The real measure of the power of an amplifier is the continuous power rating (R.M.S. rating - Root Mean Square). This refers to the average power output. Some of the lower quality brands may oversell the output of their amplifiers, so beware and best stick to well known manufacturers.

Extra features that are built into a power amplifier include equalizers, active crossovers, signal processing, and speaker level inputs. Keep in mind that doubling the amplifier power does not mean that you are doubling the sound output. This adds only 3dB of volume to the output. It takes a 10dB increase to double the sound.

A good indication of quality and the power of an amplifier are the size and the weight of the unit itself. The Class D amplifier however, is now designed more efficiently and has a smaller power supply and a smaller heatsink.

Another indication of the true output of the amplifier is the size of the fuse. A ten-amp fuse cannot be used in a 2000watt amplifier.

If you are concerned about price, you may consider buying a multi-channel amplifier with the built-in features you require. Although the quality will be a little less, this can save you space and quite a bit of money.

Common Terms pertaining to amplifiers -

Bridgeable: This allows a pair of channels to be combined into one channel with greater power, usually used for driving a subwoofer.

Channels: A channel is one power output of an amplifier. The more channels you have, the greater the flexibility for installation and the possibility for future add-ones.

Class: This is the way the amplifier operates -A, A/B, and D. Class A are the least efficient, but also have better sound. These are extremely rare for cars. Class A/B are the most common type. Class D amplifiers are usually for high power subwoofer amplifiers, reaching efficiencies in the 80% range, therefore using less current and produces less heat than the other classes. Connectors: These are the method wire connections to the amplifier, the most common being the screw terminal strip. The other is the "Molex" type connector.

Crossover/Filter: A filter is a crossover that only impacts one channel by reducing a range. Built-in filters have the option for either LP or HP. AP means "all pass" which means the filter is turned off.

Distortion: (T.H.D) This is the measure of how much change there will be in the output signal from the input signal it is given. Measures below 0.1% will probably not be heard. Anything in the 3% range will not be heard, but all high quality amplifiers have a T.H.D. below 0.1%.

Efficiency: This is the ratio of power from the battery to the speakers. A 100-watt amplifier with an efficiency of 50% would take 200 watts of power from the battery and the output would be 100 watts of power to the speakers.

Power Supply: The two most common are the IC chip and the MOSFET supply. The IC chip is used in most source units and are only produce about eighteen watts. MOSFET is more common and have a smoother sound.

Separate Gain Controls: This lets the gain of each channel to be set independently, allowing for more evenly matched channels.

Speaker Level Inputs: This feature may be used instead of a pre-amp level output to take the signal from the speaker leads of the source unit.

Stability: This is a measure in ohms of how low of impedance an amplifier can handle. A good quality amplifier will be two ohm stable.

Tri-Mode Output: This is the ability of an amplifier to run a stereo pair of speakers and also a mono from two channels.

Tube amplifiers: These are the most uncommon and most expensive. They use vacuum tubes and claim to produce a warmer sound.

The first thing you need to do is to decide just where exactly you are going to have the new amp. If there is going to be a subwoofer then it is probably a good idea to keep the amp attached to or next to the enclosure of the subwoofer. If you are simply using the main car speakers then you will want to just place the amp under the passenger's seat so that it is out of the way.

The next thing to do is to make sure that you are purchasing everything that you need to get the job done. You will need about three feet of ground cable, an RCA signal cable, a power cable, a remote on wire, and speaker wire. Make sure that you have all of the essential tools on hand as well such as wire cutters, wire strippers, screwdrivers, pliers, sandpaper, a pen, masking tape, and a 2 crimp-on o-ring ends.

Once you are ready to go you will need to disconnect the ground cable from the battery. Go ahead and connect the positive fuse cable to the positive terminal of the car battery and put the fuse in the fuse holder. Now run the power cable through your car via the firewall all the way to your amp. Look around for a metal screw or bolt on your car metal to connect the ground cable. Make sure it is close to the amp and no further away than three feet.

Now remove your head unit and run the remote and the signal on wires from the head to the amp and connect it with the RCA connectors. Make sure that everything is connected firmly to the amp and make sure that you are not left with any exposed wire hanging out anywhere. It is also important to make sure that you are securing your amp to something so that it is not bouncing around under the seat as you drive around. Put everything back to together and reconnect the cables to your battery and you should be good to go.

Checking on the ground wire of the amplifier is critical. If the wires are not connected properly, the ability for the amplifier to receive the necessary electricity is undermined. Conversely, if you are able to attach the wires properly then the amplifier should work. In general, this is the most common problem that befalls sound amplifier systems. As such, it should always be the first thing that you check.

It is also necessary to check the signal wire. Sometimes the vibrations of the car can cure this particular wire loose. Once this happens, the ability for the amplifier to receive the necessary energy source will be undermined. Conversely, connecting it will restore proper power.

Examining the reading on the volt meter is important as well. Meters are there for a reason. They tell you how much energy or juice the system is receiving. If you notice that the voltage meter is not showing a rather sizable influx of energy, then it becomes obvious that some problem exists. Whether you can fix it yourself remains to be seen. However, at least you’ll have a clear idea of where the problem is coming from.

Many times it is not the amplifier that is a problem. Remember, sound has to come through the speakers. That means a problem with the speakers will yield a problem with the sound emanating from the amplifier. As such, may be best to try a different set of speakers and see if the problem corrects itself. If so, then you no longer have to worry about any issues with the amplifier.

Thermal overload is a common problem that faces many amplifier. Thankfully, there is a gauge that tells you how hot the amplifier has become. If you notice that the thermal overload light is engaged, it may the best turn the system often let it cool. If this problem persists, the amplifier will need to be replaced or repaired as it may possess a fire hazard from overheating.

Of course, there are many other components of the car amplifier that you can check. This is just a brief rundown of some of the most common problems. It is advised if you are unable to locate the problem yourself, you can discuss the issue of qualified repair technician. After all, do not want to damage the amplifier.