Oh, indeed @Vindes is right, I checked the specs of the Octopre Dynamic which has both ADAT input and ouput and there is also an Octopre (not Dynamic) which has only ADAT input. So, @Dextroze, take care.
They also have an higher model called Claret++ Octopre, while others Octopre are Scarlett Octopre…
Oh no…I bought it 
Which one? The good one or the bad one? 
Ahh shit!!! Can you cancel the deal? I noticed they had even older models all with Octopre in the same and all with different specs… not easy…
No it was a used one 
I should have looked better !
I saw ADAT for me that was all 
If you have any idea of what I should buy that’s not too cheap quality wise !
As I said, this one is really correct : BEHRINGER ULTRAGAIN DIGITAL ADA8200
But if you can resale the Octopre, you could also find a used Octopre Dynamic for not too much.
e.g. this guy could accept to split his bundle, it would be easier from him to sale only the audio interface:
https://www.leboncoin.fr/image_son/2192216198.htm
The Behringer one David-san mentioned is the least expensive option I’m aware of for an 8-in 8-out. Not sure where you are but this link has it at Thomann in Germany for 211 euro.
From what I’ve seen of these devices, moving up in price usually gets you better mic inputs. I’m not sure there will be much of an audible difference on the output D/A converters. I’ve always found the Behringer devices I’ve owned to be better quality than the prices would suggest and the build quality pretty good.
If you wanted to stick to RME, they have a few OctaMic options, but in the area of 10x the price of the Behringer.
Thank you guys for your help and support !
I feel less stupid and alone thanks to you 
I followed the link @Dextroze provided. In the pictures I see input and output. For ADAT as well.
Or do I misunderstand?
Update: it has two ADAT outputs. I must be blind, I think
It is easy to misunderstand what these devices exactly do. The Octopre (not dynamic) has line out jacks because I think you can use them as preamp outputs without using the ADAT. But if you check the specs this model has only AN conversion and only ADAT outputs, which clearly means that @Vindes is right.
Exactly and I am not sure they have something similar, i.e. 8 Line/MIC preamp inputs and 8 outputs in the same unit.
Yep. Your right. 2 * adat out, for 192 khz I assume.
And amazingly low latency drivers
Yes, and the good news with these ADAT extensions is that whatever their brand (Behringer, Focusrite…), if the audio interface is an RME, you stay with the RME drivers.
Yes, I think that’s the most important point to understand. Neither the computer, the drivers, or the Baby Face know what device is on the other side of the ADAT interface. From reviews of the ADA8200 the latency added by going through the ADAT should be well below 1ms.
If it were me, and price mattered, and this were to be used primarily in a live environment, primarily for extra outputs, the Behringer ADA 8200 would be an easy choice.
In contrast, if one were going to use this in a studio environment to add extra mic, line, and instrument inputs for recording, this would not be my unit of choice. That said, a Baby Face obviously isn’t intended to serve that role either, so if that were my goal I’d pick a whole new interface rather than try to expand the Baby Face through ADAT.
I went through exactly this search several years ago when looking to expand the I/O of my Baby Face Pro. For my use, at the time, there was no option that made sense for me. I ended up buying an RME UFX II and moving my Baby Face to a different computer.
But like I said, if I were looking primarily for extra outputs for live use, the Behringer fits that bill.
I have got one on my RME UCX. For studio work, with two MIC and two instrument preamps, my UCX is enough. And for live situation I use the ADA 8200 for mixing the band and having more stage monitoring possibilities. The Midas Mic preamp of the ADA 8200 seems enough to me for the back singers in live situation. And everything goes through RME TotalMix where and I feel at home. When I bought the ADA 8200 I didn’t found the Octopre Dynamic or Claret + Octopre and for my live use, I didn’t want to consider high-end RME extensions. That’s why I first proposed this device to @Dextroze, while the Claret+ Octopre could possibly be an improvement and it has also two additionnal instrument jacks.
Question…could a mixing table do the job ?