Need help connecting external FX through S/PDIF


I am having troubles setting up my routing for my studio.
I have Cubase 5 and my sound card is a MOTU 828 MkII which has optical ins/outs.
I want to set up a TC Electronic M350 as an external effect through SPDIF. I went to external FX and set a bus (the output of my soundcard goes into the optical input of my TC M350 and the return of the effect goes back into the optical input of my MOTU). However i get no sound back into my DAW. The signal goes into the M350 from the card (i can see the leds of my M350 lit up so that means that it recieves the signal from my MOTU), but the problem is that nothing is coming back through my return bus into the DAW.

Am i doing something wrong ?
Any help is much appreciated

EDIT : when i click the delay loop compensation button the signal comes back, so theoretically it is supposed to work, but i get no sound when i play my track

Speaking from the old days of experience, using an external effects processor with a Tascam multi-track tape machine. Consider breaking things down to the very the ‘basics’ …typically, you’d use a physical ‘Effect Insert’ I/O routing to send out from an audio track(s) into the effects unit input, and then out of the effects unit output, back into the I/O of your ‘Effect Insert’ connection.

I’m guessing you’re simply routing it wrong somewhere…within your Motu, or within your host software. 1st off, I’d double check that you’re sending & receiving signals properly from your audio tracks as an ‘Effect Insert’, and also from within the Motu’s software control panel, be sure you’re proper routing your s/pdif signals In & Out.

On my Aardvark Q10, I had a hell of a time getting the s/pdif to send & receiving properly. Believe it or not, it wasn’t as intuitive as the audio routing I was used to. The problem I had of not working was all me, within my sound card routing of the s/pdif. Now that I know how, it’s easy. I have no idea of how your Motu control panel is set up, but in my Aardvark Q10, my s/pdif go’s In and Out of digital channels 9 & 10 (coaxial connections), and is shared/duplicated on analog audio channels 7 & 8…that is, the signals in digital s/pdif channels 9 & 10, can be heard/listened to through audio channels 7 & 8 …which is one way to test/verify my signals. My Q10 also has a ‘test tone’ feature to verify signal routing.

With the above, you should verify your signals somehow. You say you see activity in your effects unit, can you verify that there is any signal coming back out of it? My guess is that you’d have to be able to monitor (listen) to the FX’s s/pdif output from your Motu, because it’s a digital signal. Maybe you can try to use the FX’s units analog Outputs, by way of speaker monitors, or headphones directly connected to it to listen for a signal coming out. Does your FX’s unit also have meters to see if it’s sending any signal out?

When you confirm that the FX’s unit is actually sending a signal out, you need to verify your Motu is actually receiving it…which by the way, you should verify that your s/pdif cables are working properly at this time. Are you actually using digital coaxial cables for s/pdif, or regular RCA cables/connectors? How long are the runs? Do you have spares to test against? Can you swap cables for the I/O to compare? I just ordered 2 more new 3 ft long digital s/pdif HOSA cables from ebay, and was delivered within 3 or 4 days.

Back within your host software, verify you’re sending & receiving from your Effect Insert channels properly. I haven’t really used much external effects since I’ve been doing computer recording mind you, and as for buses, I’ve stuck to the very basics without exploring complicated signal routing (only what I need), I’ve never used many features in Cubase in this area, so I’m not the most experienced when it comes to Cubase routing & buses. The purpose of my reply is only to make you think about what you’re doing and how you’re doing it, and to consider to ‘basics’ for troubleshooting. This is how I approach things when troubleshooting, taking it ‘point by point’ and verifying things along the way. Somehow, you’ve lost it along a point…or two :bulb:

Just yesterday, I spent a handful of hours experimenting with routing digital s/pdif signals in various ways between 3 computers via their audio interfaces…it really get’s confusing. By the way, I use computers as my ‘outboard gear’ these days.

Thank you so much for your time, i really appreciate ! I’ll check some ideas. The problem is clearly between the TC350’s out and MOTU’s coax in, because like i said, i can monitor the signal and i know it’s coming into the FX unit because of the input LEDs. Thanks

EDIT : Both cables are working correctly. It’s wierd because in Cubase i can check the delay compensation of the effect in the External Routing (and since the way it works is by sending a signal back and forth, it means that the DAW recieves actually something from the M350)

I have had a TC m300 hooked up to a Motu 828mkII via spdif. Worked great, but took me a little while to get going. I’m not anywhere near the computer and won’t be for months, but I remember that I had the spdif turned down in the motu mixer, I could record it but not monitor it. Took me a minute or 60 to figure out the problem was in the Motu mixer. It definitely works it’s just a setup issue.

Although I don’t use the exact same gear as you I thought I would post my settings hoping that it might give you some insight which you can apply to your own situation.

Delta 1010LT.
Master clock = S/PDIF IN
S/PDIF sample rate = 44,100
S/PDIF output format = Consumer
Routing = H/W out S/PDIF =Wave out S/PDIF

Cubase VST Connections.
Inputs = Do Not add S/PDIF in to input bus
Outputs = Do Not add S/PDIF out to output bus
“Add to external FX bus”
External FX Send L & R M-audio Delta ASIO = 9 & 10 S/PDIF out Delta 1010LT
External FX Return L & R M-audio Delta ASIO = 11 & 12 Mixer in Delta 1010LT

REV2496 V-Verb Pro.
In/Out Master Input = Digital
Digi = 44.1 khz
Input source = XLR (I use an RCA to XLR adapter)
Dither = Off
Output Format = S/PDIF

Hi guys
I have same problem with cubase 5 and tc electronics M350 FX processor
I conect TC Electronics M350 with my audio interface Focusrite saffire pro 40 via S/PDIF then in CUBASE 5 i made external fx - sends = s/pdif 1&2 , returns =s/pdif 1&2 then I add to audi track fx channel and put there tc electronic measure delay and it works but my problem is that now all audi channels start working through this fx channel even those ones which is not signed to this fx channel , I understand there is mistake somwhere in routing …anybody can help me to resolve this problem?
Thanks K.