It is easy to be bewildered by the language which amp manufacturers use in order to express the performance of their models. I will explain the meaning of one regularly used amp parameter: "signal-to-noise ratio" to help you make an informed decision when purchasing a new amp.
As soon as you have narrowed down your search by taking a look at some fundamental criteria, such as the level of output wattage, the size of the amp and the cost, you will 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. An important criterion of power amps is the signal-to-noise ratio. To put it simply, the signal-to-noise ratio shows how much hum or hiss the amp is going to add to the audio signal. This ratio is customarily described in decibel or "db" for short.
Comparing the noise level of several amps can be done fairly easily. Just get together several models that you wish to evaluate and short circuit the inputs. After that put the amplifier volume to maximum and check the level of static by listening to the speaker. Typically you are going to hear two components. The first is hissing. In addition, you are going to regularly hear a hum at 50 or 60 Hz. Both of these are components which are created by the amplifier itself. Ensure that the gain of the amplifiers is set to the same amount. Otherwise you will not be able to objectively evaluate the amount of static between different amps. The general rule is: the lower the level of static which you hear the better the noise performance.
The majority of of today's amplifiers are based on a digital switching architecture. They are known as "class-D" or "class-T" amps. Switching amps include a power stage which is always switched at a frequency of approximately 400 kHz. This switching frequency is also noise that is part of the amplified signal. Yet, today's amp specs generally only consider the hiss between 20 Hz and 20 kHz.
Makers measure the signal-to-noise ratio by means of setting the amp such that the full output swing may be realized and by inputting a test signal to the amp which is typically 60 dB underneath the full scale of the amplifier. Next, the noise floor between 20 Hz and 20 kHz is calculated and the ratio to the full-scale signal computed. The noise signal at different frequencies is eliminated through a bandpass filter throughout this measurement.
A different convention in order to state the signal-to-noise ratio makes use of more subjective terms. These terms are "dBA" or "A weighted". You are going to spot these terms in a lot of amp specification sheets. 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 higher than 14 kHz are hardly heard. For that reason an A-weighting filter will amplify the noise floor for frequencies that are easily perceived and suppress the noise floor at frequencies which are barely noticed. A lot of amps will have a larger A-weighted signal-to-noise ratio than the un-weighted ratio.
As soon as you have narrowed down your search by taking a look at some fundamental criteria, such as the level of output wattage, the size of the amp and the cost, you will 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. An important criterion of power amps is the signal-to-noise ratio. To put it simply, the signal-to-noise ratio shows how much hum or hiss the amp is going to add to the audio signal. This ratio is customarily described in decibel or "db" for short.
Comparing the noise level of several amps can be done fairly easily. Just get together several models that you wish to evaluate and short circuit the inputs. After that put the amplifier volume to maximum and check the level of static by listening to the speaker. Typically you are going to hear two components. The first is hissing. In addition, you are going to regularly hear a hum at 50 or 60 Hz. Both of these are components which are created by the amplifier itself. Ensure that the gain of the amplifiers is set to the same amount. Otherwise you will not be able to objectively evaluate the amount of static between different amps. The general rule is: the lower the level of static which you hear the better the noise performance.
The majority of of today's amplifiers are based on a digital switching architecture. They are known as "class-D" or "class-T" amps. Switching amps include a power stage which is always switched at a frequency of approximately 400 kHz. This switching frequency is also noise that is part of the amplified signal. Yet, today's amp specs generally only consider the hiss between 20 Hz and 20 kHz.
Makers measure the signal-to-noise ratio by means of setting the amp such that the full output swing may be realized and by inputting a test signal to the amp which is typically 60 dB underneath the full scale of the amplifier. Next, the noise floor between 20 Hz and 20 kHz is calculated and the ratio to the full-scale signal computed. The noise signal at different frequencies is eliminated through a bandpass filter throughout this measurement.
A different convention in order to state the signal-to-noise ratio makes use of more subjective terms. These terms are "dBA" or "A weighted". You are going to spot these terms in a lot of amp specification sheets. 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 higher than 14 kHz are hardly heard. For that reason an A-weighting filter will amplify the noise floor for frequencies that are easily perceived and suppress the noise floor at frequencies which are barely noticed. A lot of amps will have a larger A-weighted signal-to-noise ratio than the un-weighted ratio.
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