are you getting noise from all outputs(mains, headphones, 8outs if you have it) on your machine or just when recording to the computer? what it seems like is just static electronic noise.. do you use a power conditioner or do you have a ton of plugs in one socket or utility power strip? also it can come from a really high gain and a low input level i.e the gain is picking up noise for the lack of volume being input like whispering in a mic with the gain all the way up its still quiet but if you were to normalize, the white noise would become more than evident..
if it sounds like spectral phasing or popping and hissing it could be your outputs or type of connection i had a friend who left his machine on all the time cuz he couldnt save and his machine overheated several times and developed weird habits that varied and even popped sometimes only when he changed pad banks it was really unexplainable but most likely has to do with your recording process...
