Hello everybody, I have been testing several scenarios to find some glues why some usb audio devices did not fully work and gave stuttering sounds I found the following: usb devices define a max power attribute during there enumeration process. I have some usb devices that have this at 500mA and some that have this on 100mA. I also have some usb hubs that have external extra power supply and some that are only a hub with bus power. Here it comes: Make sure the 4 port usb hub is full with for example: - usb keyboard (100mA) - usb mouse (100mA) - usb audio (100mA or 500mA) - usb stick (200mA/500mA) - usb hub with external power (500mA MaxPower) (AC adapter delivers 1A) - usb hub without external power (100mA MaxPower) Make sure to use audio with several tones low tones (most dvds will do) When connecting a 100mA usb audio devices on a hub with external power it will give stuttering sound!! (most usb audo devices are 100mA and most hubs are external powered due to more then one usb stick) When connecting a 500mA usb audio device on a hub with external power it will work perfectly. When connecting a 100mA or a 500mA usb audio device on a hub without external power it will work perfectly. I have the idea there is something wrong with the power distribution system when using external powered usb hubs... Any ideas how to correctly address this problem/bug? Best regards, Jelle _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
