snd-usb-hiface config 0 descriptor??

I'm testing a USB DAC that seems to work fine except it does not
produce sound.  The only clue I can find is "config 0 descriptor??" in
dmesg below.  This DAC needs to be unmuted before it will work but
alsamixer says "This sound device does not have any controls."

# dmesg
...
usb 1-2: new high-speed USB device number 14 using xhci_hcd
usb 1-2: device descriptor read/64, error -71
usb 1-2: New USB device found, idVendor=249c, idProduct=9006, bcdDevice= 0.01
usb 1-2: New USB device strings: Mfr=1, Product=2, SerialNumber=0
usb 1-2: Product: Computer Audio Design
usb 1-2: Manufacturer: Computer Audio Design
usb 1-2: config 0 descriptor??

# lsusb
...
Bus 001 Device 012: ID 249c:9006 M2Tech s.r.l. Computer Audio Design
...

# cat /proc/asound/cards
...
1 [CAD ]: snd-usb-hiface - CAD
CAD at usb-0000:00:14.0-2

Any ideas?