Amplifiers are devices that take a teeny tiny audio signal from a pre-amp, some power from your battery, and pass it on as a big big audio signal to drive speakers.

The most important piece of advice I can give to you is to buy lots of power. To get the cleanest sound, it is absolutely essential to buy as much power as you can afford.

Here are some terms that you'll need to know when evaluating car audio amplifiers.

Watt: A watt is a measurment of power. Power is the ability to do work. In the case of amplifiers, the work is to move a speaker. Amplifiers come in all power ranges, from 20 watts per channel up to thousands per channel. When it comes to amplifiers, watts are described two ways:

RMS: An amp's power rating might say: 75W RMS x 4 CH @ 4Ω 14.4V This means that the amp is capable of 75 watts into 4 channels with 4 ohm speakers, and 14.4V of voltage. This amp is capable of providing that power if all of those conditions are met at all times. The truth is, even if you design your system to meet all of those conditions, it will not at all times. Speakers' impedences (measured in ohms, or Ω) change constantly while operating. Amps don't necessarilly put out the same power all of the time either, for example when a bass track is playing versus a much quieter track.

WHEN BUYING AN AMP, LOOK AT IT'S POWER RATING AS A MARKER FOR YOUR AMP'S CAPABILITY RATHER THAN WHAT IS LIKELY TO PUT OUT AT ALL TIMES.

However, I must also say that an amp's RMS rating is the one piece of information to look for to determine an amp's power.

CEA Compliant Power Output: This is (hopefully) going to become the industry standard for determining an amp's power output. This allows you to accurately compare two amps to each other, because you know that they were tested under the same conditions. To know why this is a good thing, click here...

MAX: Right under an amp's RMS rating, you'll see an amp's "MAX" rating. It is often double the RMS rating. The MAX rating is pure junk. Never pay attention to the max rating because it only shows what the amp is capable of in a laboratory setting. That kind of environment cannot be reproduced in the auto, and therefore the rating is misleading. An amp's max rating is proably about 50% more than the RMS. Never buy an amp based on it's Max rating. Ok, and lastly, because this makes you look like a total jerk, never ever ever say your amp is a 1000 watt amp because it has a max 1000 watt sticker on it, and ESPECIALLY if you bought your amp at the swap meet. 1000 watt amps are BIG and HEAVY.

Anyway, in summation, never buy an amp based on it's MAX rating.

CEA Compliant Power: (CEA=Consumer Electronics Association) This spec (if your amplifier includes it) is a new rating. The goals of this rating are to give a useful reference for amp comparison. In the "bad old days", amp manufacturers could pretty much claim whatever power output they wanted without specifying the testing methods. The CEA rating changes that. The CEA compliant power output specifies what power output you can expect when the following criteria are met: 14.4V, 4 Ohm speaker load and 1% distortion. You can now fairly compare two amplifiers to each other because you know they were tested in the same manner. Make sense? No? OK, look at it this way: If an amp has a CEA compliant output power of 100 watts per channel, you know that the amp is essentially equal to another amp with the same CEA rating. HOWEVER, you cannot compare this amp to another amp that is rated at 100 watts/channel RMS.

I am a big fan of this rating. FINALLY, there is a uniform standard for amplifier power output ratings. If an amp doesn't include this spec, then the manufacturer is probably trying to hide something.

Bridging: Many stereo and 4 channel amps allow you to "bridge". What you do with bridging is combine two channels into one, or four channels into two. This allows you to allocate more power to a single speaker, like a subwoofer for example. This is a handy feature for someone who has a stereo amp lying around, but they want to use all of its power to drive a single speaker. There's nothing wrong with bridging, and is often used for subwoofers.

Crossover: Many amps have a simple crossover built in. Basically, it will be a switch that will have three positions: high pass, low pass, off. High pass basically allows all of the higher frequencies to pass. This is handy if the amp is powering tweeters and mids. The low pass allows only the lower frequencies to be reproduced. This is handy if the amp is powering a subwoofer. Off means that all frequencies will be sent to the speaker.

Bass Boost: Some amps have a circuit that when switched on gives a boost to your bass. It is not essential, and I usually don't use it in my own system.

