The USB input to the AP, even the PP version, uses the 5V power line, so it wouldn't work. The PP only supplies the internal clock. See the diagram picture on the PP site: http://www.audiophilleo.com/ppgallery.aspx
Thanks for this info. So there is probably even more scope for cleaning signal AND power before it gets to the AP. Could it improve it I wonder?
I doubt it. A few of us have tried using better power through USB with no noticeable differences. That only seems to work with the standard AP1/2 (without the Pure Power).