1）Check whether the input-output interface is connected correctly. The upper row of the back panel is the input, and the lower row is the output. Every three pins from left to right represent a channel.
2）Check whether the channel corresponding to the mixer is open.
3）Check whether there is sound in the input source, and use line input test.
4）Check the parameters of the front voltage limit and the back voltage limit. If the level or ratio is too high or the gain is too small, the sound will be small or even inaudible.
5）Check the mute parameters and corresponding level values of the input and output channels.
6）Check whether the frequency parameter setting of the frequency divider is correct. In this version, it is band-pass, and in the band-stop state, all sounds in the frequency band will be shielded.