I am going to clarify the meaning of one frequently utilized amplifier spec: “signal-to-noise ratio” to help you make an informed decision whilst purchasing a new amp.
Once you have narrowed down your search by looking at a few basic criteria, including the level of output power, the size of the amplifier and the cost, you are going to still have quite a few products to choose from. The signal-to-noise ratio is a rather key spec and explains how much noise or hiss the amp creates. Subsequently listen to the loudspeaker which you have attached. In addition, you are going to frequently hear a hum at 50 or 60 Hz. Yet, keep in mind that you must put all small stereo amps to amplify by the same amount in order to evaluate different amps. If you prefer an amp with a small level of hissing, you may look at the signal-to-noise ratio number of the data sheet. Most of latest power amplifiers are digital amps, also known as “class-d amps”. However, recent amp specs generally only consider the noise between 20 Hz and 20 kHz.
The signal-to-noise ratio is measured by inputting a 1 kHz test signal 60 dB underneath the full scale and measuring the noise floor of the amp. Then the noise-floor energy is measured in the frequency range between 20 Hz and 20 kHz and compared with the full scale signal energy.
You will spot these terms in many amp parameter sheets.