In further research it seems that with USB mics there seems to be some inheirent “noise” described as tape hiss like. Is this the case? I’m not looking for great studio quality sound (I’ll go to a real audio guy for that) but I would like as good quality as possible.
QT doesn’t play all codecs smoothly. Are your QT files exported using the DV50 codec? If so I would doubt that that would play back smoothly in the QT player. Also playing off the desktop probably is part of the problem; try putting the file on a faster drive.