> iirc, you should use the same user to start jackd and Pd.
> so if you run Pd as user "chi", than you should also run jackd as user
>"chi". the same if you use root (which i don't recommend; you should
>rather fix your /etc/security/limits.conf to be able to run realtime
>processes as member of the audio-group).

Thanks..

I've resolved the problem of "user" adding (as root) those rows in /etc/security/limits.conf:

@audio - rtprio 80
@audio - memlock 288000
#288000 because my RAM is 576 MB
@audio - nice -10

and I set user in "audio" member group.
_______________________
In JACK setup I set: 
realtime, priority 80
midi driver: seq
_______________________
So now I can open qjackctl and start JACK correctly (play), but give me this error:

cannot use real-time scheduling (FIFO at priority 90) [for thread -1238557840, from 
thread -1238557840] (1: Operation not permitted)


Now I open pd, and in "media" I select: JACK, and ALSA-MIDI. 

Then I open JACK connections: I see 2 windows: AUDIO and MIDI. Here, in both windows,  I connect pd with 
my SB LIVE! sound card.
____________________________________________
Now, running some patch in pd, happen this:

1)in a audio patch (for example a simple oscillator with a slide..) *I can listen sound correctly* (even if 
with a fastidious background noise) and I can change frequency well with the slide.

2)in a midi patch (a patch certainly correct, tested in o.s. Windows..!) *I can't listen anything*. 
I see numbers change, but *no sound*.

PD give me this error:

audio I/O error history:
seconds ago	error type
     1.39	A/D/A sync
     3.25	A/D/A sync
     3.28	A/D/A sync
     3.37	A/D/A sync
     3.38	A/D/A sync
   (..etc..etc..similarly)


Thank you in advance,
cb