Update:
Setting jack to playback only mode re-sets the sampling rate to 48000,
while duplex mode renders the following error message:
ALSA: cannot set period size to 128 frames for capture
ALSA: cannot configure capture channel
Complete output:
jackd 0.100.0
Copyright 2001-2005 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
JACK compiled with System V SHM support.
loading driver ..
apparent rate = 44100
creating alsa driver ...
plughw:0|plughw:0|128|2|44100|2|2|nomon|swmeter|-|32bit
control device hw:0
configuring for 44100Hz, period = 128 frames, buffer = 2 periods
ALSA: cannot set period size to 128 frames for capture
ALSA: cannot configure capture channel
cannot load driver module alsa
no message buffer overruns
Carlo