Hi Paul and All, Unfortunately this device is Big Endian so I need to use plughw also using a play: $ aplay -D plughw:2 /usr/share/sounds/shutdown1.wav -v Playing WAVE '/usr/share/sounds/shutdown1.wav' : Signed 16 bit Little Endian, Rate 44100 Hz, Stereo Plug PCM: Linear conversion PCM (S16_BE) Its setup is: stream : PLAYBACK access : RW_INTERLEAVED format : S16_LE subformat : STD channels : 2 rate : 44100 exact rate : 44100 (44100/1) msbits : 16 buffer_size : 16384 period_size : 4096 period_time : 92879 tick_time : 1000 tstamp_mode : NONE period_step : 1 sleep_min : 0 avail_min : 4096 xfer_align : 4096 start_threshold : 16384 stop_threshold : 16384 silence_threshold: 0 silence_size : 0 boundary : 1073741824 Slave: Hardware PCM card 2 'Audiophile USB (tm)' device 0 subdevice 0 Its setup is: stream : PLAYBACK access : MMAP_INTERLEAVED format : S16_BE subformat : STD channels : 2 rate : 44100 exact rate : 44100 (44100/1) msbits : 16 buffer_size : 16384 period_size : 4096 period_time : 92879 tick_time : 1000 tstamp_mode : NONE period_step : 1 sleep_min : 0 avail_min : 4096 xfer_align : 4096 start_threshold : 16384 stop_threshold : 16384 silence_threshold: 0 silence_size : 0 boundary : 1073741824 You're right, I'll try to start with a better setup using the parameters above, first block, and using plughw because BE, jackd -v -dalsa -dplughw:2 -r44100 -p4096 -n4 -S the problem is that I get the card playing few milliseconds of audio continuously even without using any player connected to Jack. A sort of tic -tac - tic -tac .... if I reduce p to 1024 then it seems to work fine but the quality is still lousy. See below part of the output, any suggestion is most welcome. $ jackd -v -dalsa -dplughw:2 -r44100 -p4096 -n4 -S 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_oss.so jackd 0.100.1 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. server `default' registered loading driver .. apparent rate = 44100 creating alsa driver ... plughw:2|plughw:2|4096|4|44100|0|0|nomon| swmeter|-|16bit control device hw:2 configuring for 44100Hz, period = 4096 frames, buffer = 4 periods You appear to be using the ALSA software "plug" layer, probably a result of using the "default" ALSA device. This is less efficient than it could be. Consider using a hardware device instead rather than using the plug layer. Usually the name of the hardware device that corresponds to the first soun nperiods = 4 for capture registered builtin port type 32 bit float mono audio new client: alsa_pcm, id = 1 type 1 @ 0x8746a78 fd = -1 You appear to be using the ALSA software "plug" layer, probably a result of using the "default" ALSA device. This is less efficient than it could be. Consider using a hardware device instead rather than using the plug layer. Usually the name of the hardware device that corresponds to the first soun nperiods = 4 for playback new buffer size 4096 registered port alsa_pcm:capture_1, offset = 16384 registered port alsa_pcm:capture_2, offset = 32768 registered port alsa_pcm:playback_1, offset = 0 registered port alsa_pcm:playback_2, offset = 0 ++ jack_rechain_graph(): client alsa_pcm: internal client, execution_order=0. -- jack_rechain_graph() 4167 waiting for signals late driver wakeup: nframes to process = 8192. load = 0.2853 max usecs: 530.000, spare = 92349.000 ..... Thank You in advance Ronny