Owner`s manual

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2
What is noise?
In any audio system, there are several potential noise sources.
• thermal noise
• induced noise
• noise caused by a ground loop
Thermal Noise
Thermal noise sounds like the hiss that you hear between stations on your FM radio. Thermal noise
occurs because mankind chooses to live at 300 degrees above absolute zero. Thermal noise occurs
because of the random movement of electrons caused by thermal agitation. At absolute zero,
thermal agitation ceases to exist. Unfortunately, we haven’t found a way around this problem yet.
Just because we live at temperatures other than absolute zero doesn’t mean that we can’t deal with
thermal noise. Careful design, along with attention to detail can minimize this type of noise.
Remember...the word is minimize not eliminate.
Induced Noise
Induced noise has a variety of causes. Induced noise is sneaky. Sometimes it gets into your system
through the power wiring, other times, it may sneak in via two adjacent wires. Still other times, it
just gets in through the air.
Although a car is powered by a battery, (and everyone knows that batteries put out pure DC) the
automobile electrical system is one of the nastiest environments known to electronic equipment.
The alternator, which generates power to recharge the battery while the engine is running, puts
high-current pulsating DC into the battery, which shows up everywhere else in the electrical
system. Alternator noise sounds like a whine whose pitch is proportional to engine speed.
The alternator wiring carries fairly high currents, even though the voltage is relatively low. Passing
an electrical current through a wire is a sure-fire way to generate a magnetic field. Higher currents
generate higher strength fields. Now, if you put two wires in close proximity to each other, and one
of them is carrying an electric current, you can generate electricity in the other by one of two
methods:
1. Move one of the wires relative to the other.
2. Vary the electric field.
Since the alternator puts out alternating current method two applies here. This is the very same
principle that a transformer (not the guys on Saturday morning TV) uses. Imagine what could
happen if the other wire was the lead from the head unit to the power amplifier.
The last cause of induced noise is electromagnetic interference (EMI). This is the same method that
radio transmitters use. Basically, the sound system’s wiring becomes an antenna, and the amplifiers
within the system become the receiver. Unfortunately you don’t want to listen to the interfering
station. Some examples of EMI are ignition noise or perhaps the loud buzz that you hear if you
drive near a television transmitter.