Working voltage: DC3.7V-15V Ultra-small dynamic microphone preamplifier board, two-channel design, suitable for a single lithium battery powered, with AD828 fever operational amplifier chip, suitable for low-voltage power supply (3.7-15V) Note: This microphone preamplifier board without voltage regulator circuit, can only use the battery or linear power supply, cannot use switching power supply, otherwise there will be interference. If you only use one channel, the other channel must short the input with GND, to avoid interference with signal crosstalk. Size: 3.2x2cm/1.3x0.79inch Note: Please allow 1-3mm error due to manual measurement. Make sure you don't mind before bidding. Due to the difference between different monitors, the picture may not reflect the actual color of the item. Thank you! Packing list: 1x AD828 Stereo Dynamic Microphone Preamplifier Board