Is anybody running two interfaces connected via ADAT?

[Jim]

I'm trying to troubleshoot clicks I'm all of a sudden getting in my recordings. I have two Scarlett 18i20 interfaces. Thanks to the collective wisdom here, I found it simpler to run both interfaces from their own USB cables than use ADAT. It's been working great for about two years.

So, I put in a Support Ticket with Focusrite. Tech support said the clicking is probably from a sync issue due to two USB connections. I'm skeptical, but you don't get help from TS unless you do what they tell you to do.

So, I connected my two interfaces via ADAT, and tried to run both off of one USB cable.

But, DP doesn't see two interfaces in the Bundles or Configure Hardware Driver windows.

Hence my question whether anybody has gotten DP to recognize more than one interface via ADAT ganging. If so, what do you think I'm doing wrong?

[HCMarkus]

You will not see two interfaces on your computer when the second is an ADAT slave.

The primary interface that is attached via USB will publish all the I/O to the computer. So look for additional inputs under the primary interface for all I/O.

[Jim]

Thank you! I see my error now.

This is how my Bundles look with just one interface. It looks the same with both ganged by ADAT. I was expecting to see 18 more inputs.

When I moved the squares from the bottom two inputs (SB and RM) over to inputs 17 and 18, I'm getting all ten inputs into DP, as I desired.

Thank you. Thank you. Thank you.

[HCMarkus]

Glad you got it sorted, Jim!

[bayswater]

I'm skeptical, but you don't get help from TS unless you do what they tell you to do.

If you’re happy with the working setup, that’s great, but I’m skeptical too.

Was there a change in the Setup? It would have been set so that one of the two units was the timing master. Without that setting you might expect timing problems. I’ve never had problems with multiple USB units in DP.

I used to have two MOTU units connected by ADAT and that gave timing errors with a click every few minutes. You could see the slow drift in timing between the two units in the recorded waveforms. I used WordClock to connect the two and that fixed it. But I don’t think you can use that with the Focusrite units.

[Jim]

Was there a change in the Setup? It would have been set so that one of the two units was the timing master. Without that setting you might expect timing problems. I’ve never had problems with multiple USB units in DP.

I used to have two MOTU units connected by ADAT and that gave timing errors with a click every few minutes. You could see the slow drift in timing between the two units in the recorded waveforms. I used WordClock to connect the two and that fixed it. But I don’t think you can use that with the Focusrite units.

My setup hasn't changed since I started using the two interfaces on their own USB connection. What has changed is getting clicks in my recorded tracks.

The interfaces both have a Word Clock Out, but no In. The Focusrite site claims ADAT handles the clock. <https://focusrite.com/articles/all-about-adat/> So, I'm keeping those ports clear.

I've only done one three minute test recording with the ADAT ganging, and no clicks. But, they've come and gone randomly in the past, and I'll have to keep load testing this configuration before I can draw conclusions. The clicks seem to have come after recording my best take - Murphy's Law.

I'm going to put DP into record, and let it run for a while, then set the resulting clips' volume to +18 db. That ought to reveal any clicks.

Thanks again to HCMarkus and bayswater for their insight.

[HCMarkus]

Although ADAT will work for send/receive clock, I always prefer to use Work Clock if available. Keeps the clock stream independent from the litepipe audio stream. I can't say it actually improves anything in an audible way, but can say I've been doing it that way for years and have had zero clocking issues.

But I just took a look at the Scarlett 18i20 back panel... Clock OUT only, so WC won't work here, as bayswater noted. So disregard, Jim. I'll leave the post up as a pointer for others who might have an ADAT expander that offers Work Clock In.

[Phil O]

I'm not at all familiar with the Focusrite units, but when I was connecting my Apogee unit to my MOTU 828 there was a setting on the Apogee unit for clocking via ADAT. If this setting was wrong I would get clicks. Check your manual for similar settings. Also, I found that making your USB device (in my case it was Firewire) the master clock in DP's hardware configuration and slaving the added ADAT device off of the USB connected device gave stable results.

I am skeptical, however, about tech support's advice. I've never had a problem with multiple USB interfaces in DP. Just sayin'.

Your friendly neighborhood Phil

[HCMarkus]

I am skeptical, however, about tech support's advice. I've never had a problem with multiple USB interfaces in DP. Just sayin'.

Your friendly neighborhood Phil

For me, a big advantage of ADAT slaving is all inputs and outputs show up on a single interface's hardware mixer.

Not sure, but I seem to recall having multiple direct computer-connected interfaces increases latency, at least nominally.

[Jim]

I've done about ten 10-track, five minute recordings since reconfiguring to the Dual-ADAT mode, and so far, haven't gotten any clicks in my recorded tracks. So far, so good!

[bayswater]

That’s encouraging. My set up is very similar so I might try connecting another unit to my Focusrite via ADAT and see how it goes. Thanks for the update.