Frequency Response: This specification tells you what frequencies that the amp responds to. Higher frequencies are treble, lower frequencies are bass. The human ear can perceive from 20hz to 20,000hz (aka 20khz). Most amps will reproduce this frequency band with ease. Some will go above and beyond. Don't worry about that because usually CDs don't contain data out of that range, and even if they did, you wouldn't hear it! Some people talk about harmonics, and I don't know if it's true or not. But whateva. Read about this debate elsewhere.

Channel: Amps have channels that basically tell you how many loads it is built to drive. Loads=speakers, so a two channel amp will power two speakers.

Classes:

Different amps have different designs that all achieve the same thing (amplifying a musical signal), but achieve this in different ways. The way in which the amplifier is designed is refered to as its "class". There are 4 major types of classes, and an occasional oddball. I don't really know the technical differences between them, but it doesn't matter. We're just installing amps, not designing them!

A - Very good sound quality, very inefficient, uses boatloads of power, and wastes most of it in the form of heat.

B - Good sound quality, moderately efficient, uses a lot of power, wastes about half of it in the form of heat. Some "crossover distortion" present

A/B - Combination of classes A and B. At low volumes, uses the class A portion of the amp. At higher volumes, uses the class B portion of the amp.

D - So-so sound quality (but reproduces bass very well), highly efficient, uses minimal power, wastes very little of it.

Other classes: Whatever. They exist. I don't know if they sound better. Your ears are the best judge.

THD: This stands for "total harmonic distortion", but the D is all you have to pay attention to. Obviously, the lower this number, the better. You don't want your amps producing distortion and sending it to your speakers! It causes noise and speaker damage. The experts say any THD rating below 0.1% is inaudible, meaning you can't perceive it. But remember that distortion travels through all components, and is amplified by each one. So, having a low distortion amp, and other high distortion items in your system will reproduce distortion.

S/N Ratio: A Measure of how an amplifier silences backround noise. This spec is measured in db, and the HIGHER the s/n ratio, the cleaner your sound.

Speaker Level Inputs: This feature allows you to connect the amp to your system through speaker wires (instead of RCA cables). This feature is handy if you're adding an amp to your factory stereo system.

Preamp Outputs: This feature allows you to connect an RCA cable to the amp to supply a second amp with the musical signal. This feature is handy if you want to add a second amp without running a cable all the way from your head unit to the amp. Also, it allows you to add an additional amp to a head unit that may have only one set of RCA pre-outs.

Remote bass control: This feature allows you to control the bass output of the amp without having to adjust it on the amp. You can mount the control wherever's clever, and adjust the bass remotely.

HOW TO DETERMINE WHICH AMP IS BEST FOR YOUR SYSTEM:

How many channels is your system?
How to hook up those channels.
Features you want

Crossover:
Inputs:

speaker (hi level)

rca, pre-amp (lo level)

How many channels are you going to drive? We already discussed the ranges of stereo systems, so you need to determine how many speakers you're driving. Say you want to build an intermediate system with 6 speakers. You figure you want to amplify all 6 of those with a "real" amp. You can go a few routes: You can buy a 6 channel amp, or a 5 channel amp, and power your whole system. That makes life easy if you want to keep installation clean and simple. You could also power your speakers with multiple amps: One mono, one 4-channel, you could even use three stereo amps. If you want to get really fancy, you could bi-amp your component speakers, bringing your amp count to 3, 4, and 5 amps!

One way that you can get creative with your installation is through bridging. If you want to power 2 or more subs on a stereo amp, you can bridge it, or combine the two channels into one. From there, you can wire your subs in parallel or series to obtain the proper ohm load. It's an easy way to power multiple speakers on one amp.

To save money, you can always opt not to install an amp for the rear speakers. I often times just power them off of the head unit. If I am listening to music without rear passengers, I can just fade the head unit to the front, leaving me with the amplified front speakers.

Do you need an amp to have a crossover?

Crossovers come in handy when you are powering subwooers. Most amps can reproduce the entire range of human hearing. However, when we install subs, we only want them to reproduce bass. If the amp has a crossover, you can turn it on, and essentially tell the amp to only send bass to the subwoofers. Since subs can only reproduce bass, why have the amp waste energy sending the subwoofers frequecies it can't reproduce? LUNACY I TELL YA!

Inputs

speaker: These are called high-level inputs because the signal is already highly amplified. Get an amp with high-level inputs if you are integrating an amp with a factory head unit.

rca: These are called low-level inputs because the signal is not highly amplified. These inputs are RCA style, and are preferred because they produce lower noise. This is the best option if you are using an aftermarket head unit.

