It is easy to be confused by the language which amp producers employ in order to express the performance of their models. I am going to explain the meaning of a regularly utilized amplifier parameter: "signal-to-noise ratio" to help you make an informed choice while purchasing a new amp.

You can perform a simple comparison of the amplifier noise by short circuiting the amp input, setting the gain to maximum and listening to a loudspeaker connected to the amplifier. Usually you are going to hear 2 components. The first is hissing. In addition, you will regularly hear a hum at 50 or 60 Hz. Both of these are components which are generated by the amplifier itself. Be certain that the volume of the amps is set to the same amount. Otherwise you will not be able to objectively evaluate the amount of static between several amps. The general rule is: the lower the level of hiss which you hear the higher the noise performance.

Comparing the noise level of several amplifiers may be accomplished rather easily. Just gather a couple of types that you want to compare and short circuit the inputs. Then put the amplifier gain to maximum and verify the level of hiss by listening to the speaker. You will hear some amount of hissing and/or hum coming from the speaker. This hiss is created 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 compare the amount of noise between different amps. The general rule is: the lower the amount of noise that you hear the higher the noise performance. To help you compare the noise performance, amp producers publish the signal-to-noise ratio in their amplifier spec sheets. Simply put, the larger the signal-to-noise ratio, the smaller the amount of noise the amp produces. Noise is generated due to a number of factors. One factor is that modern amplifiers all employ elements including transistors along with resistors. These elements are going to create some amount of hiss. The overall noise is dependent on how much noise each element creates. However, the location of these components is also important. Elements which are part of the amp input stage will usually contribute most of the noise.

Whilst taking a look at the amp specification sheet, you want to look for an amplifier with a large signal-to-noise ratio number which indicates that the amplifier outputs a low level of static. One of the reasons why amplifiers make noise is the fact that they use components including transistors and resistors that by nature produce noise. Given that the amplifier overall noise performance is mostly determined by the performance of elements situated at the amplifier input, manufacturers are going to try to select low-noise parts while developing the amplifier input stage.

Makers measure the signal-to-noise ratio by setting the amplifier such that the full output swing can be realized and by feeding a test signal to the amp which is generally 60 dB underneath the full scale of the amplifier. Subsequently, the noise floor between 20 Hz and 20 kHz is calculated and the ratio to the full-scale signal computed. The noise signal at other frequencies is removed through a bandpass filter throughout this measurement.

A different convention in order to state the signal-to-noise ratio uses more subjective terms. These terms are "dBA" or "A weighted". You will spot these terms in most amplifier specification sheets. In other words, this technique tries to express how the noise is perceived by a person. Human hearing is most perceptive to signals around 1 kHz while signals under 50 Hz and higher than 14 kHz are hardly heard. An A-weighted signal-to-noise ratio weighs the noise floor according to the human hearing and is normally larger than the unweighted signal-to-noise ratio.