Product Details  89db  With MP3 and USB interface sd/usb audio Karaoke colourful digital display screen(different with SA-21)89db Impedance:4Ω-8Ω Frequency response:40Hz-18HKz 2.1 multimedia audio PANEL OPERATION EXPLAINATION  POWER--Power supplys witch VOLUME--General volume adjust BASS--Bass adjust TREBLE--Treble adjust MIC.VOL--Mic volume adjust ECHO--Echo time adjust TONE--Tone adjust SUB VOL--Bass volumn eadjusst BACK PANEL CONNECTION Power supply plug Left/right voice-box output Left/right voice resource input IPPORTANT SAFETY METHODS 1,Power wire protection: pay attention not to step or put heavy object on power wire,specially take care of power wire plug, outlet socker of unit dont lengthen wire of make all power supply socket over loaded,because this can cause fire or ellectricity shock,dont pull ,drug power wire. 2,Aeration: the unit mast be put in places where aeration is good, in order to keep aeration good dont put dist or covertable-cloth on it. the distance between the unit and the wall mustnt less than 10cm dont put it on bed,sofa, carprt,or similar object surface to avoid shocking intake. 3.Unit shell remove wire avoid removing unit shell.if you touch inner components,severe risk of electricity-shock may happen. 4.Exceptional smell if you find exceptional smell and smoke,you should immediately cut power supply and remove plug from socket,and connect with sell shop or nearest maintain center. 4.At tention: the unit uses AC240V+50Hz-60Hz power supply,dontuse nonstandard power supply and low-power adjust stable-power supply.