine. Remember--there's nothing magical
about bigger wires--it just means less inline resistance and less of a
voltage drop when current draw spikes.

What I used to do with more expensive systems is to run a 10 AWG power
and ground back to the system's power distribution blocks (power and
ground). The idea here is that if you have a longer run of wire, you
want to use a higher gaugue because resistance is directly
proportional to the length of the wire.

Or is there some resistance required between the positive terminal and
the head unit also? Right now, I have a factory positive wire
(probably a 16 gauge) with a newly added 14 gauge ground wire. You
think that's good enough for now or should I make both negative and
positive wires 12 gauge? Would it make any difference? I used 14
gauge wire for the ground because that is all I have left for now, I
used all my 12 gauge sound king wire for my 6x9's.

Well, whether it'll make a *noticeable* difference is up to debate and
varies from vehicle to vehicle.

Imagine you have a 4" diameter pipe that you're feeding a 10-gallon
aquarium with; and you have a standard garden hose draining it. Now
imagine that the aquarium is completely sealed and the only way for
water to get in or out is via the pipe or the hose, respectively. Do
you think that the puny garden hose is going to be able to drain water
as fast as the 4" pipe? Of course not...not without *considerable*
pressure being applied.

The same goes with electrons...you cannot put more in than you take
out nor can you put electrons in any faster than you can take 'em out.
So, if you have a 1/0 ground wire and a 22 AWG +12V wire, you might as
well have a 22 AWG ground wire. So, if you're going to use a 10 AWG
ground wire, it really only makes sense to use a 10 AWG +12V wire,
too. Note that I'm not saying it's economical or even really necessary
(given the amount of current and the distance it is being carried,
10AWG is *way* overkill)--but that's just how things work. Keep in
mind that what makes sense from an electrical engineering perspective
may not make sense from a pocketbook perspective...it's a tradeoff--
money for efficiency, and there *is* a point of diminishing
returns. :-)

And btw, you want only one ground point to minimize the possibility of
introducing a ground loop in your system. If all your ground points
don't sit at the same potential w.r.t. the postive terminal of your
battery, you'll introduce foreign currents into the system and likely
bring noise with it.

-dan
-dan

[Mariachi]

The same goes with electrons...you cannot put more in than you take
out nor can you put electrons in any faster than you can take 'em out.
So, if you have a 1/0 ground wire and a 22 AWG +12V wire, you might as
well have a 22 AWG ground wire. So, if you're going to use a 10 AWG
ground wire, it really only makes sense to use a 10 AWG +12V wire,
too. Note that I'm not saying it's economical or even really necessary
(given the amount of current and the distance it is being carried,
10AWG is *way* overkill)--but that's just how things work. Keep in
mind that what makes sense from an electrical engineering perspective
may not make sense from a pocketbook perspective...it's a tradeoff--
money for efficiency, and there *is* a point of diminishing
returns. :-)

Yeah, it makes sense that whatever line you use to input (electrons
from ground wire) must be the same size as the output (electrons going
to the positive terminal). But.... however since the total resistance
in a series circuit equals the sum of the resistances; wouldn't it be
better to have one 14 gauge wire for ground and one 16 gauge wire for
positive, than it would be to have both 16 gauges. However, it would
be more cost effective if you had both 14 gauges.

say the 14 gauge ground wire has .08 Ohm resistance and the 16 gauge
positive wire has .12 Ohm resistance... and say you just make the head
unit have a load resistance of 4 ohms.

R(total) = .08 + .12 + 4 = 4.2 Ohms

but if you have two 16 gauges

R(total) = .12 + .12 + 4 = 4.24 Ohms

two 14 gauges

R(total) = .08 + .08 + 4 = 4.16 Ohms

Therefore, the two 14 gauges is the best option, but the 14 gauge and
the 16 gauge is the next best option... get what I mean?

[D.Kreft]

On Feb 18, 9:08 pm, "Mariachi" wrote:

Therefore, the two 14 gauges is the best option, but the 14 gauge and
the 16 gauge is the next best option... get what I mean?

Yep, makes perfect sense. The message I'm trying to get across is
"don't spend all kinds of money on big, fat cables for your ground
wire if your +12V wire is skinny and pathetic," and that it doesn't
make too much sense (either economically or from and EE point of view)
to have a fat supply and a skinny return--the only thing it'll do is
make you *feel* better by giving you something to brag to your friends
about. :-)

-dan

[Captain Howdy]

For sure Einstein. E=mc2

Therefore, the two 14 gauges is the best option, but the 14 gauge and
the 16 gauge is the next best option... get what I mean?