[LAD] USB audio interface

[Ralf Mardorf]

Hi,

in December 2016 I bought a B-Stock Presonus AudioBox 1818VSL for
309.00 €, but I send it back, because it didn't work with iOS. It works
with Linux. In January 2017 I bought a brand new Focusrite Scarlett
18i20 2nd Gen for 382.00 €. It works with Linux as well as with iOS and
allows lower latency than the Presonus.

Neither the headphone amp of the Presonus, nor the one of the Focusrite
could compare to my PCIe RME card, but sound quality of all IOs is as
expected for pro-sumer devices. You won't get a professional audio
device for <= 500.00 €.

My recommendation is the Focusrite. Behringer devices are less
expensive, but since reviews mentioned power supply issues, I wouldn't
buy one, even if they should sound good and if they should work with
Linux OOTB. With other Behringer gear I experienced power supply issues
myself.

Consider to buy a Focusrite, test it and return it if you aren't
satisfied [1]. If you could wait, you might get a special offer for less
than 400.00 €, too, the regular price is > 450.00 € at the moment.

For that price range the Focusrite IMO is a good choice. If you could
spend more money, a Babyface with an ADAT device much likely is a
better choice. FWIW I've got an ADAT device, the Focusrite could be
extended by ADAT and S/PDIF, so if you use both, you get 18 inputs and
20 outputs.

https://d2zjg0qo565n2.cloudfront.net/sites/default/files/focusrite/downloads/31605/scarlett-18i20-2nd-gen-user-guide.pdf

It's perhaps better to send such a request to Linux Audio User, than to
Linux Audio Dev.

Regards,
Ralf

[1] It doesn't make sense to say more about the Focusrite, since you
never know if all devices work in the same way. It's said that the
Presonus should work with iOS, but for me it doesn't. It's said that my
RME card should work with Linux, but it does cause issues, IOW not
everything works. So if I would spend time to write more about the
Focusrite, it might not be helpful, since it might be different, if you
use the device.

[Ralf Mardorf]

PS: You mentioned live usage. If you use a 19" rack it doesn't
matter, if you chose a Presonus AudioBox 1818VSL or a Focusrite Scarlett
18i20 2nd Gen, but if you carry the device in a bag, it might be
important, to be aware that the Presonus is smaller, but it has got an
external power supply. The power supply is also small.
However, the Presonus requires more power via USB, than the Focusrite,
it's within the standard, but some portable computers might need an USB
hub, if they should limit USB power to safe energy.

[Rafael Vega]

I own a Presonus Audiobox 1818VSL which worked just fine on an older
macbook running Arch Linux. I switched computers recently and the Presonus
gets a lot of xruns on this new computers. I saw some posts that suggest
that unit is not compatible with USB 3 ports.
https://linuxmusicians.com/viewtopic.php?f=6&t=13093&sid=d57c684ef372ed2a28fd487f102cc690#p57256

Post by Ralf Mardorf
PS: You mentioned live usage. If you use a 19" rack it doesn't
matter, if you chose a Presonus AudioBox 1818VSL or a Focusrite Scarlett
18i20 2nd Gen, but if you carry the device in a bag, it might be
important, to be aware that the Presonus is smaller, but it has got an
external power supply. The power supply is also small.
However, the Presonus requires more power via USB, than the Focusrite,
it's within the standard, but some portable computers might need an USB
hub, if they should limit USB power to safe energy.
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https://lists.linuxaudio.org/listinfo/linux-audio-dev

[Len Ovens]

I own a Presonus Audiobox 1818VSL which worked just fine on an older macbook
running Arch Linux. I switched computers recently and the Presonus gets a lot of
xruns on this new computers. I saw some posts that suggest that unit is not
compatible with USB 3 ports.
https://linuxmusicians.com/viewtopic.php?f=6&t=13093&sid=d57c684ef372ed2a28fd487
f102cc690#p57256

My understanding is that this particular problem is that it is a hardware
problem with some of the Intel MB chipsets (not the cpu itself). The first
thing to check however, is what else in your new computer is using the
same usb port, or the same irq. Some people have better luck removing the
USB3 driver and running the USB3 as USB2. Some have done better just
adding a PCIe USB card (in a desktop). Rumour is NEC USB chipsets work
better... but it could be just using a PCIe card on a fresh irq too.

--
Len Ovens
www.ovenwerks.net

[Bengt Gördén]

The first thing to check however, is what else in your new computer is
using the same usb port, or the same irq.

Definitely. I had to move my Soundcraft MTK 12 around a bit until I
found a port that wouldn't give me loads of xruns.

check with lsusb (lsusb -t) to see where it is now.

You could also do a "cat /proc/interrupts | grep -e usb -e CPU" to see
where you have all the interrupts going on at the moment. To the
interrupts in real time do a "watch cat /proc/interrupts".