Thanks for the suggestions so far. I haven't been able to figure out how to play through the Speedio without running Jack. Running in XMMS (the GUI part), I can select the ALSA driver as the output plugin, then select "Speedio: USB Audio (hw:1,0)" for output. But when I hit play, I get an error: "Failed to open audio output". In fact, I get this error with any ALSA output choice except "default PCM output" (which plays fine through my regular soundcard). I turned next to aplay. This is the output of aplay -l: **** List of PLAYBACK Hardware Devices **** card 0: CMI8738MC6 [C-Media PCI CMI8738-MC6], device 0: CMI8738-MC6 [C-Media PCI DAC/ADC] Subdevices: 1/1 Subdevice #0: subdevice #0 card 0: CMI8738MC6 [C-Media PCI CMI8738-MC6], device 1: CMI8738-MC6 [C-Media PCI 2nd DAC] Subdevices: 1/1 Subdevice #0: subdevice #0 card 0: CMI8738MC6 [C-Media PCI CMI8738-MC6], device 2: CMI8738-MC6 [C-Media PCI IEC958] Subdevices: 1/1 Subdevice #0: subdevice #0 card 1: Speedio [Speedio], device 0: USB Audio [USB Audio] Subdevices: 0/1 Subdevice #0: subdevice #0 If I run aplay somefile.wav, with no other parameters, it plays fine through the regular soundcard. But if I try aplay -Dhw:1,0 somefile.wav, I get an error: "Sample format non [sic] available". I tried -f cd and all available 24 bit formats with the -f switch (since Jack thinks the Speedio is a 24 bit device) but none worked. The output of /proc/asound/card1/stream0 is: Novation EMS Speedio at usb-0000:00:03.1-2, full speed : USB Audio Playback: Status: Stop Interface 1 Altset 1 Format: S24_3LE Channels: 2 Endpoint: 1 OUT (ADAPTIVE) Rates: 44100, 48000 Capture: Status: Stop Interface 2 Altset 1 Format: S24_3LE Channels: 2 Endpoint: 2 IN (SYNC) Rates: 44100, 48000 I guess that's telling me the correct format to use with aplay is S24_3LE, so I tried this again. It gave me the message "Warning: format is changed to S16_LE" and then, as before, "Sample format non available". Sorry if these are elementary misunderstandings on my part - this is all a bit new to me. Any more ideas of things to try? Regards, Peter C