Samuel540
I've been trying to get an optical signal into my Focusrite 18i8 but so far, none of the devices I've tried has worked. Most recently, I've been trying to connect the optical output of my PC's soundcard to the 18i8 audio interface but I haven't had any luck.

Is this even possible? If it is, what needs to be done to get this working?

Though the toslink port is the same, ADAT Lightpipe (8-channels of 44.1/48k) and optical S/PDIF (two channels) are different formats.  If you can switch the Focusrite's toslink port to "optical S/PDIF" (instead of Lightpipe), it'll work.
 

In Toms Post #8  it clearly shows his Fireface USB output via the Stereo ADAT.
That is not using the on board connection.
Well meaning, but not accurate. The INPUT to SONAR is the optical signal from the MB;
into the RME via lightpipe.
The screen shot (above) clearly shows I have selected Stereo ADAT as the INPUT.
As always Jim is absolutely correct, and I missed it, the RME recognizes that the input is SPDIF
as illustrated below.

Input Status SPDIF
But again, as always, "why am I not surprised?"
Its an RME; I don't remember having to select SPDIF, evidently the RME just "knows".
'nuff said
T
 

AH,, but I see it say's WDM mode. Is this correct?  I'm just basing my comment on the fact that you cannot access 2 sound cards under ASIO, but as I said, if your in a different driver mode which can be WDM or now we have WASAPI you can access the 2 audio devices. 
I also find it weird that it says Stereo ADAT? I thought ADAT was 8 channels only. 
Based on what Jim has stated above  shouldn't it say stereo SPDIF? 

Options just informs you what you "can" do; I'm running ASIO drivers.
The MB Realtek has nothing to do with SONAR.
It is my playback device for Windows (this is my office rig, on the StudioCat I have one of the headphone
outs on the UFX handling Windows, BUT that output is not "active" in SONAR).
IIRC the OP has never let on what he wants to record, I assume YouTube or something.
In the Studio I could lightpipe the 8 inputs on my Tascam 1884 (now just my control surface) into the RME.
I don't record drums, so I don't need the extra inputs.
As Jim stated above, if the Focusrite will recognize the SPDIF the OP is "golden". If not; he's SOL.
Well, he could go RME.
"You use RME, don't you wish everybody did?"
 
T
 

RME gear is expensive...
But it's nice to never have to give your audio interface a second thought.
It just works...
 
Sort of the Mercedes Benz of audio interfaces...  
 

DeeringAmps
Its an RME; I don't remember having to select SPDIF, evidently the RME just "knows".
'nuff said
T
 

That's good on RME!