Lightweight power amplifiers in a 19" rack-mountable housing for generating high sound pressure levels in medium to large sound reinforcement systems. H-series amplifiers employ a new hybrid class-H architecture, which combines the streamlined efficiency of a digitally controlled power section design with the power delivery and stability of a professional class-H output stage. Comprehensive internal protection monitors any thermal or overload conditions, automatically mutes at power on/off and provides active inrush limiting. A digital display continually shows the supply voltage, internal temperature and output level. A fully balanced signal path has 3 switchable input sensitivity levels to match different audio sources and the amplifier section can be set to operate in Stereo, Parallel or Bridge modes. A switchable 120Hz low-pass filter can be selected for use with subwoofers, avoiding the need for a separate crossover and saving additional expense and rack space. Speaker outputs can be connected using 1 or 2 Speakon leads as required. H-series amplifiers provide immediate and dynamic power on demand for sound contractors and PA installers that need dependable service with optimum sound quality.