Today’s amps exist in all shapes and sizes. Finding the perfect type for your application may frequently be tough. There is a large number of different names and terms describing audio amps, just like “Class D” or “t amp models”. Also, each manufacturer publishes a great number of specifications, such as “SNR”, “dynamic distortion” etc. I will offer a short analysis of the output power term with the intention to help you better know the meaning of this specification and how it relates to the performance of an audio amplifier.
Several of the technical jargon which amp suppliers show regularly are misleading and do not necessarily give a decent indication of the actual functioning of the amp. Next I am going to explain the “power” rating of stereo amplifiers. This rating is one of the most basic and maybe significant specs to understand.
“Wattage” is from time to time also called “Power” or “amplifier output power”. To put it in a nutshell, “wattage” shows how high the amplifier can drive your loudspeakers. The higher this number the louder your loudspeakers. If you own a small room then you don’t require much more than several watts. If you want to install speakers outside or in a concert then you will require several hundred watts of power. Most amplifiers will have rising audio distortion as output power increases. Therefore, you want to pick an amp that offers bigger output power than you will actually need. This will assure that you will never drive the amplifier into regions of big distortion.
A number of specifications will provide the power in “Watts peak” whilst others are going to display “Watts rms”. “Peak” means that the amp is able to deliver the power for a brief amount of time only while “Watts rms” means that the audio amplifier will constantly provide that level of power. The peak spec has been rather abused by vendors stating huge peak audio power whilst their amplifiers are actually constructed with small power supplies unable to handle more than only several watts rms power.
Still, while the rms rating will tell you more about the amplifier’s true performance, be certain however that the amplifier offers a peak power specification which is quite a bit higher than the rms rating. This is because very likely you are going to be utilizing the amp to amplify music or voice. Music and voice signals inherently always fluctuate by way of their power, i.e. the power envelope of the audio is going to fluctuate over time. Having sufficient headroom is essential because music signals differ a lot from sine wave signals that are used to quantify rms output power. Brief peaks of high power are frequently found in music signals. These bursts are going to drive the amplifier into high distortion unless the peak power is big enough.
On the other hand, be conscious of the fact that the largest output power also will depend on what model of loudspeakers you are utilizing, in particular the impedance of the loudspeakers. Speakers usually have impedances between 4 and 8 Ohms. Amps have a limited output voltage swing because of the fixed internal supply voltage. As such the maximum output power is going to vary depending on the loudspeaker impedance. The smaller the loudspeaker impedance the higher the highest power the amp is able to deliver. Therefore often largest output power is given for a certain speaker impedance.