Dell Speaker Buzz Question

I've got a new Dell A525, 30 watt 2.1 stereo speaker set with
the subwoofer.

When the speakers are on, at minimum volume, I hear a very low
level buzz coming out of the speakers.

The audio is fine when playing material. that's not the problem

That low level buzz is something that shouldn't be there.
Or at least I think it shouldn't be there.

Does anyone else have the same A525 speaker set up that I can
compare this to ?

FYI - the buzz is present irrespective of whether or not it's
plugged into the soundcard, irrespective of cable routing, and
completely independent of AC outlets that it's plugged into.

So conductive EMI from external sources does not appear to be
the cause.

My old Altec Lansing speakers (w/sub woofer too), are completely
silent when no audio is being fed to them.

My thinking is I have a bad speaker with AC filtering hosed up
on it's internal power supply.

That's why I'm asking if anyone else has the same speaker that I
can compare notes with (before I call Dell and request a new
warranty replacement).

It's a very low level buzz & in a quiet room, when your ears
are near the speakers, you can hear it.