The latest upgrade: LM317 low ripple voltage regulator circuit design, preamplifier were used in a fever-class op amp OP275, Power input bridge reactor, can be AC and DC, DC input can be divided into positive and negative, so more convenient to use Dynamic microphone, electret microphone universal, a broader purpose JP1, JP2 Select the type of microphone for setting the pin: JP1, JP2 all the way, jumper plug is the working mode of the electret microphone, jumper cap plug is dynamic microphone mode of operation. Microphone reverberation chip using PT2399, microphone amplification, preamplifier respectively, using a fever class op amp OP275, microphone board two microphone volume can be independently controlled. Dynamic microphone, electret microphone can be universal. Board has MIC-1 volume, MIC-2 volume, reverberation times, reverb, external audio volume adjustment. Working voltage: AC: 6v-17v or DC: 12v-24v Colour:Red Material:plastic Size:100x50mm Package Contents: 4 x Audio Amplifier Board Only the above package content, other products are not included. Note: Light reflection 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.