CM-839MiniPortable Amplifiers (with radio, USB) Performance parameters Output power: 25WCharging voltage: 12V, 450mAPolar pattern: cardioidFrequency response: 100Hz-10KHz ± 3dBPower supply: 7.4V, 2000mA, Lithium BatteryDimension: 125 × 55 × 87mmMicrophone Sensitivity: -53 ± 3dB