For those asking, it is an HBE Retro, with three knobs, as noted, Sustain, Attack and Level. I raise Sustain to full level--it seems to make a positive difference, and is very much noticeable as sustain. I turn Attack all the way down, although at this point I am not quite sure why I did that. I think it added some noise. Level is just Level, and generally I try to match the output level on the compressor to whatever the normal output level is on the Cube amp. Thanks again.