The SRM-252S is an exclusive driver unit (amplifier) for driving STAX ear speakers with PRO-bias 5 pins. Its line input can directly connect to the audio output terminal of CD player, portable audio player and PC. The SRM-252S has a simple design that excels in sound quality employing the carefully selected newest high-voltage transistors and low-noise FETs. The output stage featuring the emitter-follower configuration reinforces the driving performance and also realized the smooth sound quality. Moreover, the class-A amplification throughout the stages with no coupling capacitors reproduces exhaustively the finest nuance of music. Although the SRM-252S includes a class-A DC amplifier in a compact CD jacket size case, the internal heat is effectively dissipated through the chassis of aluminum extrusion material to improve the reliability over a long period of time. Also, the parallel output terminal was added to distribute the source signal so that a loud speaker may also be simultaneously used when source equipment has only a pair of output terminals.