piece of electronic audio equipment has a certain amount of operating noise
caused by random movement of electrons
(thermal noise) in its circuitry.
The difference between the level of this noise floor and the level of
the maximum signal the device can pass gives the signal to noise specification.
The higher the figure the quieter the operation of the device. A signal
to noise spec in excess of 90 db is very good.
should be taken to operate audio equipment so as to take advantage of the
available signal to noise specifications. This means
ensuring that the signal fed to the device is of a sufficiently high level.
To low a level will result in the noise floor of the device becoming audible.