Update (from the manual):
Helix functions as a USB 2.0, multiple-input/output, 24-bit - 96kHz, low-latency audio
interface for Windows® and Mac® computers, as well as for iPad and iPhone (with
optional Apple Camera Connection Kit adapter), and is compatible with all major DAW
software.
NOTE: For USB audio operation on Windows® computers, it is necessary to
download and install the Line 6 Helix ASIO® driver (see page 56). For Mac®
computers, it is only necessary to download and install the Line 6 Mac® Core
Audio driver if you desire audio sample rate operation at rates other than 48kHz
(see page 56). These drivers are available from line6.com/software. There is no
driver installation necessary for an Apple iPad or iPhone.
This seems to imply the USB is set to 48kHz as standard and can be changed thrue the driver software.
Don't ypu just love manuals?