I have successfully recorded from my
USBDualTubePre microphone preamp using the S/PDIF
into my M-Audio 2496. I used mhWaveEdit.
The issue was that qjackctl was displaying the
Readable Clients/Output Ports and
Writable Clients/Input Ports of my _motherboard_
audio, not my M-Audio 2496.
A recent off list reply coached me to set the
correct device in Qjackctl with "Setup | Interface | >".
Early on, Len Ovens informed me that the S/PDIF
inputs of the ice1712 are 9 and 10.
And of course, using envy24control to set "Master clock"
to s/pdif rather than a sample rate was required as well.
And so, thank you to all who responded!