Since on the Mac I'm still seeing the signal both limited in range and overloaded (still all that clipping) I think it's clear the issue lies either in the cable or the Blue Yeti itself. You were ahead of me in thinking (correctly) about hardware. Sad, but at least I can rule out Skype or other applications on my machine, or any Windows system issue. When taking the mic to a different machine however (a Mac) I got some real results: same wonky signal. While Skype is clearly happy to hijack the Windows mic level control, I think I successfully took Skype out of the equation and saw no change. I also had gone through the steps you recommended for Skype - doing everything to make sure it was truly shut down (closing, checking for persisting processes, restarting) to no avail.
Thanks for all the advice - I think you're on to it.
