What Is The Signal-To-Noise Ratio Of An Amplifier?

The signal-to-noise ratio (S/N) of a power amplifier is one of the key parameters that characterize its audio performance

It describes the degree of reproduction of audio in terms of distortion and reduces it through low noise background. The signal-to-noise ratio (S/N) is related to electronic components (such as transistors), depending on their usage location and the loading methods of their inputs and outputs. In some cases, the signal-to-noise ratio of a power amplifier can be improved by simply adding a virtual resistor from the source to the output. According to the S/N formula, the noise power is proportional to the square root of the bandwidth, which means it is more important in low frequencies with smaller margin. In other words, noise levels become important below -3dB. The lower cutoff point depends on input sensitivity and output impedance, as these two factors determine the voltage swing on the amplifier.

You should know that the rated maximum power is different from the power you can obtain on the speaker

Of course, this is not related to the signal-to-noise ratio S/N, but it is worth noting that most amplifiers cannot provide their full power to a 4-ohm load, which is the most common type of speaker. To determine which amplifier is most suitable for your situation, you must decide how much output power you need. For example, if you are listening at a moderate volume in a small room, an entry-level solid-state amplifier is sufficient. But if you have a larger space or are considering using more powerful speakers (speakers with a maximum sound pressure level greater than 105dB), you should consider a high-power model amplifier. It is also worth mentioning that in order to achieve better signal-to-noise ratio S/N, the amplifier must operate in Class A until its output reaches half of the maximum voltage swing or current. Afterwards, it should switch to AB mode, as the S/N will decrease by approximately 6dB due to higher division distortion.

Therefore, looking for a solid-state power amplifier

Try to avoid models with a rated signal-to-noise ratio below 85dB, as they may not fully utilize their potential when used with speakers. When purchasing amplifiers with higher ratings (above 90 dB), please do not pay too much attention to the numbers, but check the actual audio quality.