Car Audio Amplifier, Amplifier Audio Car Install

Car Audio Amplifiers - More Good to Know Info
By George Steiner


The car audio amplifier... its soul purpose is to take a low
level signal from the source unit and transform it into a high
level signal for activating the loudspeakers.

Amplifiers range in power from about twenty watts per channel to
over one thousand watts per channel. Would you believe that the
prices range anywhere from fifty dollars to several thousand
dollars depending on features, power output and quality!
Amplifiers range from one channel of output to as many as eight
channels. The most common amplifiers are currently two and four
channel models.

Amplifier Power Ratings Power amplifiers also have "optional
equipment". These features include built-in active crossovers,
equalizers, signal processing and speaker level inputs. When
shopping for an amplifier consider that all power ratings are not
created equal. The only true measure of an amplifier's power is
its continuous power rating or R.M.S. rating ( or root mean
square) and refers to the average power output of the amplifiers.
Some of the low-quality brands will exaggerate or even outright
lie about the power output of their amplifiers which is a good
reason to stick with the well known manufacturers.

Car Amplifier Quality: Also keep in mind the quality of the
amplifier. A generally good indication of quality build and the
power output is the size and the weight of the amplifier itself.
Better quality amplifiers will usually have a heavier and larger
heatsink versus a low quality amplifier of the same power rating.

However there are many top quality amplifiers that do not follow
this rule.

Blaupunkt makes a line of amplifiers that have a plastic shell.
Because of the high efficiency design of those amplifiers a heavy
heatsink is not required. Also a good indication of an
amplifier's true output is the size of the fuse used.

Use your head when buying and keep in mind the brand's reputation
for quality.

If you find yourself on a budget or lack space for many
components then the economical thing to do is buy a multi-channel
amplifier with the built in features and processors that you
desire. By minimizing the number of components the chance of
noise entering into the system is lessened.

Some features and aspects of amplifiers to consider are:

Bridgeable: This feature allows a pair of amplifier power
channels to be combined into one channel of greater power. This
is usually used for driving a subwoofer although it will work
with any other type of speaker as well

Channels: The more channels an amplifier has the greater the
installation flexibility it will have. Especially in terms of
options, future add-ons and upgrades.

Class: This refers to the way the amplifier operates. The three
types that are most likely to be encountered are A, A/B, and D.
Class A amplifiers are the least efficient in terms of power
consumption, staying on continually, but also have better sound
in general than A/B amplifiers. They are very rare in car audio.
Class A/B amplifiers are more efficient than the class A design
and are the most common type. Almost all amplifiers in the car
audio market are of the A/B design. Class D amplifiers are
usually reserved for high power subwoofer amplifiers and can
reach efficiencies in the 80%+ range. This design can therefore
be smaller, uses less current and produces less heat than the
other classes.

Connectors: This is the method of attachment used for wires that
are connected to the amplifier, including speaker and power
wires. The most common kind is the screw terminal strip. This is
a series of screw connectors that can be removed and replaced
without compromising the amplifier. The other main type of
attachment is the "Molex" type connector. This method involves a
wire harness that plugs into the amplifier after the power and
speaker connections have been made with a crimp or solder
connection. If the amplifier is installed in more than one system
these wires can get pretty short over time and become more
difficult and even dangerous to work with. A variation on the two
is a harness that the power and speaker wires screw into. Then
the harness plugs into the amplifier. This is probably the most
convenient of all connections.

Crossover/Filter: A built in crossover can be useful, especially
if it is many frequencies of adjustment. A filter is a crossover
that only affects one channel, not actually splitting frequencies
but simply reducing a range of them.

Distortion: This is often given as T.H.D. or total harmonic
distortion. It is the measure of how much an amplifier will
change a signal from the input signal it is given. Figures below
0.1% are negligible and will not be heard. Usually the figure can
be in the 3% range without being heard but virtually all high
quality amplifiers will have a T.H.D. below 0.1%.

Efficiency: This is the ratio of of power input (from the
battery) to power output (to the speakers). A 100 watt amplifier
with an efficiency of 50% would take in 200 watts of power from
the battery and output 100 watts of power to the speakers. The
other 100 watts of power would be wasted as heat. The higher the
efficiency of an amplifier the better.

Power Output: The rated power output of an amplifier should be
given into a four ohm load, all channels driven from twenty to
twenty thousand hertz (20Hz-20kHz). Keep in mind that while the
low end amplifiers are exaggerated in their power output, many
high end amplifiers are under- rated in their power output. These
are sometimes called "cheater amps" because they allow a car
audio competitor to compete in a lower power class while in
reality having a larger amplifier. This under-rating can be three
times less than the actual power output.

Power Supply: The two most common types are the IC chip and the
MOSFET supply. The IC chip is what is used in most source units
(head units) and are only capable of roducing about twenty watts
per channel. MOSFET is the more common design and has a smoother
sound than the chip design.

Pre-amp Inputs: This is a set of jacks (usually RCA jacks) that
will accept a low level pre-amp signal from a source or
processing unit.

Pre-amp Outputs: This is a set of jacks (usually RCA jacks) that
pass on a low level pre-amp signal to another amplifier or
processing unit. These will sometimes be filtered outputs.

Separate Gain Controls: This allows the gain of each channel of
the amplifier to be set independently of the other(s).

Speaker Level Inputs: For source units that do not have pre-amp
level RCA outputs this feature may be used to take the signal
from the speaker leads of the source unit. The signal will not be
as clean as a pre-amp level output but will be adequate for most
factory upgrade applications.

Stability: The measure of how low of an impedance load an
amplifier can handle (in ohms). Any good quality amplifier will
be two ohm stable while a rare few will go as low as a quarter of
an ohm. Ideally an amplifier should double its power each time
the load is halved. For example, a one hundred watt amplifier
(into a four ohm load) should produce two hundred watts into a
two ohm load and so on. This is most useful when running multiple
speakers off of a single amplifier or in sound off competitions
that are classed by total power output.

Tri-Mode Output: This feature is available under different names
but is the ability of an amplifier to run a stereo pair of
speakers and a mono subwoofer (or center channel) from only two
channels of the amplifier. Personally, I would not recommend
doing this. Instead buy a good quality four channel amplifier and
bridge two of the channels for the subwoofer.

Tube Amplifiers: These are the least common amplifiers and are
also the most expensive. Rather than the traditional solid state
components they use old fashioned vacuum tubes. They are said to
produce a warmer sound and a moother midrange than solid state
designs. For most systems the standard design will be more
desirable.

Armed with this knowledge, you should now be able to make an
informed decision on your amplifier purchase. Interested in more
amplifier articles? Check out Putting the "BOOM...BOOM...BOOM"
into your system.

Enjoy!

George Steiner

www.1car-audio.com 
George and Judy Steiner from North Carolina have unsuccessfully
maneuvered through the teenage eons with their two daughters. The
countless boyfriends with modified auto stereo systems
broadcasting bone-jarring bass, little room to sit due to the
electronic gagets and non-existant trunks, experiences we could
have done without!
 

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