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Stiffening
Caps
What
are they?
What do they do, really?
This definition will be in its simplest
form. You will see audio capacitors referred to as Stiffening
Capacitors. A capacitor is a devise that stores electrical energy. Well,
you say that’s what a battery does. Well yes it does, but the
difference is the ability and speed that this electrical energy is able
to be discharged.
Batteries are designed to store
electrical energy for long periods of time. A battery also discharges
slowly. A capacitor charges and discharges very rapidly. The reason
behind this is due to the internal resistance of both devices. A battery
has a high resistance that allows for long-term energy storage and a
slow discharge. The capacitor has virtually no internal resistance,
which allows for rapid charges and discharges.
An amplifier requires current as music
signal passes through it. This creates transient signals in the
amplifier. The problem occurs when many of these signal come in rapid
succession in a short period of time. The time we are talking about are
very small fractions of a second (milliseconds). If your electrical
system is unable to react to this it causes a sagging effect in the
audio output.
As the
current goes up, so must the voltage. Since you can’t increase the
voltage as the current requirement increases we get a decrease in
voltage and this decrease in voltage causes a sagging power supply.
Amplifiers work best at 14.5 volts and can easily overcome a factory
installed alternator current output capacity.
When the engine is turned off, the system requirements are
supplied by the battery increasing the problem of supplying the
transient requirements. You could add 10 or 20 more batteries and it
wouldn’t help. Remember, as we explained above batteries can’t
supply energy quickly enough to supply the transient needs of the
amplifier. Please note that these transients may be 100 amps. They occur
so fast that your fuse will not be effected, remember this takes place
in milliseconds.
By adding a large stiffening capacitor
to your amplifier input power line you should be able to meet these
transient requirements. Remember as we explained above, a capacitor can
store energy very fast and discharge energy very fast. This should solve
the transient current requirement to the amplifier.
The voltage of the capacitor can only be
the same as the alternator output or if the engine is off, to the level
of the battery. So, as you can see a capacitor doesn’t maintain
battery levels. If you are still having energy shortages to operate your
system you may need to look into a high output alternator.
If you have any
questions, send us an email. techsupport@CarDiscountStereos.com
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