28 May
2010
28 May
'10
8:40 p.m.
On Fri, 28 May 2010, Folderol wrote:
Once you connect the analogue side of the the USB device to the
installed (high quality card) you have an earth loop that traverses
both the analogue and digital domains. You also have an +5V loop (unless
the USB device is externally powered) This loop does not exist when the
USB card is self testing. I still can't think exactly how, but I
believe this is likely to be a significant part of the problem.
OK... but ground loops usually produce noise or a DC offset,
right? What could be causing the ground loop to oscillate?
-gabriel