The USB isolators block a potential path for a ground loop through the ground of the USB connector of the "computer" (Touch in this case). Whether this is necessary will of course depend on the computer and DAC and how the power supplies are hooked up. There has been so little use of USB DACs with the Touch that all the reports I know of are using the isolators with regular computers, so may or may not have relevance for the Touch.
The isolators themselves that I am aware of put the isolator in front of the USB receiver in the DAC, they all use the same chip. These chips DO add a significant amount of jitter to the USB signals themselves, whether this jitter winds up as jitter on the clock feeding the DAC chips (the only place where jitter really matters) is going to be VERY implementation dependant. In some DACs it won't get through to the clock, in others it will. So in some situations it comes down to a tradeoff between higher jitter and lower ground loop noise, or it may not do anything at all. Or it may make things worse! My personal favorite approach is to have a USB reciver running off the VBUS with the logic level outputs going through isolators (I prefer GMRs) to the rest of the DAC. This way everything having to do with the USB stays on the computer domain. John S. ------------------------------------------------------------------------ JohnSwenson's Profile: http://forums.slimdevices.com/member.php?userid=5974 View this thread: http://forums.slimdevices.com/showthread.php?t=94822 _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/mailman/listinfo/audiophiles
