No audio

Hello,
I decided to give Qtractor a go as it seems really cool.
The thing is that I'm having some problems with audio output , I can' hear anything (just imported a midi track)
I m having the same problem with Muse so it would be nice if you can help me solving the issue
I m on Ubuntu 14.04

these are the messages

12:40:03.217 Session closed.
12:40:04.249 Session started.
12:40:04.249 New session: "Untitled1".
Cannot connect to server socket err = No such file or directory
Cannot connect to server request channel
Cannot connect to server socket err = No such file or directory
Cannot connect to server request channel
Cannot create thread 1 Operation not permitted
Cannot create thread 1 Operation not permitted
Cannot create thread 1 Operation not permitted
jackdmp 1.9.10
Copyright 2001-2005 Paul Davis and others.
Copyright 2004-2013 Grame.
jackdmp 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 server starting in realtime mode with priority 10
Cannot lock down 82274202 byte memory area (Cannot allocate memory)
audio_reservation_init
Acquire audio card Audio0
creating alsa driver ... hw:0|hw:0|1024|2|48000|0|0|nomon|swmeter|-|32bit
configuring for 48000Hz, period = 1024 frames (21.3 ms), buffer = 2 periods
ALSA: final selected sample format for capture: 32bit integer little-endian

ALSA: use 2 periods for capture
ALSA: final selected sample format for playback: 32bit integer little-endian
ALSA: use 2 periods for playback
Cannot use real-time scheduling (RR/10)(1: Operation not permitted)
AcquireSelfRealTime error
Cannot lock down 82274202 byte memory area (Cannot allocate memory)
Cannot use real-time scheduling (RR/5)(1: Operation not permitted)
JackClient::AcquireSelfRealTime error

12:40:04.820 Audio connections change.
12:40:04.822 MIDI connections change.

thanks !