thank-you all for your advices!
even if i start jack as non-root user without the realtime option the
program tell me "could not connect to jack server as client".
this is the message board
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20:06:02.725 Patchbay deactivated.
20:06:02.838 Statistics reset.
20:06:02.851 JACK is starting...
20:06:02.851 /usr/bin/jackd -m -dalsa -r44100 -p512 -n2 -D -C/dev/dsp
-P/dev/dsp -i2 -o2
20:06:02.996 JACK was started with PID=12301 (0x300d).
jackd 0.99.0
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 ..
apparent rate = 44100
creating alsa driver ... /dev/dsp|/dev/dsp|512|2|44100|2|2|nomon|
swmeter|-|32bit
ALSA lib pcm.c:2084:(snd_pcm_open_noupdate) Unknown PCM /dev/dsp
ALSA lib pcm.c:2084:(snd_pcm_open_noupdate) Unknown PCM /dev/dsp
ALSA: Cannot open PCM device alsa_pcm for playback. Falling back to
capture-only mode
cannot load driver module alsa
20:06:03.116 JACK was stopped successfully.
20:06:03.121 MIDI connection graph change.
20:06:03.199 MIDI connection change.
20:06:05.211 Could not connect to JACK server as client.
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thanx,
emanuele