Is the clock in Sync HD better than MTRX?

[mkoetter]

Hi there. I have a HDX system that has 1 HDX card connected to a MTRX on the port 1 (with an HD IO on exp port) and an HD IO on port 2 (with another HD IO on exp port).

I assume the MTRX has the best clock, so I am using that to send WC to all 3 HD IO’s and some outboard gear.

I just inherited a Sync HD. Does this have a better clock, or can it improve the way I distribute clock to this system?

[devinemke]

Originally Posted by mkoetter

I just inherited a Sync HD. Does this have a better clock, or can it improve the way I distribute clock to this system?

I can't speak to the quality of the clocks, but the Sync HD + HD I/Os all have "loop sync" BNC ports that might simplify your clock distribution. You patch the loop sync out of the Sync HD, then through the HD I/Os, then lastly back to the Sync HD to close the loop. The MTRX does not have loop sync so you just patch Word Clock from the Sync HD -> MTRX. Then the Sync HD becomes the clock master for all of your gear (as set in your Pro Tools Session Setup window).

Remember to patch the serial cable from your Sync HD to the HDX card for proper communication between your array of I/O and Pro Tools.

This is exactly how my rig is set up. I have 2 x MADIs rather than HD I/Os, but it's the same clock patching arrangement.

Hope this helps.

[Darryl Ramm]

If you don't the video sync capabilities of the Sync HD then there is really no reason or benefit to use it. Just keep using the MTRX as the clock source. Heck if you don't need it sell it and buy some more MTRX cards etc.

[BScout]

MTRX has a better clock. Send MTRX clock to Sync HD and then have any other Avid devices loop sync from the Sync HD. Tell the Sync HD to follow the Mtrx word clock inside ProTools. Then the Sync HD acts as a word clock distributor.

If you don't need video sync satellite, gen lock picture, or LTC generation/output, there is no point in adding a SyncHD

[mkoetter]

I don’t have video needs, so I can remove the sync HD from the system.

That said, should I send MTRX WC to my loop sync master, or send WC from the loop sync master to the MTRX?

[Darryl Ramm]

The MTRX is likely best so send clock from that to other devices.

Always do what BScout says

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The other side of this is I doubt I or most others could hear any difference. And so it's likely not that important. Always interesting to see if you can hear a difference,... in a blind test.

To me what is important is making sure you use good quality 75 ohm BNC digital cables, that won't fall apart of people touch them (and stop people touching them anyhow). I use a different color cable (orange) for clock cables to help with cabling.

Getting unneeded stuff out of your rig is a good idea, just help keep stuff simple and more reliable. And maybe it' worth selling the Sync HD.

[BScout]

Originally Posted by mkoetter

I don’t have video needs, so I can remove the sync HD from the system.

That said, should I send MTRX WC to my loop sync master, or send WC from the loop sync master to the MTRX?

You are either using loop sync or external sync but not both. (because if the interface is loop syncing, it is ignoring the external sync.)

Send the MTRX clock to all your interfaces and set each interface to listen to external sync word clock. If you have only 2 interfaces besides the MTRX, you can do this with a 75 ohm BNC T connector to split the word clock signal. If you have 3, then you'll probably be fine with two T connectors and short cables. If you need to clock 4 devices, you need a clock distributor. Do not cable the loop sync BNC connectors in this case (it confuses Pro Tools)

[mkoetter]

Thanks! Really appreciate the suggestion. I’ll get some T connectors. Already have a bunch of short HQ 75ohm BNC’s.

FWIW I did manage to get the HDIO to send WC to the MTRX by setting the MTRX WC termination to Hi Z (as opposed to 75 ohm). But if the MTRX has the best clock, I’ll go with that!

[BScout]

Make sure, once set, all the HD IO units show the ext clock light on from the front.

If you aren't used to this kind of setup, it's a little confusing how Avid made this but you have to go to Session Setup, where it says "clock source", and toggle through each hardware interface (other than the MTRX) to select ext word clock. Whichever one you toggle last will also get the loop sync master light but that means nothing if the loop sync cables aren't connected.