The board uses the PT2399 built-in chip to return to sound processing, and the setting is the four amp field effect opTL074 for audio signal amplification and sound processing. Also added a new 5V output, can be connected to the USB Bluetooth decoder board, more convenient to use. In addition, the karaoke card also uses a two-way microphone input (compatible with electret microphone) Working voltage: Double AC12 - 15V Colour: green Material: plastic Size: 157x88mm Package Contents: 1 x Microphone Amplifier Tone Board NOTE: This is the front tuning card of the amplifier. Need to be equipped with a post amplifier to use. If you contact for the first time, you might not understand, This card is set up with a station amplifier and has no audio output. You need to match a post amplifier. Just import the signal from the preamp. Pre-tuning signal-input post-amplifier-post-amplifier pushes signal processing to the speaker 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.