DESC: The new Reference series amplifiers build upon Infinity's reputation for performance and design that's been leading the industry for almost 40 years. Reference series subwoofer amplifiers utilize high-frequency Class D switching technology, which is far more efficient than traditional Class A/B power amplifiers. Class D circuitry allows for voltage switching, which manages the power output to ensure peak performance with minimum drain on your vehicle's charging system. The Reference series 611a is a high-performance, single-channel amplifier capable of pushing over 600 watts of crystal clear sound. Infinity's proprietary Dynamic Bass Optimizer (DBO) circuit matches variable bass boost with a variable subsonic filter to enable low frequency fine-tuning while still providing robust speaker protection. Other features include two sets of parallel output terminals for easy connection of multiple woofers, and an optional remote level control.