To help you decide on an audio amplifier, I will clarify the expression "signal-to-noise ratio" which is frequently used in order to express the performance of audio amplifiers.
You can perform a simple assessment of the amp hiss by short circuiting the amplifier input, setting the gain to maximum and listening to a loudspeaker attached to the amp. The hiss that you hear is produced by the amp itself. After that compare several amplifiers according to the next rule: the smaller the level of noise, the higher the noise performance of the amp. On the other hand, bear in mind that you have to put all amplifiers to amplify by the same amount to compare different amps.
If you prefer an amp with a small level of hissing, you may look at the signal-to-noise ratio number of the data sheet. The majority of manufacturers are going to show this number. Amps with a high signal-to-noise ratio are going to output a small level of static. Noise is created due to several reasons. One factor is that today's amplifiers all utilize elements like transistors in addition to resistors. Those components are going to make some amount of noise. Mostly the elements that are situated at the input stage of an amp will contribute most to the overall hiss. Consequently suppliers typically will pick low-noise elements while designing the amp input stage.
A lot of latest power amps incorporate a power switching stage that switches at a frequency around 500 kHz. As a result, the output signal of switching amps have a rather big level of switching noise. This noise component, however, is usually impossible to hear since it is well above 20 kHz. However, it can 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 utilized while measuring switching amplifiers in order to eliminate the switching noise.
The majority of modern power amplifiers are digital amplifiers, also known as "class-d amplifiers". Class-D amps use a switching stage which oscillates at a frequency between 300 kHz to 1 MHz. Because of this, the output signal of switching amps have a fairly large level of switching noise. This noise component, however, is usually inaudible given that it is well above 20 kHz. Yet, it can still contribute to speaker distortion. Signal-to-noise ratio is usually only shown within the range of 20 Hz to 20 kHz. Consequently, a lowpass filter is utilized while measuring switching amplifiers in order to remove the switching noise. The most popular method for measuring the signal-to-noise ratio is to set the amplifier to a gain that permits the maximum output swing. After that a test tone is input to the amplifier. The frequency of this signal is generally 1 kHz. The amplitude of this tone is 60 dB underneath the full scale signal. Subsequently, the noise floor between 20 Hz and 20 kHz is measured and the ratio to the full-scale signal calculated. The noise signal at other frequencies is eliminated through a bandpass filter during this measurement.
Often you are going to find the term "dBA" or "a-weighted" in your amp parameter sheet. A weighting is a technique of showing the noise floor in a more subjective fashion. In other words, this technique attempts to state how the noise is perceived by a human. Human hearing is most perceptive to signals around 1 kHz while signals below 50 Hz and above 14 kHz are barely heard. The A-weighted signal-to-noise ratio is generally higher than the unweighted ratio and is shown in most amp specification sheets.
You can perform a simple assessment of the amp hiss by short circuiting the amplifier input, setting the gain to maximum and listening to a loudspeaker attached to the amp. The hiss that you hear is produced by the amp itself. After that compare several amplifiers according to the next rule: the smaller the level of noise, the higher the noise performance of the amp. On the other hand, bear in mind that you have to put all amplifiers to amplify by the same amount to compare different amps.
If you prefer an amp with a small level of hissing, you may look at the signal-to-noise ratio number of the data sheet. The majority of manufacturers are going to show this number. Amps with a high signal-to-noise ratio are going to output a small level of static. Noise is created due to several reasons. One factor is that today's amplifiers all utilize elements like transistors in addition to resistors. Those components are going to make some amount of noise. Mostly the elements that are situated at the input stage of an amp will contribute most to the overall hiss. Consequently suppliers typically will pick low-noise elements while designing the amp input stage.
A lot of latest power amps incorporate a power switching stage that switches at a frequency around 500 kHz. As a result, the output signal of switching amps have a rather big level of switching noise. This noise component, however, is usually impossible to hear since it is well above 20 kHz. However, it can 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 utilized while measuring switching amplifiers in order to eliminate the switching noise.
The majority of modern power amplifiers are digital amplifiers, also known as "class-d amplifiers". Class-D amps use a switching stage which oscillates at a frequency between 300 kHz to 1 MHz. Because of this, the output signal of switching amps have a fairly large level of switching noise. This noise component, however, is usually inaudible given that it is well above 20 kHz. Yet, it can still contribute to speaker distortion. Signal-to-noise ratio is usually only shown within the range of 20 Hz to 20 kHz. Consequently, a lowpass filter is utilized while measuring switching amplifiers in order to remove the switching noise. The most popular method for measuring the signal-to-noise ratio is to set the amplifier to a gain that permits the maximum output swing. After that a test tone is input to the amplifier. The frequency of this signal is generally 1 kHz. The amplitude of this tone is 60 dB underneath the full scale signal. Subsequently, the noise floor between 20 Hz and 20 kHz is measured and the ratio to the full-scale signal calculated. The noise signal at other frequencies is eliminated through a bandpass filter during this measurement.
Often you are going to find the term "dBA" or "a-weighted" in your amp parameter sheet. A weighting is a technique of showing the noise floor in a more subjective fashion. In other words, this technique attempts to state how the noise is perceived by a human. Human hearing is most perceptive to signals around 1 kHz while signals below 50 Hz and above 14 kHz are barely heard. The A-weighted signal-to-noise ratio is generally higher than the unweighted ratio and is shown in most amp specification sheets.
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