10 Jan
2019
10 Jan
'19
4:42 a.m.
On Wed, 9 Jan 2019, Bob van der Poel wrote:
Hey, me again. Back at it ... same problems :) But, I
_think_ I figured out the
problem ... it's the USB port. If I use the "easy to get at port", I'm
using a
USB3, and it creates the problem. If I use a harder to reach port, USB2, all
works fine. Don't need to use pasuspender, don't need to turn off pulse audio
ports, etc. Just run audacity and it all works.
To recap, I'm using a Presonus Audiobox USB connected to my PC and running
Audacity to do some simple recording. The USB3 port gives me scrambled recordings
... the USB2 port works fine.
So, do I have a bum port or is this normal?
Totally normal., Most mother boards do this two ways:
- one of your USB ports is probably connected to IRQ16 for legacy
purposes, along with two or three other internal bits.
- even if that is not the case, it may have an internal hub and be
sharing that port with another physical USB plug (with your
mouse?) or even an internal mic or whatever.
I had a laptop (netbook?) with one USB on the left and two one the right.
To get stable sound, I had to use one of the right hand USB ports for
audio and leave the second right hand empty and put a hub on the lefthand
side to use with everything else. The lefthand USB was also used
internally as well as being irq16 while the two on right were from the
same hub (so I could only use one) but had a clear irq.
Also, some MB have bios settings for irq choosing. It may be possible to
allow the MB to asign USB or other irqs or not (or leave certain irq
unassigned). I have found that letting the Linux kernel assign the irq
rather than bios gives a more inteligent assignment. If you have a desktop
with spare slots, I would get a PCIe USB card and use that USB for audio
only... trying different PCIe slots to find the one that works best.
Finally, if you use the rtirq script at boot.... it may seem nice to do:
"usb, snd, whatever" but you may be better doing: "usb2, snd, whatever,
usb" to make sure that your audio IF is actually higher priority than your
mouse (assuming you are using USB2 for audio). I have an old ice1712 in a
PCI slot (yes I found a new MB with 3 PCI slots in it) and so put
"snd_ice, snd_ens, etc" because my ensoniq sound card can not be before
the ice or it interferes with it (and I am only using the ensoniq for it's
MIDI ports).
Some of these tweaks may be less needed if you use an RT kernel, but I am
using a lowlatency kernel and these kind of tweaks allow me to run the
ice1712 with jack at 16/2 and no xruns (so long as pulse is not bridged,
pulse is fine down to 64/2 though... 128 with skype).
--
Len Ovens
www.ovenwerks.net