Audio, hi-fi and car audio - The whine of usb audio interfaces

Well lett me add some detail. The whine actually drops to almost nothing at
all when software is loading. It is more or less constant when nothing much
other than listening to internet radio is going on, and this includes
actually recording audio.
The audio if moved to a ram stick then played in an mp3 player has no
whine, only the sound through the phonos on the sound interface have it.
My feeling is that its something to do with the samsung solid state drive
in the computer, as at our talking newspaper a similar machine is there
with a conventional hard drive and it gives no whine at all, but does suffer
from the sort of crackle one might expect to hear on the mains, for example
again only on the output.
The isolated power devices seem to cost anything from nearly 50 quid up as
high as your budget will go, no doubt with oxygen free cables and gold
plated everything supplied by russ Andrews.

However if the sound is just coming up the psu line surely any decent
powered usb hum should fix it assuming the 5v supply its derived from is not
one of those really crude Chinese devices that generates rfi on all bands
and no doubt nasty noises on the output as well. This is why I was looking
for something analogue and perhaps with simple voltage regulation and
smoothing not switch mode.
Brian

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This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
"Jim Lesurf" wrote in message
...
In article , Arthur Quinn
wrote:

When I had this problem some while ago between an iMac and a fixed HiFi
system using an M-Audio DAC, I guessed that it was an earth loop
problem and tried transformer coupling the audio. That cured it.

I believe that this whine is a quite common problem and there are
readily available USB isolators that will break the earth connection on
the USB lead.

The difficulty here is that there are actually various causes and ways the
symptoms can manifest, and they have different solutions and mechanisms.
Knowing *exactly* what is meant by "whine", and the relevant circumstances
may help diagnosis. Note, for example, the oddity in what Brian said
initially:

On 12 Feb in uk.rec.audio, Brian Gaff wrote:
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.

Jim

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