Background Noise?
Answer: Disconnect the input cable of the amplifier and turn up the sound to the full position, then you can verify if noise is from the amplifier or the sound source itself.
Noise in output?
Answer: Firstly, please try to play another song and check if the noise is within the song itself; secondly, check if the cables are connected firmly; lastly, check if the front-end output signal is of standard 2.0 Vrms, if it is over this data, the amplifier output will make noise.