I've looked for a Fine Manual on this but no luck: Jack starts OK with a period size of 512 but with 256 or 128 it seems to say that the ALSA driver refuses to accept it. Does anyone know, is this a hardware limitation of the card, or something I can change with a magic parameter in some configuration file? The card is an old SBLive Value (the box said something about MP3) and the software is Red Hat 8 / Planet CCRMA / emu10k1. If I have understood the Jack documentation correctly, this corresponds to about a 35 millisecond buffering delay for the round trip of a signal from the outside world into the computer and back out again. Plus any time spent processing the signal inside the computer. Not bad, really, I guess. I wonder what an M-Audio Delta could do? jackstart -R -d alsa -d hw:0 -p 256 -n 2 -r 44100 jackd 0.67.2 Copyright 2001-2003 Paul Davis and others. jackd comes with ABSOLUTELY NO WARRANTY This is free software, and you are welcome to redistribute it under certain conditions; see the file COPYING for details loading driver .. driver client name = [alsa_pcm] creating alsa driver ... hw:0|256|2|44100|swmon|swmeter|rt open ALSA: cannot set period size to 256 frames for capture ALSA: cannot configure capture channel starting engine engine driver not set; cannot start cannot start main JACK thread jack main caught signal 15 -- sigmotto: Liberty is theft.