I was looking to find a simple answer to this issue, which seems to afflict
any usb sound device I use to connect to an analogue source. I did try the
internal card also, but that suffers from swooshes and other weird noises
due to it being inside a busy computer one assumes.
In the majority of cases the while is constant, though can vary if other
things are going on in the machine.
it seems to only be on the output sockets, and the input both line level
seem pretty good. This does not seem logical to me, but I've been told in
the main its because of the earth return through the usb and the one through
the mains are different impedances effectively modulating the supply. I did
find a special psu that supposedly fixes this sort off thing with a breaker
in the earth in the us be cable supplying isolated power only down the
line.
However most of these seem to be several times the cost of the interface.

I did wonder about a powered hub, but have been told this will not work.

Brian

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The Sofa of Brian Gaff...

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