Amplifiers supply home theatre speakers with clean power for high-quality sound. The most important features and specifications to look for when shopping for home audio amplifiers include the continuous power rating, the number of channels, the distortion rating, the signal-to-noise ratio, and the dynamic headroom. Understanding them is the key to finding an audio amplifier that helps create an immersive home theatre experience.
Continuous Power Rating
The total power output of an amplifier is one of the main factors that determine the volume of the speakers. Depending on the number of channels the amplifier can put out, the power rating may be in watts-per-channel, or WPC. This should generally be somewhere between 50 and 100. Some manufacturers give the maximum power rating rather than the continuous power rating. This is misleading because the amplifier can only sustain the maximum wattage in brief spurts. Look for a total power or WPC rating in "RMS" terms, which means it refers to the continuous power specification and consider the rating in the context of the distortion and other specifications.
Number of Channels
The number of channels determines the number of speakers that can connect to the amplifier. Obviously, this needs to match the set-up of the home cinema system. When buying speakers along with the amplifier, you have many more choices in the amplifiers that may suit a certain space. Especially for small rooms, a full Dolby 9.1 set-up is not necessary if a smaller system with a subwoofer, two midrange speakers, and two tweeters can do the job.
A high power output does not mean high-quality audio unless the audio amplifier also offers low distortion. The Total Harmonic Distortion (THD) should be as low as possible, ideally at or below 0.5 per cent. Anything above 1 per cent THD is likely to sound very distorted at high volume, thereby defeating the purpose of buying an amp with high wattage.
The signal-to-noise ratio describes how clear the main voices or instruments are in comparison to the background noises. This is more important for movies than music because a low signal-to-noise ratio means it might be hard to hear the characters speaking when there is a lot of background noise. The ratio commonly ranges from 50 to 100 dB, and higher values are more desirable.
Dynamic headroom refers to how much extra power an amplifier can put out in brief spurts when necessary. Related to the maximum power output, the dynamic headroom is important for music or movies that have big changes in volume suddenly. When the continuous RMS power is insufficient, the dynamic headroom determines how well the amplifier holds up. A 3 dB dynamic headroom means the amp can double its output for a brief period.