Here's what Ashdown say about the Velvet Compressor:
A principal use of any good compressor is an effect to smooth out and level the dynamic range from the instrument. Whilst most modern bass amplifiers are equipped with a much-simplified version of this type, some lack this key feature.
Designed to make your bass sound silky smooth, The Ashdown Velvet Compressor is a stunning, well-rounded compressor pedal.
The Velvet Compressor is a simple pedal with advanced circuitry. Just one knob adjusts several parameters simultaneously – Gain, Ratio and Threshold are all synchronised and adjusted with the “Compact” knob whilst Attack and Decay are optimised and pre-set to suit the signal passing through.
In use, the Velvet Compressor should be set so that the volume does not change when the pedal is switched on/off. This is achieved by adjusting the “Input” and ‘Output” level controls. The “Input” rotary control has an accompanying 3-band (white blue and red) LED light control to assist you in setting the perfect input level before hitting the compressor.
The light tickling the blue being the recommended amount. With your input signal at its optimum, set the overall output of the pedal into the amplifier with the “Output” control.