In article , Don Pearce
wrote:
On Sun, 12 Feb 2017 20:50:07 -0000, "Brian Gaff"
wrote:

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

I've never come across this problem. Can you give more detail about your
system?

IIRC Brian is using one of the cheap USB Audio devices that tend to pick up
any crap on their USB power line, etc.

No idea who told him an externally powered hub "will not work". I found
that a decent one could make a difference when using a 25 quid USB DAC/ADC.
As does buying a better ADC or DAC in the first place!

Jim

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