It is easy to be baffled by the terminology which amp manufacturers use to depict the performance of their models. I am going to clarify the meaning of a regularly used amplifier specification: "signal-to-noise ratio" to help you make an informed decision while purchasing a brand new amplifier. As soon as you have chosen a number of amps, it's time to investigate a few of the specs in more detail to help you narrow down your search to one product. One important parameter of power amplifiers is the signal-to-noise ratio. To put it simply, the signal-to-noise ratio shows how much hum or hiss the amp will add to the music signal. This ratio is generally described in decibel or "db" for short.
You can perform a simple assessment of the amp hiss by short circuiting the amp input, setting the gain to maximum and listening to a loudspeaker attached to the amplifier. Generally you will hear two components. The first is hissing. In addition, you will frequently hear a hum at 50 or 60 Hz. Both of these are components which are created by the amp itself. Next compare different amplifiers according to the next rule: the lower the amount of hiss, the higher the noise performance of the amplifier. Yet, bear in mind that you have to set all amps to amplify by the same amount to evaluate different amplifiers.
A method in order to do a straightforward check of the noise performance of an amplifier is to short circuit the amp input and then to crank up the amplifier to its utmost. After that listen to the speaker that you have connected. Usually you are going to hear two components. The first is hissing. In addition, you will frequently hear a hum at 50 or 60 Hz. Both of these are components which are created by the amp itself. Next compare different amps according to the following rule: the smaller the amount of noise, the better the noise performance of the amp. However, keep in mind that you must set all amps to amplify by the same level in order to compare several amps. Whilst looking at the amp specification sheet, you want to look for an amplifier with a large signal-to-noise ratio figure which indicates that the amp outputs a small level of noise. There are numerous reasons why power amplifiers will add some form of noise or other unwanted signal. Transistors and resistors that are part of each modern amplifier by nature make noise. Mostly the components that are located at the input stage of an amp will contribute most to the overall noise. Thus producers typically will pick low-noise elements when developing the amplifier input stage.
Many today's power amps include a power switching stage that switches at a frequency around 500 kHz. This switching noise can cause a certain amount of speaker distortion yet is typically not included in the the signal-to-noise ratio which only considers noise between 20 Hz and 20 kHz.
The most common method for measuring the signal-to-noise ratio is to set the amp to a gain that allows the maximum output swing. Subsequently a test tone is fed to the amplifier. The frequency of this signal is usually 1 kHz. The amplitude of this tone is 60 dB below the full scale signal. Subsequently, only the noise between 20 Hz and 20 kHz is considered. The noise at different frequencies is removed by a filter. After that the amount of the noise energy in relation to the full-scale output wattage is calculated and expressed in decibel.
Frequently the signal-to-noise ratio is expressed in a more subjective way as "dbA" or "A weighted". This technique was designed with the knowledge that human hearing perceives noise at different frequencies differently. Human hearing is most responsive to signals around 1 kHz. On the other hand, signals under 50 Hz and above 13 kHz are barely heard. An A-weighted signal-to-noise ratio weighs the noise floor in accordance to the human hearing and is typically higher than the unweighted signal-to-noise ratio.
You can perform a simple assessment of the amp hiss by short circuiting the amp input, setting the gain to maximum and listening to a loudspeaker attached to the amplifier. Generally you will hear two components. The first is hissing. In addition, you will frequently hear a hum at 50 or 60 Hz. Both of these are components which are created by the amp itself. Next compare different amplifiers according to the next rule: the lower the amount of hiss, the higher the noise performance of the amplifier. Yet, bear in mind that you have to set all amps to amplify by the same amount to evaluate different amplifiers.
A method in order to do a straightforward check of the noise performance of an amplifier is to short circuit the amp input and then to crank up the amplifier to its utmost. After that listen to the speaker that you have connected. Usually you are going to hear two components. The first is hissing. In addition, you will frequently hear a hum at 50 or 60 Hz. Both of these are components which are created by the amp itself. Next compare different amps according to the following rule: the smaller the amount of noise, the better the noise performance of the amp. However, keep in mind that you must set all amps to amplify by the same level in order to compare several amps. Whilst looking at the amp specification sheet, you want to look for an amplifier with a large signal-to-noise ratio figure which indicates that the amp outputs a small level of noise. There are numerous reasons why power amplifiers will add some form of noise or other unwanted signal. Transistors and resistors that are part of each modern amplifier by nature make noise. Mostly the components that are located at the input stage of an amp will contribute most to the overall noise. Thus producers typically will pick low-noise elements when developing the amplifier input stage.
Many today's power amps include a power switching stage that switches at a frequency around 500 kHz. This switching noise can cause a certain amount of speaker distortion yet is typically not included in the the signal-to-noise ratio which only considers noise between 20 Hz and 20 kHz.
The most common method for measuring the signal-to-noise ratio is to set the amp to a gain that allows the maximum output swing. Subsequently a test tone is fed to the amplifier. The frequency of this signal is usually 1 kHz. The amplitude of this tone is 60 dB below the full scale signal. Subsequently, only the noise between 20 Hz and 20 kHz is considered. The noise at different frequencies is removed by a filter. After that the amount of the noise energy in relation to the full-scale output wattage is calculated and expressed in decibel.
Frequently the signal-to-noise ratio is expressed in a more subjective way as "dbA" or "A weighted". This technique was designed with the knowledge that human hearing perceives noise at different frequencies differently. Human hearing is most responsive to signals around 1 kHz. On the other hand, signals under 50 Hz and above 13 kHz are barely heard. An A-weighted signal-to-noise ratio weighs the noise floor in accordance to the human hearing and is typically higher than the unweighted signal-to-noise ratio.
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