Subj: RE: re: prince of deafness: cassette player static
>> a cheapo stereo and the noise was really bad, I put a 150,000 uF
>> capacitor across it, one of those beasts found in a computer power
>> supply. It is the size of a tall boy beer can. I strapped it on the
>That's a very bad solution, if you don't have a coil between the
>battery and it. The cap is likely to interact with the battery
>and alternator/generator in such a fashion as to melt the wiring.
>No need to smooth out the voltage in the whole electrical system,
>just at the input to the stereo.
Actually, no it won't damage the wiring. A cap only draws current when it's
charging up (which is a very short time period). Large caps are used in power
supplies to filter out low frequency noise, which is one of the things you want
to do in an auto, since an alternator produces AC which is then rectified to
produce DC. Most GOOD noise suppression kits have a combination cap from + to
ground and an in-line choke. To DC, a cap looks like an open and a choke
appears as a short. Don't forget, no matter where the cap is placed along the
power line, you're essentially putting it across the whole 12v system to
ground. The bigger the cap the better (number of uF's) the filtering, if you
do use a large one, just make sure the terminals are covered and a bleed off
resistor is installed across the +/- cap terminals (~15K, 1 watt will do), to
prevent accidental discharge, which can burn you. A couple of other items to
cut stereo noise are:
-A good ground strap from the engine/tranny to the body.
-Resistor plugs.
-If the stereo uses chassis ground for the - side of the speakers, run both +/-
from the speakers and attach the - directly to the chassis of the stereo; don't
ground the speakers on the body somewhere away from the stereo.
-A good noise suppression kit.
-Since my stereo and amp draw about 10 amps total, I connect the hot directly
to the battery.
Mike G.
gendimen@t12sys.intel.com
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