Are you looking to acquire a new amp for your home speakers? You may be dazzled by the number of choices you have. In order to make an informed selection, it is best to familiarize yourself with popular terms. One of these specifications is named "signal-to-noise ratio" and is not frequently understood. I will help explain the meaning of this term.
You can perform a simple comparison of the amplifier hiss by short circuiting the amp input, setting the gain to maximum and listening to a speaker connected to the amp. 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. Then compare several amplifiers according to the following rule: the lower the amount of hiss, the higher the noise performance of the amp. Though, keep in mind that you should put all amps to amplify by the same level to evaluate different amps.
To help you evaluate the noise performance, amp producers publish the signal-to-noise ratio in their amp spec sheets. Simply put, the larger the signal-to-noise ratio, the smaller the amount of noise the amplifier produces. There are numerous reasons why power amps will add some form of noise or other unwanted signal. Transistors and resistors which are part of each modern amp by nature produce noise. Mostly the components which are situated at the input stage of an amplifier are going to contribute most to the overall noise. Therefore suppliers generally are going to select low-noise components whilst developing the amp input stage.
Most of today's amps are based on a digital switching topology. They are referred to as "class-D" or "class-T" amps. Switching amps include a power stage that is constantly switched at a frequency of approximately 400 kHz. This switching frequency is also noise which is part of the amplified signal. Nonetheless, latest amplifier specifications typically only consider the hiss between 20 Hz and 20 kHz.
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 gain of the amp is set such that the full output wattage of the amp can be realized. Then the noise-floor energy is measured in the frequency range between 20 Hz and 20 kHz and compared with the full scale signal energy.
Often the signal-to-noise ratio is expressed in a more subjective manner as "dbA" or "A weighted". In other words, this technique tries to state how the noise is perceived by a human. Human hearing is most sensitive to signals around 1 kHz whereas signals below 50 Hz and higher than 14 kHz are hardly heard. Therefore an A-weighting filter is going to amplify the noise floor for frequencies which are easily heard and suppress the noise floor at frequencies which are hardly noticed. Most amplifiers are going to have a higher A-weighted signal-to-noise ratio than the un-weighted ratio.
You can perform a simple comparison of the amplifier hiss by short circuiting the amp input, setting the gain to maximum and listening to a speaker connected to the amp. 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. Then compare several amplifiers according to the following rule: the lower the amount of hiss, the higher the noise performance of the amp. Though, keep in mind that you should put all amps to amplify by the same level to evaluate different amps.
To help you evaluate the noise performance, amp producers publish the signal-to-noise ratio in their amp spec sheets. Simply put, the larger the signal-to-noise ratio, the smaller the amount of noise the amplifier produces. There are numerous reasons why power amps will add some form of noise or other unwanted signal. Transistors and resistors which are part of each modern amp by nature produce noise. Mostly the components which are situated at the input stage of an amplifier are going to contribute most to the overall noise. Therefore suppliers generally are going to select low-noise components whilst developing the amp input stage.
Most of today's amps are based on a digital switching topology. They are referred to as "class-D" or "class-T" amps. Switching amps include a power stage that is constantly switched at a frequency of approximately 400 kHz. This switching frequency is also noise which is part of the amplified signal. Nonetheless, latest amplifier specifications typically only consider the hiss between 20 Hz and 20 kHz.
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 gain of the amp is set such that the full output wattage of the amp can be realized. Then the noise-floor energy is measured in the frequency range between 20 Hz and 20 kHz and compared with the full scale signal energy.
Often the signal-to-noise ratio is expressed in a more subjective manner as "dbA" or "A weighted". In other words, this technique tries to state how the noise is perceived by a human. Human hearing is most sensitive to signals around 1 kHz whereas signals below 50 Hz and higher than 14 kHz are hardly heard. Therefore an A-weighting filter is going to amplify the noise floor for frequencies which are easily heard and suppress the noise floor at frequencies which are hardly noticed. Most amplifiers are going to have a higher A-weighted signal-to-noise ratio than the un-weighted ratio.
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