To help you choose an audio amplifier, I am going to describe the expression "signal-to-noise ratio" that is regularly used to express the performance of audio amplifiers.
One method in order to accomplish a simple assessment 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 which you have attached. You are going to hear some amount of hissing and/or hum coming from the loudspeaker. This hiss is produced by the amp itself. After that compare several amplifiers according to the following rule: the smaller the level of hiss, the higher the noise performance of the amp. However, keep in mind that you must put all amplifiers to amplify by the same amount to evaluate several amps.
If you prefer an amplifier with a small level of hissing, you may look at the signal-to-noise ratio figure of the specification sheet. Most makers are going to publish this figure. Amps with a high signal-to-noise ratio are going to output a small level of noise. One of the reasons why amps produce noise is the fact that they utilize components including transistors as well as resistors that by nature produce noise. The overall noise depends on how much hiss every component generates. However, the location of those components is also vital. Components which are part of the amplifier input stage will generally contribute most of the noise.
Many of latest amps are based on a digital switching architecture. They are called "class-D" or "class-T" amplifiers. Switching amps incorporate a power stage that is always switched at a frequency of approximately 400 kHz. Because of this, the output signal of switching amplifiers contain a rather large level of switching noise. This noise component, however, is usually impossible to hear because it is well above 20 kHz. On the other hand, it can still contribute to loudspeaker distortion. Signal-to-noise ratio is typically only shown within the range of 20 Hz to 20 kHz. As a result, a lowpass filter is utilized when measuring switching amps to eliminate the switching noise.
Most of today's power amps are digital amps, also known as "class-d amplifiers". Class-D amplifiers employ a switching stage which oscillates at a frequency between 300 kHz to 1 MHz. Consequently, the output signal of switching amplifiers contain a fairly large amount of switching noise. This noise component, however, is generally impossible to hear since it is well above 20 kHz. Yet, it may still contribute to loudspeaker distortion. Signal-to-noise ratio is usually only shown within the range of 20 Hz to 20 kHz. Thus, a lowpass filter is used while measuring switching amps to eliminate the switching noise. The signal-to-noise ratio is measured by feeding a 1 kHz test signal 60 dB below the full scale and measuring the noise floor of the amplifier. The amplification of the amp is set such that the full output power of the amp can be realized. Subsequently, the noise floor between 20 Hz and 20 kHz is calculated and the ratio to the full-scale signal computed. The noise signal at other frequencies is eliminated by a bandpass filter during this measurement.
Time and again you will find the expression "dBA" or "a-weighted" in your amp parameter sheet. A weighting is a technique of showing the noise floor in a more subjective manner. This method was designed with the knowledge that human hearing perceives noise at different frequencies differently. Human hearing is most sensitive to signals around 1 kHz. Though, signals below 50 Hz and higher than 13 kHz are hardly noticed. An A-weighted signal-to-noise ratio weighs the noise floor according to the human hearing and is typically larger than the unweighted signal-to-noise ratio.
One method in order to accomplish a simple assessment 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 which you have attached. You are going to hear some amount of hissing and/or hum coming from the loudspeaker. This hiss is produced by the amp itself. After that compare several amplifiers according to the following rule: the smaller the level of hiss, the higher the noise performance of the amp. However, keep in mind that you must put all amplifiers to amplify by the same amount to evaluate several amps.
If you prefer an amplifier with a small level of hissing, you may look at the signal-to-noise ratio figure of the specification sheet. Most makers are going to publish this figure. Amps with a high signal-to-noise ratio are going to output a small level of noise. One of the reasons why amps produce noise is the fact that they utilize components including transistors as well as resistors that by nature produce noise. The overall noise depends on how much hiss every component generates. However, the location of those components is also vital. Components which are part of the amplifier input stage will generally contribute most of the noise.
Many of latest amps are based on a digital switching architecture. They are called "class-D" or "class-T" amplifiers. Switching amps incorporate a power stage that is always switched at a frequency of approximately 400 kHz. Because of this, the output signal of switching amplifiers contain a rather large level of switching noise. This noise component, however, is usually impossible to hear because it is well above 20 kHz. On the other hand, it can still contribute to loudspeaker distortion. Signal-to-noise ratio is typically only shown within the range of 20 Hz to 20 kHz. As a result, a lowpass filter is utilized when measuring switching amps to eliminate the switching noise.
Most of today's power amps are digital amps, also known as "class-d amplifiers". Class-D amplifiers employ a switching stage which oscillates at a frequency between 300 kHz to 1 MHz. Consequently, the output signal of switching amplifiers contain a fairly large amount of switching noise. This noise component, however, is generally impossible to hear since it is well above 20 kHz. Yet, it may still contribute to loudspeaker distortion. Signal-to-noise ratio is usually only shown within the range of 20 Hz to 20 kHz. Thus, a lowpass filter is used while measuring switching amps to eliminate the switching noise. The signal-to-noise ratio is measured by feeding a 1 kHz test signal 60 dB below the full scale and measuring the noise floor of the amplifier. The amplification of the amp is set such that the full output power of the amp can be realized. Subsequently, the noise floor between 20 Hz and 20 kHz is calculated and the ratio to the full-scale signal computed. The noise signal at other frequencies is eliminated by a bandpass filter during this measurement.
Time and again you will find the expression "dBA" or "a-weighted" in your amp parameter sheet. A weighting is a technique of showing the noise floor in a more subjective manner. This method was designed with the knowledge that human hearing perceives noise at different frequencies differently. Human hearing is most sensitive to signals around 1 kHz. Though, signals below 50 Hz and higher than 13 kHz are hardly noticed. An A-weighted signal-to-noise ratio weighs the noise floor according to the human hearing and is typically larger than the unweighted signal-to-noise ratio.
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