The series of amplifiers are designed to work with a 100V line especially for sound systems installed in Office blocks, Shopping centers, Supermarkets, Bars, Public buildings, Airports, Metro/Railways, Auditoriums, Institutes etc. The main advantage of a 100V system is the reduced thickness of the speaker cables as compared to law voltage allows a much lower current flow for the same power. Another advantage of the high output voltage is the amplifier’s ability to cope up more easily with voltage drop when using long speaker cables. All HPA series amplifiers the output stage is powered by a low voltage allowing not only use with mains voltage but also 240VDC or (18VDC) voltage switching is automatic and completely silent. The output stage utilizes a specially wound transformer to allow full acoustic operation at high frequencies. A modified push-pull configuration is used for the output stage. This has the advantage of working a similar way to a bridge configuration allowing a decrease of the filtering volume by as much as a half. In contrast to contention push-pull configuration our output stage is fully complementary giving among-st other advantages lower distortion without losing advantages of a push-pull configuration. The output stage circuitry is protected with the same devices used in stage amplifiers. This includes Thermal protection, Input-output transformer protection, Short circuit, Overload protection, return limiter and soft switching (soft start). These features can be used in far more demanding conditions and gives greater fire safety protection. The HPA Amplifiers are equipped with priority inputs switched automatically as soon as additional signals are detected. The PVA series also has test inputs for connections. Balanced inputs allow the use of long cables without the risk of humming of main distortion. Subsonic filters protects the amplifier from saturation of the output transformer. The forced-cooling fan constantly adjusts its speed according to the temperature of the heat sink. The result of this is that when the amplifier operates at low volume the fan works at minimum speed or stops altogether minimizing dust intrusion and increasing the amplifier’s life.