The T.Rex Comp Nova is a very transparent compressor. It has a clean, natural sound, with minimal coloration. There is no loss of low end, no humps or scoops in the mids, and the highs roll off in a mild slope. The noise floor is fairly low, unless you crank the compression all the way up.
 
Knobs include Comp, Level (output volume) and Attack. The Attack knob has a wide time range, but most of that range is very slow, so any subtle adjustment of your initial note attack will have to be done near the fastest end of the knob turn. Between the slow attack and the nature of this type of comp circuit where your signal gets squeezed progressively stronger, it is no good as a hard peak limiter. But it excels at adding smoothness, some fatness, and sustain. You'll get the best results with the Comp knob near noon, depending on the output level of your instrument.