Hi, I seem to have an issue with USB soundcards on my laptop. I have tried two of them, but I keep getting crackling sounds while playing with Ardour or Hydrogen. Everytime this crackling sounds occur, I get the following in dmesg: ALSA urb.c:480: frame 5 active: -18 The Kernel is 2.6.39 with Irqthreads, Alsa is the git version (1.0.24). I have tried a lot of things already, but I'm really ready to restart the investigation from scratch and to provide any information! Thanks in advance for the help. dmesg details: [ 41.927872] CE: hpet2 increased min_delta_ns to 7500 nsec [ 41.927897] CE: hpet2 increased min_delta_ns to 11250 nsec [ 75.569991] CE: hpet5 increased min_delta_ns to 7500 nsec [ 75.570003] CE: hpet5 increased min_delta_ns to 11250 nsec [ 79.234811] ALSA urb.c:480: frame 1 active: -71 [ 102.065990] CE: hpet4 increased min_delta_ns to 7500 nsec [ 102.066005] CE: hpet4 increased min_delta_ns to 11250 nsec [ 147.964992] ALSA urb.c:480: frame 5 active: -18 [ 185.833311] ALSA urb.c:480: frame 4 active: -18 [ 271.091937] ALSA urb.c:480: frame 1 active: -18 [ 276.686711] ALSA urb.c:480: frame 1 active: -18 [ 300.120588] ALSA urb.c:480: frame 0 active: -18 [ 302.416319] CE: hpet increased min_delta_ns to 30169 nsec [ 318.225546] ALSA urb.c:480: frame 7 active: -18 [ 318.433469] ALSA urb.c:480: frame 7 active: -18 lsusb -v gives (only the details about the soundcard): Bus 001 Device 003: ID 0763:2080 Midiman M-Audio RunTime DFU Device Descriptor: bLength 18 bDescriptorType 1 bcdUSB 2.00 bDeviceClass 0 (Defined at Interface level) bDeviceSubClass 0 bDeviceProtocol 0 bMaxPacketSize0 64 idVendor 0x0763 Midiman idProduct 0x2080 M-Audio RunTime DFU bcdDevice 1.51 iManufacturer 1 M-Audio iProduct 2 Fast Track Ultra iSerial 0 bNumConfigurations 1 Configuration Descriptor: bLength 9 bDescriptorType 2 wTotalLength 340 bNumInterfaces 5 bConfigurationValue 1 iConfiguration 0 bmAttributes 0xc0 Self Powered MaxPower 0mA Interface Association: bLength 8 bDescriptorType 11 bFirstInterface 0 bInterfaceCount 5 bFunctionClass 255 Vendor Specific Class bFunctionSubClass 1 bFunctionProtocol 0 iFunction 2 Fast Track Ultra Interface Descriptor: bLength 9 bDescriptorType 4 bInterfaceNumber 0 bAlternateSetting 0 bNumEndpoints 0 bInterfaceClass 255 Vendor Specific Class bInterfaceSubClass 1 bInterfaceProtocol 0 iInterface 2 Fast Track Ultra ** UNRECOGNIZED: 0b 24 01 00 01 34 00 03 01 02 03 ** UNRECOGNIZED: 0c 24 02 01 03 06 00 08 03 00 00 00 ** UNRECOGNIZED: 09 24 03 02 01 01 00 01 00 ** UNRECOGNIZED: 0c 24 02 03 01 01 00 08 03 00 00 00 ** UNRECOGNIZED: 09 24 03 04 03 06 00 03 00 Interface Descriptor: bLength 9 bDescriptorType 4 bInterfaceNumber 1 bAlternateSetting 0 bNumEndpoints 0 bInterfaceClass 255 Vendor Specific Class bInterfaceSubClass 2 bInterfaceProtocol 0 iInterface 0 Interface Descriptor: bLength 9 bDescriptorType 4 bInterfaceNumber 1 bAlternateSetting 1 bNumEndpoints 2 bInterfaceClass 255 Vendor Specific Class bInterfaceSubClass 2 bInterfaceProtocol 0 iInterface 0 ** UNRECOGNIZED: 07 24 01 03 01 01 00 ** UNRECOGNIZED: 14 24 02 01 08 03 18 04 44 ac 00 80 bb 00 88 58 01 00 77 01 Endpoint Descriptor: bLength 7 bDescriptorType 5 bEndpointAddress 0x01 EP 1 OUT bmAttributes 5 Transfer Type Isochronous Synch Type Asynchronous Usage Type Data wMaxPacketSize 0x0138 1x 312 bytes bInterval 1 Endpoint Descriptor: bLength 7 bDescriptorType 5 bEndpointAddress 0x82 EP 2 IN bmAttributes 1 Transfer Type Isochronous Synch Type None Usage Type Data wMaxPacketSize 0x0003 1x 3 bytes bInterval 1 Interface Descriptor: bLength 9 bDescriptorType 4 bInterfaceNumber 2 bAlternateSetting 