QSC ISA 500Ti 260W 70V ISA Series Stereo Power Amplifier Designed as a cost-effective solution specifically for sound contractors, the ISA Series features seven models including four low impedance models (ISA 280, ISA 450, ISA 750, ISA 1350) rated for 2-ohm operation, and three "Ti" versions with isolated 25, 70 and 100 volt outputs for distributed audio systems (ISA 300Ti, ISA 500Ti, ISA 800Ti). Versatile loading options and a comprehensive feature set make the ISA Series a rugged, cost-effective power solution for any permanently installed sound system. Unique among distributed sound power amplifiers, the "Ti" versions will drive 8 or 4 ohm loads and a distributed system on the same channel simultaneously. This enables a contractor to reduce the number of required amplifier channels by allowing a limited number of distributed speakers to be attached to the same amp as is powering the main sound system. Housed in a rugged 3-U chassis, all seven models feature rear panel gain controls for tamper resistant operation with 2 dB detents for quick and repeatable settings. Inputs include both XLR and detachable Euro-style connectors. Outputs feature covered barrier strip connectors for safety agency compliance, and for added versatility, a DataPort V2 (Version 2) terminated with an HD-15 connector is provided for use with DPV2-compatible signal processing accessories such as the XC-3 Crossover, SF-3 Subwoofer Filter, LF-3 Low Frequency Filter and the DSP-3 with external power supply. Selectable high-pass filters are included to protect speakers and prevent speaker transformer saturation with minimal effect on program material. The ISA Series provide additional protection circuitry including DC, infrasonic, thermal overload, RF and short circuit protection. On the ISA 750 and ISA 800Ti, class H complementary bipolar output circuitry increases system efficiency by reducing AC power draw and waste heat by 40%. Cooling is accomplished via an automatic variable speed fan, which pulls air from back to front.