Working USB sound card?

[Thomas Orgis]

Am Thu, 10 Mar 2011 10:44:49 +0100
schrieb Giuliano Braglia <forevergyl at gmail.com>: 

> I will receive the alesis io2 express next week :)
> 
> can anyone tell me if I have to do something particular in order to install
> it?

You simply plug in the USB wire (yay for bus power), the "USB" LED should light up on the device and the kernel should give a brief note in dmesg:

shell$ dmesg
usb 3-1: new full speed USB device using uhci_hcd and address 2
2:1:1: cannot get freq at ep 0x1
usbcore: registered new interface driver snd-usb-audio

Then, you should have plain ALSA devices, for audio:

shell$ LANG=C aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: Intel [HDA Intel], device 0: CONEXANT Analog [CONEXANT Analog]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: Intel [HDA Intel], device 1: Conexant Digital [Conexant Digital]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: io2 [io|2], device 0: USB Audio [USB Audio]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

... and for MIDI (I had to load the snd-seq module on a custom install, I doubt you'll have to do that):

shell$ LANG=C aconnect -o
client 14: 'Midi Through' [type=kernel]
    0 'Midi Through Port-0'
client 20: 'io|2' [type=kernel]
    0 'io|2 MIDI 1     '
shell$ LANG=C aconnect -i
client 0: 'System' [type=kernel]
    0 'Timer           '
    1 'Announce        '
client 14: 'Midi Through' [type=kernel]
    0 'Midi Through Port-0'
client 20: 'io|2' [type=kernel]
    0 'io|2 MIDI 1     '


Select the respective ALSA device for JACK to use and you're set. Of course you can just use it with ALSA applications, too. Only restriction is, when you use the hw device directly, your app must support 24 bit sample format (really s24_3, as that is what makes it possible to shift 24bit/48kHz through USB 1 reliably). But the default plughw does the necessary conversion for you.

I'll quickly test MIDI with hydrogen... using the swissonic USB MIDI thingie as thru cable ... yes, I can record and play MIDI from/to my Roland drum computer. No idea about jitter, but basic functionality is there.

Really, I'm extremely happy with this box ... no issues, especially compared to the hair-pulling I had over getting a system that plays nicely with the firewire setup (but then, I don't have 8 analog channels on the io|2).


Alrighty then,

Thomas.
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