Are you looking to get a new power amplifier model for your home speakers? You might be dazzled by the number of options you have. In order to make an informed selection, it is best to familiarize yourself with frequent terms. One of these specs is named “signal-to-noise ratio” and is not frequently understood. I will help explain the meaning of this expression.
As soon as you have chosen a range of amps, it’s time to investigate a few of the specs in more detail to help you narrow down your search to one model. One important criterion of power amplifiers is the signal-to-noise ratio. To put it simply, the signal-to-noise ratio explains how much hum or hiss the amplifier is going to add to the audio signal. This ratio is generally described in decibel or “db” for short.
Comparing the noise level of several amps may be accomplished rather easily. Just get together a number of models that you wish to compare and short circuit the inputs. After that set the amplifier volume to maximum and check the level of hiss by listening to the speaker. Usually you are going to hear two components. The first is hissing. In addition, you are going to frequently hear a hum at 50 or 60 Hz. Both of these are components which are created by the amp itself. Make certain that the gain of the amplifiers is set to the same level. Otherwise you will not be able to objectively evaluate the level of noise between different amps. The general rule is: the smaller the level of noise which you hear the better the noise performance.
Whilst looking at the amp specification sheet, you want to look for an amp with a high signal-to-noise ratio number which suggests that the amplifier outputs a low amount of noise. Noise is produced due to a number of factors. One reason is that modern amplifiers all employ components such as transistors plus resistors. These elements are going to produce some amount of hiss. Because the amp overall noise performance is mostly determined by the performance of elements situated at the amp input, suppliers are going to try to choose low-noise parts while designing the amp input stage.
A lot of latest power amps incorporate a power switching stage that switches at a frequency around 500 kHz. As a result, the output signal of switching amplifiers exhibit a moderately large level of switching noise. This noise component, however, is generally inaudible because it is well above 20 kHz. However, it may still contribute to speaker distortion. Signal-to-noise ratio is usually only shown within the range of 20 Hz to 20 kHz. Consequently, a lowpass filter is used while measuring switching amplifiers in order to remove the switching noise.
The most widespread technique for measuring the signal-to-noise ratio is to set the amp to a gain which enables the maximum output swing. Subsequently a test tone is fed to the amplifier. The frequency of this signal is generally 1 kHz. The amplitude of this tone is 60 dB underneath the full scale signal. 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 through a bandpass filter throughout this measurement.
One more convention to state the signal-to-noise ratio utilizes more subjective terms. These terms are “dBA” or “A weighted”. You will spot these terms in many amp parameter sheets. In other words, this technique attempts to express how the noise is perceived by a human. Human hearing is most perceptive to signals around 1 kHz while signals under 50 Hz and higher than 14 kHz are hardly heard. The A-weighted signal-to-noise ratio is typically higher than the unweighted ratio and is published in the majority of amplifier parameter sheets.