To help you select a power amplifier, I am going to describe the term "signal-to-noise ratio" that is frequently used in order to express the performance of audio amplifiers.
As soon as you have selected a range of amps, it's time to explore some 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 essential spec and explains how much noise or hiss the amplifier creates.
Comparing the noise level of different amplifiers can be done quite easily. Just get together a couple of versions that you wish to compare and short circuit the inputs. Afterward put the amplifier gain to maximum and verify the level of static by listening to the speaker. You will hear some amount of hissing and/or hum coming from the loudspeaker. This hiss is produced by the amp itself. Ensure that the volume of the amplifiers is set to the same amount. Otherwise you will not be able to objectively compare the amount of static between different amplifiers. The general rule is: the lower the level of static that you hear the better the noise performance.
When looking at the amp specification sheet, you want to look for an amp with a large signal-to-noise ratio number which indicates that the amp outputs a low amount of static. Noise is produced due to several reasons. One reason is that today's amplifiers all employ elements including transistors plus resistors. Those elements will produce some amount of noise. Given that the amp overall noise performance is mostly determined by the performance of components located at the amplifier input, makers will attempt to choose low-noise components whilst developing the amplifier input stage.
Most of modern power amps are digital amplifiers, also referred to as "class-d amps". Class-D amps use a switching stage that oscillates at a frequency between 300 kHz to 1 MHz. Because of this, the output signal of switching amps have a moderately large level of switching noise. This noise component, however, is typically impossible to hear since it is well above 20 kHz. Though, it can still contribute to loudspeaker distortion. Signal-to-noise ratio is generally only shown within the range of 20 Hz to 20 kHz. Consequently, a lowpass filter is used while measuring switching amplifiers to remove the switching noise.
The signal-to-noise ratio is measured by feeding a 1 kHz test signal 60 dB underneath the full scale and measuring the noise floor of the amplifier. The amplification of the amp is set such that the full output wattage of the amplifier can be achieved. After that, only the hiss in the range of 20 Hz and 20 kHz is considered. The noise at other frequencies is removed through a filter. Next the amount of the noise energy in relation to the full-scale output power is calculated and shown in db.
Frequently the signal-to-noise ratio is shown in a more subjective way as "dbA" or "A weighted". In other words, this method tries to state how the noise is perceived by a person. Human hearing is most sensitive to signals around 1 kHz whereas signals under 50 Hz and higher than 14 kHz are hardly noticed. As a result an A-weighting filter will amplify the noise floor for frequencies which are easily perceived and suppress the noise floor at frequencies that are barely heard. Most amplifiers are going to have a higher A-weighted signal-to-noise ratio than the un-weighted ratio.
As soon as you have selected a range of amps, it's time to explore some 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 essential spec and explains how much noise or hiss the amplifier creates.
Comparing the noise level of different amplifiers can be done quite easily. Just get together a couple of versions that you wish to compare and short circuit the inputs. Afterward put the amplifier gain to maximum and verify the level of static by listening to the speaker. You will hear some amount of hissing and/or hum coming from the loudspeaker. This hiss is produced by the amp itself. Ensure that the volume of the amplifiers is set to the same amount. Otherwise you will not be able to objectively compare the amount of static between different amplifiers. The general rule is: the lower the level of static that you hear the better the noise performance.
When looking at the amp specification sheet, you want to look for an amp with a large signal-to-noise ratio number which indicates that the amp outputs a low amount of static. Noise is produced due to several reasons. One reason is that today's amplifiers all employ elements including transistors plus resistors. Those elements will produce some amount of noise. Given that the amp overall noise performance is mostly determined by the performance of components located at the amplifier input, makers will attempt to choose low-noise components whilst developing the amplifier input stage.
Most of modern power amps are digital amplifiers, also referred to as "class-d amps". Class-D amps use a switching stage that oscillates at a frequency between 300 kHz to 1 MHz. Because of this, the output signal of switching amps have a moderately large level of switching noise. This noise component, however, is typically impossible to hear since it is well above 20 kHz. Though, it can still contribute to loudspeaker distortion. Signal-to-noise ratio is generally only shown within the range of 20 Hz to 20 kHz. Consequently, a lowpass filter is used while measuring switching amplifiers to remove the switching noise.
The signal-to-noise ratio is measured by feeding a 1 kHz test signal 60 dB underneath the full scale and measuring the noise floor of the amplifier. The amplification of the amp is set such that the full output wattage of the amplifier can be achieved. After that, only the hiss in the range of 20 Hz and 20 kHz is considered. The noise at other frequencies is removed through a filter. Next the amount of the noise energy in relation to the full-scale output power is calculated and shown in db.
Frequently the signal-to-noise ratio is shown in a more subjective way as "dbA" or "A weighted". In other words, this method tries to state how the noise is perceived by a person. Human hearing is most sensitive to signals around 1 kHz whereas signals under 50 Hz and higher than 14 kHz are hardly noticed. As a result an A-weighting filter will amplify the noise floor for frequencies which are easily perceived and suppress the noise floor at frequencies that are barely heard. Most amplifiers are going to have a higher A-weighted signal-to-noise ratio than the un-weighted ratio.
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You can get additional information regarding power amplifier models as well as t amp models from Amphony's website.
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