I've just bought an ARCAM rPAC external USB sound device, and after a lot of hours spent, I just can't get it to work on Ubuntu 12.04 64bit setup.

It uses a TI PCM5102 DAC chipset with Asynchronous USB. I don't think there's a need for a special driver for it, as the rPAC works fine on Windows/Mac OS X using the generic USB driver.

When I plug it in, I find the following in syslog:

May 19 19:31:11 UBUNTUBOX kernel: [  179.096403] usb 1-1.2: new full-speed USB device number 5 using ehci_hcd

May 19 19:31:14 UBUNTUBOX pulseaudio[1678]: [pulseaudio] alsa-util.c: Unable to load mixer: Invalid argument

May 19 19:31:14 UBUNTUBOX kernel: [  182.207155] 5:1:1: usb_set_interface failed

There are loads of those usb_set_interface failed lines. Later on, I get the following when I use aplay -l to query it, I get more:

May 19 19:33:06 UBUNTUBOX kernel: [  294.021946] 6:1:1: usb_set_interface failed

May 19 19:33:06 UBUNTUBOX pulseaudio[2264]: [pulseaudio] module-alsa-card.c: Failed to find a working profile.

May 19 19:33:06 UBUNTUBOX pulseaudio[2264]: [pulseaudio] module.c: Failed to load module "module-alsa-card" (argument: "device_id="1" name="usb-ARCAM_ARCAM_USB_Audio_1.0_0000-00-A10" card_name="alsa_card.usb-ARCAM_ARCAM_USB_Audio_1.0_0000-00-A10" namereg_fail=false tsched=yes ignore_dB=no deferred_volume=yes card_properties="module-udev-detect.discovered=1""): initialization failed.

May 19 19:33:06 UBUNTUBOX pulseaudio[2264]: [pulseaudio] module-udev-detect.c: Tried to configure /devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2/1-1.2:1.0/sound/card1 (alsa_card.usb-ARCAM_ARCAM_USB_Audio_1.0_0000-00-A10) more often than 5 times in 10s

Running lsusb gives the following line for the rPAC:

Bus 001 Device 007: ID 25c4:0003

Typing aplay -l gives the following -- see card 1 below:

card 0: PCH [HDA Intel PCH], device 0: CONEXANT Analog [CONEXANT Analog]

  Subdevices: 1/1

  Subdevice #0: subdevice #0

card 0: PCH [HDA Intel PCH], device 3: HDMI 0 [HDMI 0]

  Subdevices: 1/1

  Subdevice #0: subdevice #0

card 1: A10 [ARCAM USB Audio 1.0], device 0: USB Audio [USB Audio]

  Subdevices: 1/1

  Subdevice #0: subdevice #0

So the rPAC device is obviously alive and recognized by some part of Ubuntu. Furthermore, the LED on the rPAC turns green from red when connected, indicating that it's activated.

So far, I've tried adding the following line to /lib/udev/rules.d so that libmtp (I'm on libmtp9, by the way) might recognize it:

# ARCAM rPAC

ATTR{idVendor}=="25c4", ATTR{idProduct}=="0003", SYMLINK+="libmtp-%k", MODE="660", GROUP="audio", ENV{ID_MTP_DEVICE}="1", ENV{ID_MEDIA_PLAYER}="1"

I also tried changing /usr/share/alsa/alsa.conf to give it a specific hardware slot (slot 1). But firstly, I get the following error:

cannot find the slot for index 1 (range 0-29), error: -16

and secondly, the rPAC light remains at red. So I've backed out my changes to alsa.conf.

If anyone's got any bright ideas, I'd very much appreciate it! I'm spending too much time banging my head against a brick wall!

Thanks,

James.