I don't know if you ever found a solution to this problem but, I did find this in a Sound On Sound review of the Voice Channel, while doing research on the unit.
"That the USB socket offers a way to get audio directly into your computer
system without a separate interface is beyond doubt. However, ART provide no dedicated low-latency driver, and because the Voice Channel has no playback monitoring facilities of its own,
Windows users may need to download a third-party multi-device audio driver to record via the Voice Channel and listen back at the same time.
Mac users can rely on Core Audio to co-ordinate the Voice Channel with any other audio hardware on their system, and while Core Audio apparently provides pretty good latency
performance in general, latency proved to be a problem on my PC system. In
Reaper, which supports multi-device operation using the plug-and-play windows drivers, the latency delay was large enough to feel like a permanent slapback echo, while in Cubase, under Michael Tippach’s freeware universal multi-device driver, ASIO4ALL, I still couldn’t get the latency any lower than 27ms. Even at this kind of latency, software monitoring choruses obviously with direct spill, and timing feels distinctly sluggish. In short: don’t expect to use software monitoring with the Voice Channel unless you’ve checked that the latency is acceptable on your system."
I don't know if that helps you or not but, I just read that last night and came across this thread in tonight's research.
