Updating as I’ve talked to flatmax, and turns out the RxD pin is in fact not connected to the 40 pin connection extension on this board. That’s why I had MIDI through and out working (the TxD pin is connected!).
I have my work cut out for me now. Solder a small patch wire to bridge that pin (it’s not relevant to this specific board). Plug everything. And then, 
.
Goooooooooood 
It’s alive!!
@wyleu don’t want you to wait for any masterpiece (because it’s unlikely it’ll come soon 
). I just let a quick sequence go from my beatstep (I know, zynthian has its own now, but this was done during my lunch time after soldering and assembling everything, so… Hope it counts!)
I’m noticing something on the audio that I didn’t spot on my monitor speakers - there’s a very audible zzz sound throughout. Did some snooping and it seems it is there (my headphones make it a lot clearer), and its mostly due to the audio input jack not being plugged to anything on the other end. Is this supposed to happen?
(Otoh, this is proof that audio input is indeed working too! Hehe)
Got a lot to work on now, from getting the audio cleaner (power supply, likely) to shoving everything into the enclosure, adding them 4 switches and making it usable as a desktop first-class citizen like its predecessor was. But want to thank you all for the support and encouragement!
So if I understand correctly, I just doubled the population of audioinjector isolated on zynthian, right?
Couldn’t help myself, I had to know. Here’s a shorter rendition (as if it’s an actual piece rather than a bunch of fat-fingers pressed keys) of the same sequence - this time without the audio input saturator layer I had forgotten I’d added to test the capture 
Yes folks, the isolated DAC does actually sound really good, clear, unlike the previous clip might have led you to believe!
Excellent!
Nothing like a recording to get one to really listen to what is going on…
I don’t know what number of audio injectors plugged into zynth’s there are. For a while it was the only way to get audio in to the zynth.
Certainly I have to of them amongst my flock, The pedal board is probably the more relevant, but I’m tending to use a UMA 1820 as my input device at the moment, primarily cos it gives me suitable sockets for guitar and Mic & the multiple audio in’s allow me to jam against youtube videos whilst recording on the zynth, play them back overdub them ( in’s and outs need marking 
to stop hesitant pickups) and smash them down to oggs for sending to other people to practice against.
I’ll get back to the pedalboard soon and then the audio injector will get a little more love 
I meant the Isolated DAC+adc board, specifically, though.
I’ve also got one of those UMC 1820, but I’m planning on getting everything routed via patchbay, to be able to pull what I want into the zynthian, computer, etc. Not as versatile as applying effects on the zynthian for 8 different audio tracks at a time, but it’s more than enough for me home-studio wannabe tinkerer.
That said, this is a never-ending story, I know I’ll never be fully satisfied with my setup
sadly not got one of those.
I’ll be honest, this Kickstarter happened when I got interested in having that audio in on zynthian. Didn’t have the 1820 then - and didn’t realise I’d be stalling this for over a year 
. Glad I got it though!
[edgargoncalves]
Hi Edgar, Did you test the soundcard already with the latest stable?
I have a working setup with an Audioinjector ULTRA and wanted to replace it. Unfortunately it won’t show as device even in alsamixer.
When I put it back into an old V1 system, the soundcard is seen.
So I am wondering what your experience is.
Cheers,
Markus
All good.
It has been the ribbon cable. The Isolated has two options…from top or bottom. And the cable that I used with the ULTRA needed to be reversed. Or the 40pin (male) are defect on the board. Taking the cable for the female GPIO worked.
Hence I can confirm that the Isolated still works with the latest build.
Glad you sorted it @mheidt , as I swapped that DAC for a usb Scarlett that I had lasting around a while ago. Primary reason being I didn’t have enough space in the current enclosure (something I need to change one day anyway, but I’ve been lazy/settled with the black plastic box I have now). Yes, I lost the individual mixer levels on the new UI, but on the other hand it has physical knobs in a front panel that do basically the same, maybe more convenient even. And usb output has been feasible for my needs, no xruns.
Maybe when I finally decide to move the Zynthian into a eurorack panel, I’ll get that audioinjector back. Meanwhile, it’s gathering dust. (If anyone is interested, message me).