The Marantz SM-500 DC is a power amplifier that was introduced in the mid-1970s. It is a high-performance amplifier designed to deliver clean, powerful audio output with low distortion. The unit features a robust design with a high output power rating, making it suitable for driving a variety of speakers. Its design often incorporates discrete transistor output stages and a transformer-based power supply to enhance audio fidelity. The SM-500 DC is known for its reliability and build quality, making it a sought-after model among audiophiles who appreciate vintage audio equipment.