Well, in Audacity, I can't play and record at the
same time, but I can
play a wav of the session in xmms while recording another track in
Audacity. Not sure if it's the SBLive or the app.
I've used an SBLive 512 with Audacity to do full duplex - but note that full
duplex in Audacity 1.0 for Linux doesn't work; a known bug. Try the latest
beta version 1.1.1 and see if full duplex works. That version has plenty of
bugs, but there is a new beta due next month.
What distribution are you using? There are some RPM's available.
Cheers
Daniel