On Fri, 28 May 2010, Veronica Merryfield wrote:
The 100 Hz (being 2x 50Hz, the power freq. in
Italy)
suggests that it is probably related to some manner of
power supply. However, I have no theory why we're
getting 2x 50Hz (and I think I need one :-)).
The implication has been that the USB audio device is a
cheaper device. It is therefore more likely that the
device runs from the USB 5 volt line than have a separate
power supply, and that 5v line is regulated and therefore
less likely to have a power line ripple on it.
Yes, as I go back and read that A was proven by A... it
could be the power source for either device -- and most
likely the "cheaper" card A.
-gabriel