To help you select an audio amplifier, I am going to explain the expression "signal-to-noise ratio" which is frequently used in order to describe the performance of audio amplifiers.
As soon as you have chosen a number of amps, it's time to investigate a few of the specifications in more detail in order to help you narrow down your search to one model. The signal-to-noise ratio is a fairly vital specification and explains how much noise or hiss the amplifier produces.
One technique in order to perform a straightforward check of the noise performance of an amp is to short circuit the amp input and then to crank up the amplifier to its maximum. Next listen to the loudspeaker which you have connected. You are going to hear some amount of hissing and/or hum coming from the loudspeaker. This noise is produced by the amp itself. After that compare several amps according to the next rule: the lower the amount of static, the higher the noise performance of the amp. On the other hand, keep in mind that you should put all amps to amplify by the same level in order to compare different amplifiers. If you favor an amp with a small amount of hissing, you may look at the signal-to-noise ratio number of the spec sheet. Many suppliers are going to display this number. Amps with a large signal-to-noise ratio will output a low amount of static. There are several reasons why power amplifiers is going to add some form of hiss or other unwanted signal. Transistors and resistors that are part of every modern amplifier by nature generate noise. Generally the elements which are located at the input stage of an amplifier will contribute most to the overall hiss. Therefore makers generally will choose low-noise components when developing the amp input stage.
The majority of latest power amps are digital amplifiers, also known as "class-d amps". Class-D amps employ a switching stage which oscillates at a frequency between 300 kHz to 1 MHz. As a result, the output signal of switching amplifiers contain a rather large level of switching noise. This noise component, however, is generally inaudible because it is well above 20 kHz. Nonetheless, it can still contribute to speaker distortion. Signal-to-noise ratio is generally only shown within the range of 20 Hz to 20 kHz. As a result, a lowpass filter is utilized while measuring switching amplifiers to remove the switching noise.
Most of latest amplifiers are based on a digital switching architecture. They are called "class-D" or "class-T" amps. Switching amplifiers incorporate a power stage which is always switched at a frequency of approximately 400 kHz. This switching noise can result in some level of speaker distortion but is generally not included in the the signal-to-noise ratio which merely considers noise in the range of 20 Hz and 20 kHz. The most widespread method for measuring the signal-to-noise ratio is to set the amplifier to a gain that allows the maximum output swing. Next a test signal is fed to the amplifier. The frequency of this signal is usually 1 kHz. The amplitude of this signal is 60 dB underneath the full scale signal. Then, only the noise in the range of 20 Hz and 20 kHz is considered. The noise at other frequencies is eliminated by a filter. Then the amount of the noise energy in relation to the full-scale output wattage is calculated and shown in decibel.
Time and again you will find the expression "dBA" or "a-weighted" in your amplifier spec sheet. A weighting is a technique of showing the noise floor in a more subjective manner. This technique attempts to evaluate in how far the amp noise is perceived by human hearing which is most perceptive to signals at frequencies at 1 kHz. An A-weighted signal-to-noise ratio weighs the noise floor according to the human hearing and is typically higher than the unweighted signal-to-noise ratio.
As soon as you have chosen a number of amps, it's time to investigate a few of the specifications in more detail in order to help you narrow down your search to one model. The signal-to-noise ratio is a fairly vital specification and explains how much noise or hiss the amplifier produces.
One technique in order to perform a straightforward check of the noise performance of an amp is to short circuit the amp input and then to crank up the amplifier to its maximum. Next listen to the loudspeaker which you have connected. You are going to hear some amount of hissing and/or hum coming from the loudspeaker. This noise is produced by the amp itself. After that compare several amps according to the next rule: the lower the amount of static, the higher the noise performance of the amp. On the other hand, keep in mind that you should put all amps to amplify by the same level in order to compare different amplifiers. If you favor an amp with a small amount of hissing, you may look at the signal-to-noise ratio number of the spec sheet. Many suppliers are going to display this number. Amps with a large signal-to-noise ratio will output a low amount of static. There are several reasons why power amplifiers is going to add some form of hiss or other unwanted signal. Transistors and resistors that are part of every modern amplifier by nature generate noise. Generally the elements which are located at the input stage of an amplifier will contribute most to the overall hiss. Therefore makers generally will choose low-noise components when developing the amp input stage.
The majority of latest power amps are digital amplifiers, also known as "class-d amps". Class-D amps employ a switching stage which oscillates at a frequency between 300 kHz to 1 MHz. As a result, the output signal of switching amplifiers contain a rather large level of switching noise. This noise component, however, is generally inaudible because it is well above 20 kHz. Nonetheless, it can still contribute to speaker distortion. Signal-to-noise ratio is generally only shown within the range of 20 Hz to 20 kHz. As a result, a lowpass filter is utilized while measuring switching amplifiers to remove the switching noise.
Most of latest amplifiers are based on a digital switching architecture. They are called "class-D" or "class-T" amps. Switching amplifiers incorporate a power stage which is always switched at a frequency of approximately 400 kHz. This switching noise can result in some level of speaker distortion but is generally not included in the the signal-to-noise ratio which merely considers noise in the range of 20 Hz and 20 kHz. The most widespread method for measuring the signal-to-noise ratio is to set the amplifier to a gain that allows the maximum output swing. Next a test signal is fed to the amplifier. The frequency of this signal is usually 1 kHz. The amplitude of this signal is 60 dB underneath the full scale signal. Then, only the noise in the range of 20 Hz and 20 kHz is considered. The noise at other frequencies is eliminated by a filter. Then the amount of the noise energy in relation to the full-scale output wattage is calculated and shown in decibel.
Time and again you will find the expression "dBA" or "a-weighted" in your amplifier spec sheet. A weighting is a technique of showing the noise floor in a more subjective manner. This technique attempts to evaluate in how far the amp noise is perceived by human hearing which is most perceptive to signals at frequencies at 1 kHz. An A-weighted signal-to-noise ratio weighs the noise floor according to the human hearing and is typically higher than the unweighted signal-to-noise ratio.
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