When you have narrowed down your search by glancing at several key criteria, including the amount of output power, the size of the amplifier as well as the cost, you will still have quite a few products to choose from. Now it is time to look at some of the technical specifications in more detail. The signal-to-noise ratio is a rather essential spec and describes how much noise or hiss the amp creates. One technique to do a simple check of the noise performance of an amp is to short circuit the amplifier input and then to crank up the amplifier to its utmost. Next listen to the speaker that you have attached. The static that you hear is created by the amplifier itself. While glancing at the amp spec sheet, you want to look for an amplifier with a large signal-to-noise ratio figure which indicates that the amplifier outputs a small level of noise. One of the reasons why small stereo amplifiers make noise is the fact that they utilize elements like transistors and resistors which by nature produce noise. Typically the elements that are located at the input stage of an amplifier are going to contribute most to the overall noise. Therefore manufacturers generally are going to pick low-noise elements whilst developing the amplifier input stage. Many of recent amps are based on a digital switching architecture. The noise signal at other frequencies is eliminated through a bandpass filter during this measurement.
A weighting is a method of expressing the noise floor in a more subjective fashion. This technique was developed with the knowledge that human hearing perceives noise at different frequencies differently. An A-weighted signal-to-noise ratio weighs the noise floor according to the human hearing and is generally larger than the unweighted signal-to-noise ratio.