This series is noise-free,the circuit type is classAB.ClassAB can make less destortion and better sound.Integrate protect,DC output protect funtion,longtiome over-heat protect funtion,turn on delay funtion.It can speedy protect the circuit when the amp short circuit and over loading. The unit has various input/output connectors,it have 3 way senditivity switch for choose level,stereo,bridger-mono,parallel mono.