You have with you DVDs from different parts of the world, including that British TV series DVD that you wanted to get for a long time. You are now back home and waiting for the opportunity to play that DVD. What could be a better time than this when you are off to a holiday with your car? You want your family to watch that DVD while you drive. When you try to play the DVD, you are surprised to see the words "wrong region" coming up on the screen. You do not understand what that is. Is your car DVD player not working? Or is it that the DVD is faulty? The packing in which the DVD came says that the DVD is region free, which would mean that the DVD is meant for Region 0, that it is region free. What could be the problem? You are not being able to figure this out.

A region 0 or a region free DVD plays on all DVD players, if the player is region free. But there remains the question of mismatching of the video formats. It is the question of compatibility between Phase Alternating Line (PAL) and National Television System Committee (NTSC). Your portable car DVD player, which you bought from the United States plays only NTSC standard DVD, while the DVD that you had bought from the United Kingdom has a PAL video standard. Even if the DVD is based on digital format, it matters less when the DVD has a PAL standard and you are trying to play it on your portable car DVD which is in NTSC. That DVD will not play in your portable card DVD player.

The so called regions, that we hear so much about when buying a DVD disc or a player, are catagorised in the following way:

1. Region 1 - The U.S., U.S. territories and Canada

2. Region 2 - Europe, Japan, the Middle East, Egypt, South Africa, Greenland

3. Region 3 - Taiwan, Korea, the Philippines, Indonesia, Hong Kong

4. Region 4 - Mexico, South America, Central America, Australia, New Zealand, Pacific Islands, Caribbean

5. Region 5 - Russia (okay, former Russia), Eastern Europe, India, most of Africa, North Korea, Mongolia

6. Region 6 – China

7. Region 0 – All the countries in the world.

There are mainly three basic television broadcast standards in the world and these are, Phase Alternating Line (PAL), National Television System Committee (NTSC) and Séquentiel couleur à mémoire, French for "sequential color with memory" (SECAM). These three standards are incompatible wit each other, which would mean that all both, the DVD and your portable car DVD player have to be of the same standard.

NTSC standard was developed in the United States and the first ever colour broadcast came to that country in 1953. This was obviously based on NTSC standard and is now being used by many other countries in the American Continent as well as Japan and the Philippines. It has 525 horizontal scan lines at 60Hz frequency, for which it is sometimes referred to as "NTSC-525". Out of the 525 lines, 486 lines are visible on the screen and the rest are synchronisation pulses, and for one, these are used to reposition the electronic gun in a television. Each of these visible lines is made up of 720 pixels, giving a total screen resolution of 720x486. NTSC has a frame rate of 29.97 frames per second which is rounded up and referred to as 30 frames per second.

PAL was developed in Europe and was introduced in early 1960's. PAL was available in most of the European countries by that time, except France, who developed their own SECAM system. PAL works on 625 lines per frame at 50Hz frequency. PAL uses a wider channel bandwidth than NTSC which provides a better picture quality. PAL has eight versions and these are PAL B, PAL G, PAL H, PAL D, PAL I, PAL K, PAL K, PAL N and PAL M. All of these have different specifications from each other. PAL is used in China, India, Indonesia, Israel, Laos, Nepal, Pakistan, Thailand, Lebanon, Iraq, Iran, and United Kingdom, some European countries, some countries in South America and also in Africa.

SECAM uses frequency modulation technology to encode chrominance information on the sub-carrier. Chrominance along with luminance is one of the two components of a television signal. It defines the two attributes of a colour. The hue of the composite picture is defined by the frequency, while the saturation defines the amount of black. Luminance is the mathematical component of the red, blue and green components in a colour television. This combination is used to produce other colours on the television screen. SECAM has the same bandwidth as PAL and operates on 625 lines per frame.

Region free portable car DVD players are capable of playing all region DVDs regardless of the region code of the discs. These DVD players have built-in code converters, which lets any region DVD to be played on such players and viewed on the screen. These portable car DVD players play any zone, area, region code DVD without any additional equipment. You can play any region, any code, PAL or NTSC DVDs from Europe, Asia or anywhere in the world. Region free portable car DVD players are those which do not have an internal region lock and hence they are universal players, and they can play DVDs from any region as shown above. These are specifically called Region 0 DVD players, which accept code locked DVDs from other regions.

