The OC Bass from Whirlwind is a compact, pedal-style optical compressor and limiter specifically designed for use with your electric bass. The pedal can be switched between compressor and limiter modes. While both modes are designed to help your bass sound blend more evenly into the mix during live and studio performances, the limiter mode features a more aggressive gain reduction. The attack switch changes between three pre-defined attack rates, 'fast', 'medium' and 'slow.' This adjustable parameter can come in handy to make the attacks in your playing sound more pronounced. The pedal's input control adjusts the gain of the signal going into the compressor or limiter and, therefore, the amount of compression. The output knob adjusts the overall volume of the pedal.