The Hitachi HMA-9500 is a stereo power amplifier that made its debut in 1977. This model is notable for being one of the first to utilize power MOS FETs as amplifying elements in its power stage. The use of power MOS FETs allows for a higher amplification factor and excellent linearity compared to traditional small-signal MOS FETs, as well as superior high-frequency characteristics that outperform bipolar transistors. The design features a pure complimentary service OCL circuit with a two-stage differential amplifier configuration, which ensures reduced distortion and improved sound quality. With its innovative design, the HMA-9500 is capable of delivering effective output of 100W + 100W at 8 ohms from 5 Hz to 100 kHz, and 120W + 120W from 5 Hz to 20 kHz. The total harmonic distortion is impressively low, at 0.01% for rated output at 8 ohms across a broad frequency range. Notably, the amplifier has a DC configuration without any capacitors in the NFB loop to eliminate components that could detract from sound quality. The HMA-9500 is designed with symmetrical, separated input and output to minimize channel interference, and includes gold-plated input pin jacks for enhanced connectivity. Moreover, the amplifier features a robust damping factor of 70 and is optimized for load impedances ranging from 4 ohms to 16 ohms. With a weight of 28 kg and dimensions of 435 mm in width, 192 mm in height, and 410 mm in depth, this unit combines performance with a substantial build.
