I have previously asked for help with this problem, but my PSU died and I couldn't reply. See post viewtopic.php?f=3&t=4113&p=16346&hilit=rdac#p16346
I did do cesium's last request "Can you add "detect_trace=1" line to /usr/lib/oss/conf/osscore.conf and "usb_trace=3" to /usr/lib/oss/conf/oss_usb.conf? Then restart OSS. Maybe the output would be helpful..." but not sure where to look for the output.
I have got it going again and done some more tests, but am still not getting the USB DAC to work correctly. I have a Lynx AES16 which works perfectly and an ARCAM USB asynchronous rDAC. OS is vortexbox, v1.6 based on Fedora 14. I have tested with ALSA and the rDAC works perfectly, but the Lynx doesn't as they don't support it. With OSS I'm getting glitches of about 120ms where the output stops altogether, then restarts. I've verified this using ossplay to play a sinewave wav file and monitor the analogue outputs on a scope. Given it doesn't work with ossplay I'm confident it's a driver issue. The gaps mean it's unusable for music listening.
I would love to get both cards working in the same PC. I have requested help from opensound support over a week ago, but not got a reply. Any help would be much appreciated. soundon.log attached.