There is so much that can be said about power amplifiers that entire books have been written about them.
According to attributes, power amplifiers are classified alphabetically, usually A through D, or more specifically Class A through Class D.
Without being cognizant of it, we encounter amplifiers in every area of our lives. For example, there are power amplifiers in hearing aids and laptop computers, the mp3 player and/or radio in your car, guitar amps, keyboard amps - they all operate on the same basic principles.
Let's discuss the basics of power amplifiers for live sound reinforcement for worship, which are the very same used in secular concert sound systems. My hope is that, after reading this article, you will be able to make an informed decision when considering a power amplifier purchase for your house of worship.
Converting low-level audio into audio strong enough to move loudspeaker cones or drivers, power amplifiers have been a necessary component in the signal chain for almost as long as audio systems have been in existence.
Power amplifiers are an electronic component that convert a small electric current into a larger one. That electric current is commonly referred to as the signal. The measurement of that output signal is called the gain or gain factor, and most often referenced in decibels (specifically 10 times the logarithm of the output power divided by the input power).
Power amplifiers are designed to inherently work better at some frequencies than others, and no power amplifier is perfect for every application. While choosing a power amplifier for your application, there's usually a trade off on one particular attribute or another. Some power amplifiers are better at delivering gain (or boost of signal), while some are better at linearity (how closely the output matched the input, often also referred to as "fidelity"), or efficiency (how much power is wasted in the amplification process).
According to attributes, power amplifiers are classified alphabetically, usually A through D, or more specifically Class A through Class D, indicating whether an amplifier is optimized for efficiency, linearity or a compromise between the two. Class A power amplifiers provide the best output quality (the best linearity), but tend to be inefficient, heavy, large, run hot, and are power hungry. Class B power amplifiers offer less linearity, but are less expensive, operate at a lower temperature, and are more efficient. Class AB, as you might imagine, offer an output quality of a Class A and the efficiency of a Class B.
Class C have higher efficiency, but the output quality is poor. Class A power amplifiers tend to deliver a more musical sound, while Class C amplifiers are better suited for speech only such as a warehouse public address system. With Class D technology, those type of amplifiers are becoming increasingly utilized, since they offer more power, with notably less weight, particularly those that are Class A.
Some of the most respected loudspeaker manufacturers have become very active in proprietary power amplifier designs. The power amplifiers designed by these brands are made to be used exclusively with specific models of their brand of loud speakers and are fully programmable. In addition, there are some loudspeaker manufacturers that have power amplifiers built into their loudspeaker enclosure. This is a very convenient design, although it does make for a very heavy loudspeaker (or floor monitor). It's extremely beneficial to have the amplifier so easily accessible for maintenance and troubleshooting, as opposed to an amp room that is set up in a remote location.
As always, I intentionally avoid mentioning any particular manufacturer, so as not to appear to endorse one amplifier manufacturer over another.
Again, I hope I've offered enough information so that an informed decision can be reached when you're in the market for an amplifier to match your loudspeakers.
Please keep in mind that there are many more aspects to consider that were not covered in this article, such as the mode in which the power amplifier will be used (bridged, to perhaps power sub woofer speakers, or not), wattage, ohms, impedance, types of connectors, etc.
The most important consideration to remember is that the power amplifier must match your loudspeaker, in that the power handling limits of the loudspeaker are not exceeded, or you will risk damaging the loudspeaker.