The PDA Series amplifiers have a great design that eliminates the need of an subwoofer amplifier with its powerfull 3rd channel.Designed specifically to meet the demands of heavy-duty live sound reinforcement touring systems and large-scale installations, the Sti Audio PDA-Series power amplifiers uses a proven Class-D topology to deliver reliable, high headroom output power. Engineered with a low noise signal path and a high current, reduced stray magnetic field toroidal transformer to reduce potential hum and noise, the multi -tier power conversion design delivers superior transient response and low measured distortion - equal to the best of analog amplifier design. An impedance aware design deals with the realities of driving typical reactive speaker loads and addresses the associated problems such as thermal shutdown, inductive snap-back, and premature current limiting. PDA Series amplifiers will easily drive reactive phase shifted loads while remaining fully protected against accidental short circuits. An advanced protection scheme ensures the loudspeaker won't experience harmful DC offset voltages while protecting the amplifier from abnormal load, AC power brownout, and high temperature failures. A user-defeat able transparent peak limiter lowers distortion at high power operating conditions, and provides ample protection for the loudspeaker's components. A 'soft turn-on' circuit eliminates transient damage to connected loudspeaker systems and prevents nuisance circuit breaker-tripping during the amplifier's power up procedure. The computer-optimized fan front-to- rear cooling system incorporates ultra-quiet, variable-speed internal fans ensuring that the output power transistors operate with ample thermal margin. Front panel Power, Protect, Activity and Clip LED's are bright and easy to see and all knobs are recessed for safe, easy transportation.