Supply one or more power amplifier (with low voltage supply) for car use could require particular details to avoid important voltage drops which in turn cause distorsions on output signal or power drops in low frequency.
For low power the dimensioning of cables in a right way is enough, but when output power is higher, the absorption of peaks produces voltage drops due to the cable resistance and to the resistance of the battery itself. To maintain the same supply voltage during time you could use a capacitor which behaves such as a second battery so gives energy during the peaks and stores it when the required voltage is lower.
This app simulates the supply voltage on the power amplifiers applying to the same amplifiers a block of impulses of squared wave to the maximum power. Shape, lenght and frequency are choosen in way to cause distress to the amplifier.
Lenght of a supply cable ... L
Section of a supply cable
Contribution of the body shell (ground) ... wire M
Voltage supply at 25 °C, charged and without any loads.
Power of the battery:
Capacity of the capacitor (C):
Output RMS power (sum of the channels):
From music power : W RMS = W / 2
From peak-to-peak power : W RMS = W / 4
Characteristic efficiency of the amplifier:
Switching power supply - analogic amplifier (class B or AB).
Digital amplifier (class D).
|Peak-to-peak current required by the amplifier||A PEP|
|Average current at maximum power required by the amplifier||A|
|Total resistance considered for the supply cables||ohm|
|Internal resistance considered for the accumulator||ohm|
Options are limited only to low frequencies because the major required energy in musical tracks is concentrated on those frequencies, particularly for what concern pop music, rock music etc.
Do not exagerate with capacity of the capacitor. You will obtain best results in
terms of cost-benefits ratio where the waveshape is still visible.
When you have to deal with farad (F) the stored energy is big, so are required precautions about mounting and particular uses, you must always respect the producer indications.
You must always install a fuse before calculation on a value higher than the average adsorbed current, never on the peak-to-peak current because it can not cause the melting of the fuse.
Use a battery instead of a capacitor is fondamental wrong, it will be subject to charge-discharge cycles with high and uncontrolled current so, after a few, it will go down becoming useless.