Hello Jeremy,
I think I know what you are talking about! The GUI currently only offers Coax and Optical as options.
However, the Eval board can be forced into USB Audio mode by writing the following script.
Go up to View -> Command
Copy the following into the Window on the left and hit "execute"
# The following script is used for playback via USB
# RESET RESET THIS IS MASTER RESET FOR SRC (48kHz)
# Page 0 = DEFAULT for Control
# Write to page 0
#
w E0 7F 00
# Register 01, Bit 7 = 1 resets to default
d 100
w E0 01 80
# Delay 0.1 sec to allow part to reset
d 100
# Register 01, Bit 7 = 0 for normal operation
w E0 01 00
d 100
# w E0 7F 00
# Register 01, Bit 7 = 1 resets to default
#----- Setup Port A ------#
# 24bit I2S, Master mode, DIR source, at mute
# Divide by 256, MCLK input source
# Unmute Port A Output
# power on port A and B
w E0 01 38
# set up port A as master, 24 bit I2S sourced from port B
w E0 03 19
# select MCLK as source at 256fs
w E0 04 01
# port B slave, 24 bit I2S
w E0 05 01
#----- Setup DIR ------#
#DIR Config 1
# Input source: RX2 - S/PDIF RCA (default)
#w E0 0D 01
# Input source: RX4 - S/PDIF optical, RX_MUX = RX1
w E0 0D 08
#DIR Config 2 - default
w E0 0E 01
#----- Setup DIT -----#
# DIT COnfig 1
# Port A data in, DIv 256
w E0 07 80
# DIT Config 2
# Default is to output to RCA
# Commment out RCA and uncomment Optical for optical outputs
#Output to RCA
# TX - ON, TX MUTE - ON, Optical disabled
#w E0 08 06
# TX Mute - OFF
#w E0 08 04
#Output to Optical
# TX - OFF, TX MUTE - ON, optical disabled
w E0 08 03
# TX MUTE - OFF
w E0 08 01
#----- PLL Configuration -----#
# Set P=2, J=8, D=0
w E0 0F 22
w E0 10 1B
w E0 11 A3
# GPIO1 Config
# GPIO1 = RCVR non-audio data
w E0 1B 06
# GPIO2 Config
# GPIO2 = RCVR non-valid data
w E0 1C 07
# Power Status
# Disable RCVR (/PDRX) and Port B(/PDPB) power down and enable All Function power down
#w E0 01 14
#w E0 03 29