I’m looking for a USB Soundcard (small if possible) with SPDIF working on Linux, any recommendations?
Focusrite Scarlett 8i6, maybe? But the first or second generations. The 3rd gen is not yet supported in Linux.
It seems that you cannot access internal mixer or PAD switch on that one.
I can’t speak for the second generation, but from what I’ve been told by users here and on the gearslutz forum, is that the second generation should be fully functional. As for the first generation, you can access every facet of the mixer via ALSA (via the terminal line or using one of the GUIs for ALSA). I’ll have to get back home to check which ALSA GUI I use but it was one of the ones that comes standard with Ubuntu Studio. There’s no feature in the first generation Scarlett line that you can’t access in Linux, but you do have to poke around a little. Alternatively, all the ASIO controlled parameters in those interfaces get saved to the soundcard, so if you doubleboot or otherwise have access to a Windows machine, you can always set these parameters to your liking in Windows and then when you go back to Linux, the settings will be saved as you set them.
But I am using a first generation 18i20 on Linux exclusively and I recently started using the SPDIF output to feed my PreSonus Monitor Station v2. After playing around a little in ALSA I was able to adjust the output gain on the SPDIF and get everything up and running just fine. I think its worth a try. Plus the first gen units are dirt cheap nowadays on the used market.
Take a look at the Behringer UCA 222 (or 202). They’re USB, work with Linux, have SPDIF and are pretty cheap. I haven’t tested SPDIF, but I can test it during the weekend for you, if you want.
I have the scarlett 2gen 18i20, And for me this driver works out of the box with ubuntustudio 18.04 LTS stock kernel and newer. Internal HWcontrol(mixer) does’nt work though. But, there is a work in progres on putting Geoffrey Bennetts driver into the kernelsource tree. (Kernelversion 5.4 I believe) https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/sound/usb/mixer_scarlett_gen2.c?h=next-20190904. For now, you can only get his versions of this driver from a fork https://github.com/geoffreybennett/scarlett-gen2 . There are many people using this driver including my self and its working. otherwise you can do dualboot as @Samm R Sany said. That works too. but its not optimal.
Cheers 
1 Like
Thanks, as I can see the UC222 it has only output SPDIF, and the first generation scarlett is only USB1 so I think I’m going to check the second gen with that driver you posted.
First gen scarlett is USB 2.0. At least my 18i20 is.
If you only need SPDIF, you can check the USB Streamer (https://www.minidsp.com/products/usb-audio-interface/usbstreamer-box) which can be used with ADAT or SPDIF firmwares, among others.
I really like my Behringer UMC1820. Fantastic value really. It’s as slim as they come for interfaces with 8 preamps. If you could also entertain desktop PCI card options my other choice would be the Audiophile 192 that also works flawlessly out of the box in Linux. Obviously at this point you’d be relying on eBay to source it. However, sticking to USB as per your post, I don’t think you can go wrong with the Behringer unit (and unlike its smaller siblings, the UMC1820 actually has a power button).
This one looks big for a laptop. 
I take your point. It is small for how much is packed in (well not as impressively small as the Zoom F6!) but I’m struggling to think of anything else that has SDPIF in and out for such a good price. SDPIF in/out seems to mostly only appear on interfaces with more preamps (at least that I can see in the prosumer market).