0 bNumEndpoints 0 bInterfaceClass 255 Vendor Specific Class bInterfaceSubClass 2 bInterfaceProtocol 0 iInterface 0 Interface Descriptor: bLength 9 bDescriptorType 4 bInterfaceNumber 2 bAlternateSetting 1 bNumEndpoints 1 bInterfaceClass 255 Vendor Specific Class bInterfaceSubClass 2 bInterfaceProtocol 0 iInterface 0 ** UNRECOGNIZED: 07 24 01 02 01 01 00 ** UNRECOGNIZED: 14 24 02 01 08 03 18 04 44 ac 00 80 bb 00 88 58 01 00 77 01 Endpoint Descriptor: bLength 7 bDescriptorType 5 bEndpointAddress 0x81 EP 1 IN bmAttributes 5 Transfer Type Isochronous Synch Type Asynchronous Usage Type Data wMaxPacketSize 0x0138 1x 312 bytes bInterval 1 Interface Descriptor: bLength 9 bDescriptorType 4 bInterfaceNumber 2 bAlternateSetting 2 bNumEndpoints 1 bInterfaceClass 255 Vendor Specific Class bInterfaceSubClass 2 bInterfaceProtocol 0 iInterface 0 ** UNRECOGNIZED: 07 24 01 02 01 01 00 ** UNRECOGNIZED: 14 24 02 01 08 03 18 04 44 ac 00 80 bb 00 88 58 01 00 77 01 Endpoint Descriptor: bLength 7 bDescriptorType 5 bEndpointAddress 0x81 EP 1 IN bmAttributes 5 Transfer Type Isochronous Synch Type Asynchronous Usage Type Data wMaxPacketSize 0x0138 1x 312 bytes bInterval 1 Interface Descriptor: bLength 9 bDescriptorType 4 bInterfaceNumber 3 bAlternateSetting 0 bNumEndpoints 2 bInterfaceClass 1 Audio bInterfaceSubClass 3 MIDI Streaming bInterfaceProtocol 0 iInterface 5 Fast Track Ultra MIDIStreaming Interface Descriptor: bLength 7 bDescriptorType 36 bDescriptorSubtype 1 (HEADER) bcdADC 1.00 wTotalLength 63 MIDIStreaming Interface Descriptor: bLength 6 bDescriptorType 36 bDescriptorSubtype 2 (MIDI_IN_JACK) bJackType 1 Embedded bJackID 1 iJack 0 MIDIStreaming Interface Descriptor: bLength 6 bDescriptorType 36 bDescriptorSubtype 2 (MIDI_IN_JACK) bJackType 2 External bJackID 2 iJack 0 MIDIStreaming Interface Descriptor: bLength 8 bDescriptorType 36 bDescriptorSubtype 3 (MIDI_OUT_JACK) Warning: Descriptor too short bJackType 1 Embedded bJackID 3 bNrInputPins 1 baSourceID( 0) 2 BaSourcePin( 0) 1 iJack 8 MIDIStreaming Interface Descriptor: bLength 8 bDescriptorType 36 bDescriptorSubtype 3 (MIDI_OUT_JACK) Warning: Descriptor too short bJackType 2 External bJackID 4 bNrInputPins 1 baSourceID( 0) 1 BaSourcePin( 0) 1 iJack 0 Endpoint Descriptor: bLength 7 bDescriptorType 5 bEndpointAddress 0x07 EP 7 OUT bmAttributes 2 Transfer Type Bulk Synch Type None Usage Type Data wMaxPacketSize 0x0008 1x 8 bytes bInterval 8 MIDIStreaming Endpoint Descriptor: bLength 5 bDescriptorType 37 bDescriptorSubtype 1 (GENERAL) bNumEmbMIDIJack 1 baAssocJackID( 0) 1 Endpoint Descriptor: bLength 7 bDescriptorType 5 bEndpointAddress 0x87 EP 7 IN bmAttributes 2 Transfer Type Bulk Synch Type None Usage Type Data wMaxPacketSize 0x0008 1x 8 bytes bInterval 0 MIDIStreaming Endpoint Descriptor: bLength 5 bDescriptorType 37 bDescriptorSubtype 1 (GENERAL) bNumEmbMIDIJack 1 baAssocJackID( 0) 3 Interface Descriptor: bLength 9 bDescriptorType 4 bInterfaceNumber 4 bAlternateSetting 0 bNumEndpoints 0 bInterfaceClass 254 Application Specific Interface bInterfaceSubClass 1 Device Firmware Update bInterfaceProtocol 0 iInterface 7 M-Audio DFU Device Firmware Upgrade Interface Descriptor: bLength 9 bDescriptorType 33 bmAttributes 1 Will Not Detach Manifestation Intolerant Upload Unsupported Download Supported wDetachTimeout 2000 milliseconds wTransferSize 1024 bytes bcdDFUVersion 1.10 Device Qualifier (for other device speed): bLength 10 bDescriptorType 6 bcdUSB 2.00 bDeviceClass 0 (Defined at Interface level) bDeviceSubClass 0 bDeviceProtocol 0 bMaxPacketSize0 64 bNumConfigurations 1 Device Status: 0x0001 Self Powered