JACK non parte con zoom h4n come scheda audio esterna

[lopis]

ciao a tutti,
qualcuno mi può aiutare con il seguente problema:
uso jack con ardour (premetto che li trovo fantastici entrambi) e oggi ho provato per curiosità a collegare via usb il mio registratore portatile ZOOM h4n che è previsto possa essere usato anche come scheda audio. quando vado a cercarlo nel setup di jack lo trovo tranquillamente in hw:2 dove c'è scritto "h4". tuttavia quando lo seleziono e provo a far partire jack non parte.
nei messaggi esce questo:

21:58:02.988 Patchbay deactivated.
21:58:03.053 Statistics reset.
21:58:03.151 ALSA connection graph change.
21:58:03.624 ALSA connection change.
21:58:24.972 Startup script...
21:58:24.973 artsshell -q terminate
sh: artsshell: not found
21:58:25.374 Startup script terminated with exit status=32512.
21:58:25.374 JACK is starting...
21:58:25.375 /usr/bin/jackd -v -m -dalsa -dhw:2,0 -r44100 -p1024 -n2 -Xseq -H -M
jackd 0.118.0
Copyright 2001-2009 Paul Davis, Stephane Letz, Jack O'Quinn, Torben Hohn 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
Memory locking is unlimited - this is dangerous. You should probably alter the line:
    @audio  -  memlock    unlimited
in your /etc/limits.conf to read:
    @audio  -  memlock    1545291
21:58:25.415 JACK was started with PID=1859.
getting driver descriptor from /usr/lib/jack/jack_net.so
getting driver descriptor from /usr/lib/jack/jack_oss.so
getting driver descriptor from /usr/lib/jack/jack_dummy.so
getting driver descriptor from /usr/lib/jack/jack_alsa.so
getting driver descriptor from /usr/lib/jack/jack_firewire.so
no message buffer overruns
JACK compiled with System V SHM support.
server `default' registered
loading driver ..
apparent rate = 44100
creating alsa driver ... hw:2,0|hw:2,0|1024|2|44100|0|0|hwmon|hwmeter|-|32bit
control device hw:2
configuring for 44100Hz, period = 1024 frames (23.2 ms), buffer = 2 periods
ALSA: final selected sample format for capture: 16bit little-endian
ALSA: use 2 periods for capture
ALSA: final selected sample format for playback: 16bit little-endian
ALSA: use 2 periods for playback
registered builtin port type 32 bit float mono audio
registered builtin port type 8 bit raw midi
clock source = system clock via clock_gettime
new client: alsa_pcm, id = 1 type 1 @ 0x8fb2b68 fd = -1
start poll on 3 fd's
new buffer size 1024
registered port system:capture_1, offset = 4096
registered port system:capture_2, offset = 8192
registered port system:playback_1, offset = 0
registered port system:playback_2, offset = 0
++ jack_sort_graph
++ jack_rechain_graph():
+++ client is now alsa_pcm active ? 1
client alsa_pcm: internal client, execution_order=0.
-- jack_rechain_graph()
-- jack_sort_graph
ALSA: could not start playback (Broken pipe)
registered port alsa_pcm:Midi-Through/midi_capture_1, offset = 4096
registered port alsa_pcm:Midi-Through/midi_playback_1, offset = 0
registered port alsa_pcm:TiMidity/midi_playback_1, offset = 0
registered port alsa_pcm:TiMidity/midi_playback_2, offset = 0
registered port alsa_pcm:TiMidity/midi_playback_3, offset = 0
registered port alsa_pcm:TiMidity/midi_playback_4, offset = 0
DRIVER NT: could not start driver
cannot start driver
starting server engine shutdown
stopping driver
server thread back from poll
unloading driver
freeing shared port segments
stopping server thread
stopping watchdog thread
21:58:25.933 ALSA connection graph change.
last xrun delay: 0.000 usecs
max delay reported by backend: 0.000 usecs
freeing engine shared memory
max usecs: 0.000, engine deleted
cleaning up shared memory
cleaning up files
unregistering server `default'
21:58:26.000 JACK was stopped successfully.
21:58:26.001 Post-shutdown script...
21:58:26.001 killall jackd
jackd: nessun processo trovato
21:58:26.442 Post-shutdown script terminated with exit status=256.
21:58:27.675 Could not connect to JACK server as client. - Overall operation failed. - Unable to connect to server. Please check the messages window for more info.



quale è il problema?
per il settaggio di tutti gli altri parametri di jack uso la guida di droghetti che tutti conosciamo:
http://sites.google.com/site/stefanodro ... my-havings

Grazie