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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