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ADAT expander query

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ADAT expander query

Postby nathanscribe » Sat Nov 02, 2019 6:36 pm

I'm thinking of adding an ADAT expander to my A&H Zed R16. The A&H has two ADAT ports out and two in. I'll be adding 8 channels, for a 24-track setup. Certainly I'll be using the extra inputs, but am undecided yet on whether I'll want extra outputs. Make and model of expander is not decided yet.

My first question is about clocking. From what I've read, both interfaces need to share a clock, though I'm a little confused about which device should be the master clock here – the A&H manual shows a diagram where the Zed can sync to either ADAT or computer. Is clock transmitted over the ADAT connection? The Zed only has ADAT ports, no extra word clock connectors. My hunch is the the expander would be master clock, is that right? Or would the Zed be clock, and I would connect both the in and out ADAT cables to clock the expander?

Secondly, do these extra inputs (and outputs if I buy an expander with those) appear as 'part of' the Zed in my DAW and Audio/MIDI setup menu on the Mac? Or are they an aggregate device? I've had trouble with aggregates before, so am reluctant to go that route again.

Cheers,

Nathan
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Re: ADAT expander query

Postby Hugh Robjohns » Sat Nov 02, 2019 7:59 pm

nathanscribe wrote:From what I've read, both interfaces need to share a clock, though I'm a little confused about which device should be the master clock here – the A&H manual shows a diagram where the Zed can sync to either ADAT or computer.

There can only be one master; everything else needs to be a clock slave.

Digital devices work best when running off their internal clock... but that's not an option when running multiple devices. Some digital devices perform just as well when running on an external clock, but not all do. Ideally, then, you'd make the box which performs worst on an external clock act as the clock master.... but that's not always a very practical solution, and workflow pragmatism generally overrules converter accuracy! :-)

In your case it would probably make most sense to have either the computer or the desk serve as clock master, and have the ADAT expanders as slaves.

Is clock transmitted over the ADAT connection?

Yes... but only in the same direction as the signal flow. So if your ADAT expanders are A-Ds only, then they can send a clock to the desk via the lightpipe connection, but you can't slave the ADAT expander to the desk that way... you'd need either a separate wordclock feed or it would need to accept another lightpipe input (so would have to be a D-A as well).

The Zed only has ADAT ports, no extra word clock connectors.

Boo.... not helpful...

My hunch is the the expander would be master clock, is that right?

Yes, that would work for a single expander... but not if you want to add two.

Secondly, do these extra inputs (and outputs if I buy an expander with those) appear as 'part of' the Zed in my DAW and Audio/MIDI setup menu on the Mac?

Yes. They are extra physical inputs to the Zed, and conveyed to the computer via the Zed's USB interface.

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Re: ADAT expander query

Postby nathanscribe » Sat Nov 02, 2019 8:23 pm

Thanks Hugh, much appreciated :)

Hugh Robjohns wrote:
nathanscribe wrote:Is clock transmitted over the ADAT connection?

Yes... but only in the same direction as the signal flow. So if your ADAT expanders are A-Ds only, then they can send a clock to the desk via the lightpipe connection, but you can't slave the ADAT expander to the desk that way... you'd need either a separate wordclock feed or it would need to accept another lightpipe input (so would have to be a D-A as well).

In light of your reply I've been back to the manual and what you said has clarified things. It looks like the Zed must use 'Firewire' as its clock source (there's a switch on the back for FW/ADAT clock select) when hooked up to ADAT expanders and using a DAW to record.

If I understand correctly, if that expander has both in and out lightpipes, I can hook them both up and that's enough to sync it correctly (settings notwithstanding).

Thanks again, just need to make sure to check the specs on the expander when shopping :)
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Re: ADAT expander query

Postby Hugh Robjohns » Sat Nov 02, 2019 8:37 pm

That makes sense... So the computer/DAW is the clock master. The zed slaves to that via its FireWire interface. And the expander(s) sync to the desk via their ADAT inputs -- so you will need expanders that provide outputs as well as inputs (such as the Behringer ada8200 -- although alternatives of higher quality are also available, of course...)

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