How to disable HDMI audio and use USB device on BBB?

[JimS]

I have followed the instructions here (skipped the alsa stuff as it appeared to already be in place).
http://andicelabs.com/2014/03/usb-audio-beaglebone/

The HDMI device still appears when I do:
aplay -l
and I can't seem to get any commands to use the USB device to run without errors. Have tried aplay, play and sox.
Just trying to play short wav files to indicate some event is happening.

Here is output:
root@raspbx:~# aplay -l
* List of PLAYBACK Hardware Devices *
card 0: Black [TI BeagleBone Black], device 0: HDMI hdmi-hifi-0 []
Subdevices: 1/1
Subdevice #0: subdevice #0
card 1: Device [C-Media USB Audio Device], device 0: USB Audio [USB Audio]
Subdevices: 1/1
Subdevice #0: subdevice #0
root@raspbx:~#

What should I be doing/looking at?

[JimS]

aplay results in two underrun messages and then locks up. The LEDs freeze like described here:
https://groups.google.com/forum/#!topic/beagleboard/fYiYCdq-6ik
and I have to power cycle to recover. I am lost on what that thread discusses for addressing the issue.
I thought it might be a power problem so I added a powered hub for the audio device with no change.
Help please...