[LAU] USB audio interface and a buggy USB controller

[david]

Philipp Überbacher wrote:
> Excerpts from david's message of 2010-09-15 19:32:44 +0200:
>> Monty Montgomery wrote:
>>> Oh, I should say I've also just recently seen similar problems (for no
>>> apparent reason) when an XHCI (3.0) controller hands off a full-speed
>>> (1.1) isochronous device.  Is the port this is being plugged into a
>>> USB 3.0 port ('SuperSpeed')?
>> Someone said something earlier about hubs. I have a USB2 hub plugged 
>> into a USB2 port on my laptop. When I tried using a Behringer UCA-202 
>> (USB1.1) device through the hub, it could barely play, and not record at 
>> all. Connected directly to a USB2 port, it plays and records fine.
>>
>> So original poster just might be dealing with an internal hub.
> 
> That usb hub stuff seems to be really strange. I do have an external
> hub, but I only use it for HDs.
> The USB interface is connected directly to one of the laptops ports.
> 
> The laptop seems to have an internal hub, or two?
> Anyway, it works just fine, as far as I can tell. Some jack2 test I ran
> showed quite immense jitter, but I guess that's normal with USB devices.
> 
> $ lsusb
> Bus 007 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
> Bus 006 Device 002: ID 0582:0074 Roland Corp. EDIROL UA-25
> Bus 006 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
> Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
> Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
> Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
> Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
> Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

jack2 on my non-RT kernel laptop has no jitter at all working with 
UCA-202 connected to a USB2 port on the laptop.

Lower signal levels and noise when connected via my self-powered 9-port 
USB2 hub. Cheap hub, probably very bad ground or poor shielding.

-- 
David
gnome at hawaii.rr.com
authenticity, honesty, community