Pyle-Pro PDMX4L 4 Channel Unbalanced 1/4'' To Balanced 1/4'' Mini Mixer Stereo/Mono Module Controlled By Module Switch - 4 Unbalanced Input Channels - 1 Balanced Output Channel - Separate Volume Controls Gain: 24db - Frequency Response: 10Hz ~ 100kHz Total Harmonic Distortion &lt; 0.05% - Max Output Level: +16dB (Balanced Output) Continuous Working (For More Than 12 Hours) 9V Battery Compartment - Power Supply: DC 12v (Not Included)