it happens randomly, while I play a soft synth, that jack XRUNs once, and the audio become crappy, noisy, like a kinda of digital effect....bit crusher? then all synthesizers (all audio apps) sound the same sh*t... i tried recording with ardour the output, and the output is clean, so I guess is a problem of sync or something that has to do with the hardware (soundcard). in order to record this noise, i had to connect the soundcard output in its input and record it via analog in: http://xaero.ath.cx/jackbug_stereo.wav.bz2 (it is a stereo file, with the clean track panned on the left, and the dirty one on the right). i hope it could be useful to debug the problem... what other information I can provide useful for debug? note that this happens with many version of alsa (1.0.9b, 1.0.10rc2, 1.0.7 or less) and with many kernels (gentoo-sources (slightly patched for speed improvement), ck-sources, ck-sources+realtime-lsm) i hope to solve this problem, since my audio desktop is unusable as si, since audio crasher after playng for just 5 minutes :(