Taking a wild stab here ...
> A
> quick test of a clamp-on ferrite on the USB cable, then wrapping 10 or
> so turns of the cable around a bigger toroid did not make a dent in
> it.
Clamp-on ferrites affect common-mode noise only. If there is a switching
regulator that draws power off the USB lines while adding crap to it
(between power and gnd), it won't be affected by the filter because it isn't
common-mode.
My guess though is that the speaker leads might be the antenna.
Andy
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