BBE Sonic Maximizer 422A for improved sound quality. By increasing harmonics, it sharpens the contours of musical instrument sounds. For vocals, the "s" and "sh" sounds become more prominent, making the lyrics easier to understand even if they overlap slightly with the backing music. The difference from the 462 model is that it has an auto mode. If there's a specific sound you want to emphasize, use manual mode; if there's no particular point to highlight, use auto mode and apply it subtly. There are some signs of wear and tear, such as dirt and scratches. Please take a close look at the photos. Some of the knobs are discolored. The functionality is not an issue. It has been checked. It has RCA and TS inputs and outputs. How about it for your home studio? No original box or instruction manual. The unit only. #BBE #Maximizer #Harmonics #Aphex #SonicMaximizer #SoundProcessor Thank you for looking.