It is easy to be confused by the language that amplifier manufacturers utilize to describe the performance of their products. I am going to clarify the meaning of a usually used amp specification: "signal-to-noise ratio" to help you make an informed decision when buying a new amplifier.
Once you have narrowed down your search by taking a look at some fundamental criteria, including the amount of output power, the dimensions of the amp plus the price, you are going to still have quite a few models to choose from. Now it is time to take a look at some of the technical specs in more detail. Each amplifier will create a certain level of hiss as well as hum. The signal-to-noise ratio is going to help compute the level of noise generated by the amp.
Comparing the noise level of different amps can be accomplished quite easily. Just gather a couple of versions which you wish to compare and short circuit the inputs. Next put the amplifier gain to maximum and verify the amount of static by listening to the loudspeaker. You are going to hear some amount of hissing and/or hum coming from the loudspeaker. This noise is produced by the amplifier itself. Ensure that the gain of the amps is set to the same amount. Otherwise you will not be able to objectively evaluate the level of hiss between different amplifiers. The general rule is: the smaller the level of noise which you hear the higher the noise performance.
Most of modern power amps are digital amplifiers, also known as "class-d amps". Class-D amplifiers use a switching stage that oscillates at a frequency between 300 kHz to 1 MHz. In consequence, the output signal of switching amps have a fairly large level of switching noise. This noise component, however, is generally inaudible as 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. For that reason, a lowpass filter is used while measuring switching amplifiers to eliminate the switching noise.
The signal-to-noise ratio is measured by inputting a 1 kHz test tone 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 amp can be achieved. Next, the noise floor between 20 Hz and 20 kHz is measured and the ratio to the full-scale signal computed. The noise signal at other frequencies is removed through a bandpass filter during this measurement.
Frequently 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 way. In other words, this method tries to express how the noise is perceived by a person. Human hearing is most perceptive to signals around 1 kHz while signals below 50 Hz and above 14 kHz are hardly noticed. The A-weighted signal-to-noise ratio is frequently larger than the unweighted ratio and is shown in a lot of amp spec sheets.
Once you have narrowed down your search by taking a look at some fundamental criteria, including the amount of output power, the dimensions of the amp plus the price, you are going to still have quite a few models to choose from. Now it is time to take a look at some of the technical specs in more detail. Each amplifier will create a certain level of hiss as well as hum. The signal-to-noise ratio is going to help compute the level of noise generated by the amp.
Comparing the noise level of different amps can be accomplished quite easily. Just gather a couple of versions which you wish to compare and short circuit the inputs. Next put the amplifier gain to maximum and verify the amount of static by listening to the loudspeaker. You are going to hear some amount of hissing and/or hum coming from the loudspeaker. This noise is produced by the amplifier itself. Ensure that the gain of the amps is set to the same amount. Otherwise you will not be able to objectively evaluate the level of hiss between different amplifiers. The general rule is: the smaller the level of noise which you hear the higher the noise performance.
Most of modern power amps are digital amplifiers, also known as "class-d amps". Class-D amplifiers use a switching stage that oscillates at a frequency between 300 kHz to 1 MHz. In consequence, the output signal of switching amps have a fairly large level of switching noise. This noise component, however, is generally inaudible as 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. For that reason, a lowpass filter is used while measuring switching amplifiers to eliminate the switching noise.
The signal-to-noise ratio is measured by inputting a 1 kHz test tone 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 amp can be achieved. Next, the noise floor between 20 Hz and 20 kHz is measured and the ratio to the full-scale signal computed. The noise signal at other frequencies is removed through a bandpass filter during this measurement.
Frequently 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 way. In other words, this method tries to express how the noise is perceived by a person. Human hearing is most perceptive to signals around 1 kHz while signals below 50 Hz and above 14 kHz are hardly noticed. The A-weighted signal-to-noise ratio is frequently larger than the unweighted ratio and is shown in a lot of amp spec sheets.
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