Quad Electroacoustics Limited

909 Stereo 2 channel current dumping amplifier Introduction The 909 Stereo power amplifier incorporates Quads patented current dumping technology and is one of the finest audio amplifiers available today. The current dumping technique eliminates many of the problems associated with transistor amplifiers giving a consistent and predictable performance without a need for the fine tuning adjustments on the production line. In current dumping amplifiers there is a very high quality low power output amplifier and a very high power output amplifier whose performance is not critical. This high power output amplifier controls the loudspeaker at all times and provides the current or muscle to generate the sound. The low power output amplifier is arranged to generate a signal that compensates for errors between the input signal and the signal fed to the loudspeakers. The result is that the quality and accuracy of the output signal depends only upon the performance of the low power amplifier. In the 909 this low power output amplifier has been engineered to the highest standards. The problems of crossover distortion; quiescent current adjustment; thermal tracking and transistor matching all disappear. If such a thing as a perfect amplifier were to exist, then the 909 would be very close to that perfection.