Yes - Cellular Innovations - 1 Channel Car Amplifiers

To power up your sub-woofers, install a mono amplifier. Among many features of a mono amplifier are low frequency reproduction, built in bass boost and low pass filters. A class D mono amplifier brings out less heat, are more efficient and draws less current.

One channel car amplifier provide users with a single audio input/output selector to power one speaker. This device is great if you only need to power a large woofer or subwoofer.