It is easy to be confused by the language that amplifier producers employ to explain the performance of their products. I am going to explain the meaning of a frequently used amp parameter: "signal-to-noise ratio" to help you make an informed decision while purchasing a brand new amplifier.
You can make a straightforward comparison of the amp noise by short circuiting the amp input, setting the volume to maximum and listening to a loudspeaker attached to the amp. You are going to hear some amount of hissing and/or hum coming from the speaker. This hiss is created by the amplifier itself. Make sure that the volume of the amps is set to the same amount. Otherwise you will not be able to objectively compare the level of static between different amplifiers. The general rule is: the smaller the amount of hiss which you hear the better the noise performance.
A method to do a straightforward test of the noise performance of an amplifier is to short circuit the amplifier input and then to crank up the amp to its utmost. Subsequently listen to the loudspeaker which you have attached. You are going to hear some amount of hissing and/or hum coming from the speaker. This noise is generated by the amplifier itself. Make sure that the volume of the amps is set to the same amount. Otherwise you will not be able to objectively evaluate the amount of hiss between different amplifiers. The general rule is: the smaller the amount of hiss that you hear the better the noise performance.
Many recent power amps include a wattage switching stage which switches at a frequency around 500 kHz. This switching noise can cause some level of speaker distortion yet is typically not included in the the signal-to-noise ratio which only considers noise between 20 Hz and 20 kHz.
Manufacturers measure the signal-to-noise ratio by setting the amplifier such that the full output swing can be achieved and by inputting a test tone to the amplifier that is generally 60 dB underneath the full scale of the amp. Next, 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 removed via a bandpass filter during this measurement.
Frequently the signal-to-noise ratio is shown in a more subjective method as "dbA" or "A weighted". This technique was developed with the knowledge that human hearing perceives noise at different frequencies differently. Human hearing is most responsive to signals around 1 kHz. However, signals below 50 Hz and higher than 13 kHz are barely heard. Thus an A-weighting filter is going to amplify the noise floor for frequencies which are easily heard and suppress the noise floor at frequencies that are barely noticed. Many amps will show a higher A-weighted signal-to-noise ratio than the un-weighted ratio.
You can make a straightforward comparison of the amp noise by short circuiting the amp input, setting the volume to maximum and listening to a loudspeaker attached to the amp. You are going to hear some amount of hissing and/or hum coming from the speaker. This hiss is created by the amplifier itself. Make sure that the volume of the amps is set to the same amount. Otherwise you will not be able to objectively compare the level of static between different amplifiers. The general rule is: the smaller the amount of hiss which you hear the better the noise performance.
A method to do a straightforward test of the noise performance of an amplifier is to short circuit the amplifier input and then to crank up the amp to its utmost. Subsequently listen to the loudspeaker which you have attached. You are going to hear some amount of hissing and/or hum coming from the speaker. This noise is generated by the amplifier itself. Make sure that the volume of the amps is set to the same amount. Otherwise you will not be able to objectively evaluate the amount of hiss between different amplifiers. The general rule is: the smaller the amount of hiss that you hear the better the noise performance.
Many recent power amps include a wattage switching stage which switches at a frequency around 500 kHz. This switching noise can cause some level of speaker distortion yet is typically not included in the the signal-to-noise ratio which only considers noise between 20 Hz and 20 kHz.
Manufacturers measure the signal-to-noise ratio by setting the amplifier such that the full output swing can be achieved and by inputting a test tone to the amplifier that is generally 60 dB underneath the full scale of the amp. Next, 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 removed via a bandpass filter during this measurement.
Frequently the signal-to-noise ratio is shown in a more subjective method as "dbA" or "A weighted". This technique was developed with the knowledge that human hearing perceives noise at different frequencies differently. Human hearing is most responsive to signals around 1 kHz. However, signals below 50 Hz and higher than 13 kHz are barely heard. Thus an A-weighting filter is going to amplify the noise floor for frequencies which are easily heard and suppress the noise floor at frequencies that are barely noticed. Many amps will show a higher A-weighted signal-to-noise ratio than the un-weighted ratio.
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