4 Channel USB Bluetooth Audio Mixer.    Feature: - Can connect wired/wireless/capacitor microphone, applicable to the family KTV, campus speech, meeting etc.  - Built in reverb effect, by adjusting knob to adjust the reverb depth and delay effect.  - USB/MP3 Jack, USB Jack can be connected to U disk or MP3 and other portable audio equipment.  - You can call up professional audio.  - 3 stage equalization regulate,by adjusting knob to adjust the reverb depth and delay effect.  - Two sets of stereo output, one earphone monitor and one auxiliary effect output.  - There are 6 modes of music: nature, rock, jazz, classical, Soft, Mega bass.  - Bluetooth access in one second. Built-in Bluetooth function to support wireless docking of most Bluetooth-enabled electronic devices.     Specification: Name:Mini 4 Channel USB Bluetooth Portable Mixer Live Studio Audio Mixing Console;  Material:Metal+plastic;  Input channel:4 channels;  Input:220V AC 50Hz;  Phantom supply voltage:+48V;  Consumed power:18 W;  Size(approx):23.5x20x3.5cm;  Maximum input level of microphone:+24dBu;  Maximum input level of line:+24dBu;  Maximum output level:+26dBu;  Main level meter:5 stage led;  Frequency response:20Hz-20kHz + 0.5dB;  Common mode rejection ratio (MIC 1kHz):> 75dB;  Total nil distortion (THD+N): 85dB;  Noise (22Hz to 22KHz):equivalent input noise -116dbu residual output noise < -80dbu;  Mono / stereo channel EQ: High frequency, broom type, +/-15db, 12KHz;  Low frequency, broom type, +/-15db, 80KHz;  High / medium frequency, peak valley type. +/-15db, 2.5KHz;  Fit for:applicable to the family KTV, campus speech, meeting etc.    Package included: 1x Mixing Console;  1x AC power Adapter;  1x User Manual;    Note: -Do not use this device near the TV, radio, stereo, cell phone or other electronic device, or it may cause noise.  -Please use a soft dry cloth for cleaning equipment  -Do not set any equalizer and level knob to the maximum position, otherwise it may cause acoustic feedback and damage the speaker