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Some Guidelines In Order To Help Comprehend The Noise Performance Of Latest Digital Amps

Written By Unknown on Sunday, March 23, 2014 | Sunday, March 23, 2014

By Sherry Lambert


To help you select an audio amplifier, I am going to describe the term "signal-to-noise ratio" which is regularly utilized in order to describe the performance of audio amplifiers.

After you have narrowed down your search by looking at several basic criteria, including the level of output power, the dimensions of the amp plus the price, you are going to still have quite a few models to choose from. Now it is time to take a look at a few of the technical specs in more detail. The signal-to-noise ratio is a rather important spec and describes how much noise or hiss the amp produces.

One way in order to accomplish a simple test of the noise performance of an amplifier is to short circuit the amplifier input and then to crank up the amplifier to its utmost. After that listen to the loudspeaker that you have attached. You will hear some amount of hissing and/or hum coming from the speaker. This hiss is generated by the amplifier itself. Make sure that the gain of the amps is set to the same amount. Otherwise you will not be able to objectively compare the amount of hiss between several amplifiers. The general rule is: the smaller the level of hiss that you hear the better the noise performance.

Whilst looking at the amp specification sheet, you want to look for an amp with a high signal-to-noise ratio figure which suggests that the amp outputs a small level of static. There are numerous reasons why power amplifiers is going to add some form of noise or other unwanted signal. Transistors and resistors that are part of each modern amplifier by nature create noise. Because the amplifier overall noise performance is mostly determined by the performance of components situated at the amp input, suppliers will attempt to choose low-noise elements when designing the amplifier input stage.

The most popular method for measuring the signal-to-noise ratio is to set the amplifier to a gain which permits the maximum output swing. Next a test signal is fed to the amp. The frequency of this signal is generally 1 kHz. The amplitude of this tone is 60 dB underneath the full scale signal. Next, the noise floor between 20 Hz and 20 kHz is measured and the ratio to the full-scale signal calculated. The noise signal at different frequencies is removed by a bandpass filter during this measurement.

An additional convention in order to express the signal-to-noise ratio utilizes more subjective terms. These terms are "dBA" or "A weighted". You are going to discover these terms in many amp spec sheets. This technique tries to examine in how far the amplifier noise is perceived by human hearing which is most sensitive to signals at frequencies at 1 kHz. The A-weighted signal-to-noise ratio is frequently larger than the unweighted ratio and is published in a lot of amp specification sheets.




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