[DML] Floating ground..

[Marc Levy <malevy_nj@xxxxxxxxx>]

Part of the problem is that most people think of "-"
being the same as "ground" which is not always true. 
This is why the DMC has a sticker warning that the car
is "negative ground" or "negative earth"....  Yes,
there are some cars (mostly British) out there that
are "Positive Earth".  It is all a matter of
reference.

Audio is AC.  On the stock DMC radio, the "+" wire is
the AC output of the system with ground as the
reference.

In a high power application, they bridge the
amplifier.  Essentially, they invert the AC signal and
then amplify it.  This inverted signal becomes the "-"
with ground as the reference.

If you hook up your speaker between "+" and "-" you
will have twice the power as if you hook it between
"+" and ground.  If you hook the speaker between "-"
and ground, you will also have sound but it will be
out of phase. 

The problem is, if you hook up the "-" to ground (as
would happen if you use the VB harness), you create a
dead short.  With no load on the amplifier, you will
draw maximum current through it.  It will get hot
until it destroys itself.

Try this: (Hard to explain over e-mail!)

Draw a straight horizontal line.  This straight line
is "ground".  

Then, draw a SIN wave on top of the straight line.
0-180 deg is (at or) ABOVE the 0 line, 180-360 is (at
or) BELOW the 0 line.  This represents the "+" output
on your stereo.  The "power" is represented by the
distance from the "ground" to the SIN wave.

Next, Draw an inverted SIN wave.  This represents the
"-" output.  Now, instead of "ground" being the
reference, note the distance from "+" to "-".  It is
twice as much.

Maybe someone can dig up a web link with some
pictures.


--- Ryan Wright <ryanpwright@xxxxxxxxx> wrote:

> Hey Marc, what is the actual difference between the
> common ground &
> floating ground when it comes to wiring? Any stereo
> I've ever had (and
> I don't buy cheap, low power garbage) just connects
> black to ground.
> 



	
		
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