Compact and battery powered mini mixer is simple to use with four 1/4 unbalanced input channels and a 1/4 master output volume control. Use with line level audio devices and dynamic microphones. Durable metal case. Up to 20 hours of use on new battery. Also includes a DC input plug (battery and power supply not included). SPECIFICATIONS MAX GAIN: 50dB INPUT IMPEDANCE: 4.5K ohm FREQUENCY RESPONSE: No less than + or - 1dB (20Hz-20KHz) THD: 108dB BATTERY: 9VDC CONTINUOUS WORKING TIME: >20 hours DIMENSION: 6 x 3.3 x 2