Powering another amplifier

Ti Kan ti at amb.org
Tue Sep 25 13:17:31 EDT 2001

Alexander van Gerbig writes:
>     I finally received my 2 channel ADS amplifier for the 6 1/2" speakers
> that will go into the door pockets up front.  I will have to run some
> speaker cables obviously, but I am wondering if I could feed power to this
> amp using the existing power cable to the other amp, basically put a
> junction in?  I am using 8 gauge power cable from the battery to the
> existing amp, would that be able to feed a 4 channel and 2 channel amp
> safely?

That should be fine if both amps are not ultra high powered.

It's not really a safety issue, it's just that whenever current flows
through a wire, there is going to be a small voltage drop due to the
wire's resistance.  The bigger and shorter the wire, the less resistance
and therefore there's less voltage drop.  When one amp is drawing current
via that wire, the other amp is going to "see" small voltage fluctuations
and vice versa (because the current flow is proportional to the music demand
and quickly varying) which may lead to sound quality degradations.  Such
degradation may or may not occur or audible, depending on the amplifiers'
power supply designs and the amount of such voltage changes.  There
are many variables.

Same description goes for the ground return from the amp back to the
battery '-' lead too.  It is tempting to just ground the amps to the
car's chassis, but the chassis is also the ground return for a lot of
other components of the car, many of which are electric motors, ignition
or digital devices.  Such devices add "noise" to the ground return and
that will be "seen" by the amplifier and causes noise in the audio
output.  It's best to use a big fat ground wire just as big as your
power cable directly to the battery.

These only become a safety issue if the wire gauges are too small.
At 8 gauge, this is not going to be a problem for you.  Be sure to
put an inline fuse on the battery end of your '+' wire, though, in case
of short circuits and such.

01 S4 2.7 biturbo quattro
84 5000S 2.1 turbo
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    ///  Ti Kan                Vorsprung durch Technik
   ///   AMB Research Laboratories, Sunnyvale, CA. USA
  ///    ti at amb.org
 //////  http://www.amb.org/ti/

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