Amplifiers-What to look for

RMS Power vs Peak Power

The RMS rating tells you the amount of power (watts) an amplifier can produce on a continuous basis. The peak rating tells you the maximum wattage an amp can deliver as a brief burst during a musical peak. The RMS rating is more significant.

Regulated Power Supply

Regulated power supplies help to maintain the output of an amp under verying conditions. Pulse Width Modulation is the tightest form of power regulation among the higher end audio manufacturers. It maintaints a rock-steady output regardless of voltage lapses caused by other electrical demands placed on your car`s battery.

Some competition style amps opt for very little power regulation so they can pass unusually high current at very low impedances (down to 1/2 an ohm in some cases).

Amps without a regulated power supply are called "bridged transformerless"(BTL) amps. They are limited to about 20 watts RMS  per channel and the channels can not be bridged together.

Bridged Power

In mono mode , you "BRIDGE" (combine) the stereo output to power a single speaker. Bridging 2 channels into 1 is perfect for driving single or multiple subwoofers.

Discrete Output Devices

Amps with discrete output devices use seperate transistors instead of integrated circuits on each output. They can pass more current and consequently play louder and cleaner. They are a must for driving subwoofers.

2-Ohm Stable

These amps are "STABLE" and run cool when driving a 2 ohm load. These amps allow you to wire 2 4 ohm speakers in parallel without stressing the amp.

In most amps, as soon as 2 channels of an amp are bridged, the bridged mono channel is not 2 ohm stable. In other words, you CAN NOT wire speakers in parallel off a bridged amp.

Tri-Way Output vs 3-Channel Output

Tri-Way mode powers a pair of stereo speakers and a subwoofer simultaneously with a single 2-channel amp. It is an affordable way to drive a subwoofer and requires an external Tri-Way crossover that is connected in line between your amplifier and your speakers.

In3-channel mode, you bridge the rear channels of a 4-channel amp to drive a subwoofer, while the front channels drive a pair of full range speakers.

Mosfet

MOSFET (Metal Oxide Semiconductor File Effect transistors) have a higher switching speed than bipolar transistors and generate very little heat. They offer fast response and are highly efficient.

THD or Total Harmonic Distortion

Amount of change in harmonic content of the signal as it is amplified. A lower figure indicates a more accurate amp. THD below 0.10% is inaudible.

Built in Features to help you get bass as big as you want

A powerful amp can be a powerful ally in your quest for BIG BASS. But don`t overlook equally helpful built-in features that will save you some cash and installation time and problems.

Choosing an amp that has a built in low pass filter means you don`t need to buy and install a seperate crossover to make sure your circuit will boost low-level frequency information, so you will feel those low frequencies even more.

Options for Multi Amp Systems

Many amps include output jacks with built in high and/or low pass crossovers that let you "daisy chain" several amps together. Choosing an amp with these features built-in, means you can run a multi-amp system without spending money on a seperate electronic crossover.

If the amp you like doesn`t have output jacks or built-in crossovers, you can still run multiple amps. Electronic crossovers offer complete system control by letting you vary crossover points and adjust relative volume levels of different amps. You can tweak your system to perfection.

Where and how to Mount an Amp

Most installers like to mount amps so they aren`t visible from the outside of the vehicle, but you will have to decide what is best for your application. Amps mounted under seats require shorter power and RCA cables & are generally closer to the rear deck speakers or subwoofer boxes