The Pioneer SX-990 is a stereo receiver that was produced in the late 1970s. It features a power output of approximately 50 watts per channel and offers AM/FM radio tuning capabilities. The SX-990 has various inputs for connecting multiple audio sources, including phono and auxiliary inputs. It also comes with a built-in equalizer, providing users the ability to adjust sound frequency to their preferences. The unit is characterized by its classic design, featuring silver front panels, rotary knobs, and analog tuning meters.