sounds like rattly release bearing to me if it goes away when you put your foot on the clutch. when they get noisy they often sound like the bottom end is about to fall out when foot is off the peddle.
another thing is I've had quite a few exedy clutches play up recently where the dampening springs loose tension and rattle, and also another fault where the rivets holding the friction plate together back out and allow the middle spring part to rattle compared to the friction material on the outside. Very poor quality at the moment, bad few batches maybe as I've used exedy for years and been perfect but recently seem to have gone to shit.
Another one with the blitz active they do rattle like any single or twin plate clutch system that uses a floater plate under the pressure fingers. when you take the pressure away this floating plate rattles in its tolerance clearance. in this case that's totally normal, designed that way and not a problem or failure so mad_max926 don't worry on that.
Tim