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Trouble with using old MOTU 2408 to add analog inputs

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Trouble with using old MOTU 2408 to add analog inputs

Postby Panas1 » Sat Jan 13, 2018 8:20 pm

Hello, knowledgeable SOS folks. I wonder if anyone can clue me up here.

I mix my hardware synths on a Mac using a Focusrite Saffire Pro 40 interface, which sounds great and works well. I decided to add 8 more analog inputs to this.

After reading around I couldn't get any solid info on whether I could successfully daisy chain another Pro 40 to the first one via Firewire, so I decided to go the optical ADAT route instead. Being on a low budget, I decided to try the cheapest possible option :clap: which was an old MOTU 2408 ....
Unfortunately it seems that the MOTU does not send clock sync down the 8-channel ADAT route. The audio comes into the Saffire's ADAT inputs with added crackles and noise, even though the Saffire indicates that it has locked onto the MOTU. When I tried the SPDIF coaxial connection it works fine, and so does using the optical as SPDIF- but of course these routes only give two channels. It is also not possible to sync the MOTU to the Saffire as the MOTU will apparently only accept clock over optical or SPDIF when using those digital inputs and you cannot use the digital & analog inputs at the same time in standalone mode (needs a PCI card to use with a computer).
I already tried another optical cable with no luck.

Do I have to get something like an ART SyncGen to sync both units? The MOTU has a word clock input and an "External" clock setting which can be selected regardless of where the audio is coming from. The Saffire has an SPDIF input. So the SyncGen would clock the MOTU over word clock and the Saffire over SPDIF.
Will this work? Or am I better off getting a more recently made A/D 8-channel box ?

Thanks!
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Re: Trouble with using old MOTU 2408 to add analog inputs

Postby James Perrett » Sat Jan 13, 2018 11:25 pm

Double check your settings - the ADAT stream definitely has an embedded clock and your Focusrite should be able to sync to it. Check that it isn't something silly like the optical input being set to SPDIF (had that happen to me a few weeks ago).
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Re: Trouble with using old MOTU 2408 to add analog inputs

Postby Panas1 » Sat Jan 13, 2018 11:37 pm

Thanks. I will triple-check :smirk: but I'm pretty sure that wasn't the case as I tested the "Use Optical SPDIF" option in the Saffire.
I'm wondering if I should try a more expensive optical cable. The second one I tried is made by Fisual and had lots of positive reviews on Amazon, but cost less than £10....
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Re: Trouble with using old MOTU 2408 to add analog inputs

Postby Panas1 » Mon Jan 15, 2018 1:04 pm

I managed to get it to work by using a coaxial SPDIF cable to clock the Focusrite from the MOTU. It worked for about half an hour before the crackling came back.... Rebooting the MOTU didn'd help.
The optical cable I am using has a stiff braided sleeve and is just long enough so it took some effort to twist it around to be able to plug it in at both ends. It seems that the cable is under some tension (torque?) when in position. Could this be the issue?
I found someone else online describing the exact same problem with these two devices, but no solution was offered. :headbang:
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