This manual introduces the features of GZIA 1.600HPX-II, GZIA 2080HPX-II, GZIA 2130HPX-II, GZIA 2235HPX-II and GZIA 4115HPX-II, including power and protection indicators, bass booster, variable highpass, variable lowpass, auto-on @ High Level Input, adjustable input sensitivity, soft delayed remote turn-on, bass remote (1.600HPX-II, 2235HPX-II & GZIA 2130HPX-II optional) and thermal / short / overload protection.