Re: stock radio in front, mp3 player and amp in back

One more note on this.  Depending on your AMP, you may need to apply
voltage to this wire or ground it. For voltage,  I usually use an
existing circuit in the car that is hot in accessory.  In this case no
need for resistor.  Current is not an issue, but you do want to have
the AMP off when the ignition is off to prevent slowly draining your
battery.  If your AMP requires a ground on this wire (check the manual
to be sure), then you should use a diode or resistor to limit the
voltage drop across the amp sense circuit.  In this case I usually use
a transistor or relay to ground the AMP sense circuit when the key is
on (agaon, accessory or run) and open the circuit when the key is off.
 Let me know if you need more details about this circuit, I can gin up
some pictures.

John

> It just has to sense
> something, so hook up a resistor and a switch. 
-- 
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= Never offend people with style when you   =
= can offend with substance --- Sam Brown  =
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