Amplifiers for Home Theater
Home Audio Amps, more raw power than Iggy Pop
Amplifiers provide the muscle to your home audio system. They power your speakers by providing the electromotive force that pushes your drivers. Thinking of your amp as a powerful engine that drives your system is not far from the mark. They can be found as separate components or as part of an integrated system or receiver, a component that performs multiple tasks for your sound system including amplification. Amps built into any audio component take up the most space and can really make that surround sound receiver a heavy monster of a component. Amps as standalone components are referred to as power amps, this just means the component is responsible for nothing more than amplification and are usually the best and most expensive option for audiophiles.
A power amp will be a large rather plain looking box that may contain multiple channels or discreet separate amplifiers. The classic design of the power amp is the standard two channel model used for ages by two channel stereo systems. However, with the new digital sound formats there are several multi-channel amps available. The most common types are three and five channel amplifiers.
A three channel amp is designed as an add-on to a two channel amp to give it to all five discreet channels in a Dolby Digital 5.1 system. A five channel amp is all that's required if you have a Home Theater signal processor as a separate box. This new breed of pre-amp called signal processors are the components that decode the surround format and provide switching for the various components you connect to your system. The standalone processor requires separate amplification; a configuration that uses separate amps and processors which is aptly called separates in audio circles.
Separates have long been considered the best way to get audiophile quality from your sound system. There are many great receivers out there with built in amps and signal processors. A good separates system will just about always have it beat if you're willing to spend the money. As dedicated components, a separate amp and processor combination can do their respective jobs cleanly with less extemporaneous noise inside the box. Designers of separate components are afforded the opportunity to get more creative with the extra space. The ability to use more space under the hood to perform a single task without the constraints associated with always having to leave room for the other tasks to be performed inside the receiver is a rare task.
Whether you're buying a separate power amp or a Home Theater receiver with built in multi-channel amplification, you'll want to look for the most powerful amp with the cleanest design possible. The measure of an amplifier's power an amp is not rated in the watts-per-channel specification alone. The true power of an amp is in its ability to conduct current and dissipate heat- not something cleanly laid out in a handy specs list.
You'll have to find out more about an amp's manufacturer and seek the advice of users. Every cheap amp rates a 100 WPC spec. It seems that 100 WPC is the industry standard and manufacturer's are loath to fall short, even if they have to tweak their own specification methods to reach it. Many amplifier manufacturers routinely bloat their specifications while better quality amps routinely exceed their own manufacturer's spec.
A bold move on behalf of the manufacturer is to rate their multi-channel receiver at less than 100 WPC, often indicating that more emphasis is placed on the ability of the amp to draw current. Many mid-fi, entry level, high end amps rated at 70 and 80 WPC by manufacturer's like Cambridge Audio, Arcam, NAD, and Adcom will simply blow away 100 WPC budget offerings by the likes of Sony, JVC and Kenwood and other mainstream brands that aim for the budget minded consumer. Truly high end power amps by manufacturer's like Krell can produce high watt per channel ratings, but at the same time have very good handling of current.
Use of current in your Home Theater Amplifier
Think of current as the total quantity of energy or electricity drawn by your speakers. When the soundtrack in your movie is quiet not much energy is being used, so it's quite stable during the dialogue. Then as the tension mounts, more and more energy is drawn as the soundtrack escalates in volume; more energy is required of the amps to drive the speakers harder to push more air. Then all of a sudden one of the on-screen characters in the film narrowly avoids a blast from an RPG. An explosion rips through the hull of his Apache attack helicopter; the sound rocks the room and shakes the walls. The volume of sound suddenly spikes. This means that your amplifier better be up to the task of providing the speakers with the amount of current they need to reproduce those sounds.
Failure to handle the spike in current will result in your amplifier's clipping the sound causing distortion. Clipping output transistors is a normal reaction to their being overloaded and reaching a point called saturation. It happens all the time to cheaper Home Theater receivers and you might not even realize it; you simply lose acoustic details whenever the soundtrack gets loud. The sad thing is that if you routinely listen to music very loud, you're cheaper amp is probably clipping all the time. Take your favorite music over to a friend's house that has a higher end sound system and you may suddenly feel there are many acoustic details in your music that you had been missing at home. That's the difference between an amp that can handle current and one that cannot.
A controversial feature of an amplifier is the coloration of sound. Amps provide power to your speakers. Speakers are the mechanical device you're listening to; they provide the color, tonal qualities or timbre to your audio. Amplifiers can only color your audio with distortion, or let your speakers do what they're designed to do by staying out of the way. The best amps can do is remain neutral and not color your sound one bit. Any form of coloration to your audio by amplifiers is distortion, for better or for worse.