Connecting a Behringer UM2/UMC22 audio interface

Question

I'm looking for a not-so-expensive solution to get sound input into the Pi 3. As I'm a sound artist, this should have reasonable noise levels, and in the particular case I also want to amplify a microphone.

So I'm looking at the Behringer UM2/UMC22 (haven't figured out what the exact differences are except a 5 EUR price tag difference). Manual says they are USB class compliant. I assume that any class compliant USB interface should in theory work on the Raspberry Pi 3 (as on any other Linux box). Is that correct?

How about USB power. I'm a bit worried that the Pi might have trouble feeding such a device, as the general 2.5A power adaptors seem not that strong. On the other side, cheap USB sound interfaces never have an external power option. (I'll try to go for a dynamic mic and avoid +48V phantom power).

Should I insert an active USB hub? Should it work with bus power directly from the Pi nevertheless?

Answer 1

At work, we have used the Behringer UCA202 with the Raspberry Pi, (Pi 2 and Pi 3) with JACK, similar to what you'd set up for sound recording. It is powered from the Pi's USB ports.

Yes, it "should" be safe to assume that a compliant card should not draw more than the 500 mA specified for USB. If you have other stuff hooked up to USB it is always better to use external power, so that's yes to your first question too.

I have tested different external USB sound cards with the Pi, and the not-so-positive answer is that they sometimes work and sometimes not. That cards are USB compliant is no guarantee that they will work with Linux.

I have not tried the cards you mention and the difference seems to be design and the pre-amp chip. That may or may not be important for Linux compatibility. If you buy the card from a good dealer, ask them if you can check if it works and get an option to select another card if it doesn't (or get a refund). We've done that in our local shop, they tend to be helpful.

Another thing, the Pi does not like hot plugging USB powered devices. If you know you will do that, get a powered hub.