One does wonder why the region wise coding is done in DVDs. Some say it is the only way by which one could project the right of issue of such DVDs. The other aspect, which is being conjectured, is to maintain the price of the DVDs at the regional level. For example, a DVD movie, which has been released in the United States, is priced quite high compare to the price as and when it is available in India. Therefore, with regional codes built in the DVDs, it will be difficult to play the same DVD in the United States, which has been coded for India.

In many legal views code enforcement is a violation under the WTO free trade agreement. The coding of the players violates this specific law. This coding of DVD players has been seen as a serious violation of Trade Practices Act, as per the law set down by the Australian Competition and Consumer Commission. A similar ruling also exists in New Zealand. As a result the DVD players, which include portable car DVD players, sold in Australia and New Zealand, are all of region 0 standard, meaning that the players are capable of playing any DVD, irrespective of their region coding.

Loving your Car Audio System is not based on how big or impressive it looks, but on how satisfied you are with your purchase. Some few years back, once your car audio system could play a cassette and sound off with a radio, you were satisfied. Nowadays, a simple car audio is one that has both MP3 and CD players.

New Car Audio Systems can co-exist with the old as long as the installation is handled professionally. Of course, in this case it would be better to buy a car audio that is specially equipped for this precise use. The lights on automobile sound systems of this age are guaranteed to keep you happy with your purchase, just from the way they look. The relevance of all the above is actually in question, save for the LCD display that shows what track is playing. To suit the varying tastes of car users, equalizers adjust outputs, middle and treble levels. While some car audio systems stick to CDs, others can play in the CD or MP3 format. Owners who plan to use MP3s cannot disregard the use of a CD system.

You can buy either one, or both types, depending on the function you want. Since tweeters are meant for minimum noise they should be in front, but the bigger noisier elements should go in the back, and this is especially wise for a basic car audio system. It goes without saying that buying speakers like this from the start will save unprecedented cost on the long run.

Stores, where vehicle parts are sold, sell automobile sound systems, as do other stores. Because of the chances of buying a spectacular looking Car Audio System that does not go down well with you, discuss at length with your dealer before purchase. All you need to know like the specifications, functions, and performance statistics; even pictures of Car Audio Systems, are on websites where you can easily have access to view them before purchase.

So, you just finished watching MTV's "Pimp Your Ride" and you need to add a little something different to make your car stand out from the crowd. What can you do? How about adding Mobile Internet to your vehicle. It is not as hard or expensive as you might think.

Here is what is needed:

Mobile Router:

This is similar to a typical home router with one exception. It uses a Sprint Mobile Broadband Card to provide the internet, allowing you to use it anywhere, even in motion! It converts a Mobile Broadband Card into a Wi-Fi signal that up to 5 laptops can use at the same time. One of the best options for this would be the Kyocera KR1 Mobile Router. Why? It is the least expensive mobile router on the market at well under $200. Secondly, unlike most other mobile routers it comes standard with a Car Charger. Just plug it into the cigarette lighter and the unit is now powered up and ready to surf the internet, even while driving down the road at 75 MPH. Of course, that would be for the passengers to enjoy, not the driver!

Mobile Broadband Service:

This is the increasingly popular Mobile Internet service that Sprint, Verizon and others are now selling. For just $59.99 a month, Sprint offers unlimited internet access anywhere in the USA. For the same price, Verizon offers up to 5GB a month. These services can be used directly in a laptop for one user, or in this case, directly into the Mobile Router so that multiple users can tap into the same card at the same time.

Laptop:

This one is quite obvious, but there are two ways to connect the laptop to the Mobile Router. One is with an Ethernet cable, as the KR1 has 4 Ethernet ports in the back. The second and easier way would be to just connect through wi-fi. As long as the laptop has built-in wireless, as all newer laptops do, the laptop will find the wi-fi signal the Mobile Router is producing.

Extras:

If extra range is needed on your Mobile Internet set-up, or if the vehicle is often in remote areas there are two products that can greatly increase your performance. The first is an external Antenna. All the current Mobile Broadband Cards have ports to attach these antennas, enabling a more powerful antenna to boost the signal and thus the performance of the card. Amplifiers are even more beneficial. These devices add up to 3 watts of power to the Antenna, which can turn a very weak signal into an average or even strong signal. Not only will these add-ons help your performance, but they will add a bit of the "WOW" factor when people are admiring your unique vehicle.