... machine has an adjustable gain design. When the switch 1 and 2 in the OFF state, a gain of 0dB ... ; when switch 1 is ON and 2 is OFF, a gain of 10DB; 1 and 2 switch is ON, ... the largest 16DB gain. The two groups 1 and 2 switch the left and right channels of the amplifier module, ... , in particular, to increase the output gain adjustment switch, you can push a variety of sensitivity headphones, ...