Boot annoying sound, The amplifier works without the current sound. Try to enter the wire is not clear. If there is noise / current beep, The noise signal will be amplified. The control off current is only 0.4 mA. Power per quiescent current 28mA. High gain amplification (36 dB). Very suitable for amplifying weak signals, eliminating the need to increase the preamp,Cut costs. The computer audio input amplifier should be changed to 20 dB using gain. With output short circuit protection. Troubleshooting will resume normal operation immediately. Various pins and product size are fully compatible. Colour: red Material: metal and ABS Package Contents: 2 * module Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.