I have a Focusrite Saffire Pro40 and an old MOTU 2408. The MOTU is no longer useable as an audio interface but still works as an A/D converter. So I want to add 8 analogue inputs to the focusrite by connecting the MOTU with an optical cable.
The problem is that it looks like I have to sync the focusrite to the MOTU, but when I set the MOTU to 48 KHz I get noise. 44.1khz works fine. Any clues? Can I sync the MOTU to the focusrite with another cable in this use scenario? I get the impression that the MOTU will only sync to an external clock when you feed it with digital audio which is not the case here, as I’m just using its analogue inputs.
You probably need a BNC word clock cable as well, not sure if ADAT sends clock. Also check if the MOTU has any settings regarding it listening to external clock rather than internal.
Thanks. The MOTU manual is a bit too brief on the subject. I’ll try connecting an SPDIF cable (the saffire has no word clock connectors) and see if the MOTU will sync to it.
What I don’t get is why 44.1khz works fine (with the Saffire synced to the MOTU via the optical cable) but 48 does not… the audio comes in with a lot of digital noise. I guess it’s a limitation of the MOTU 2408 which came out back in 2000 or something 
(the mk1 model).
when you change the MOTU to 48 and you start getting noise, what does the Focusrite control panel say about the Pro 40’s clock state and sample rate?
I have personally experienced the Focusrite Control Panel software incorrectly indicating the actual hardware state. I always solved this by a restart of my Pro26 and the software. ( the MOTU may not be the root cause of your issue )
Ok, thanks, I’ll check. I do not like the Saffire Mix Control software.
(the mk1 model).