clocking MADI SSL Delta/Alpha link and Digi 96io

[Matt_Gio]

hey,

I've recently hooked up a Digi 96 io with my SSL converters so that I can use it for headphone sends but am getting what sounds like clocking glitches when recording.. they are not coming up on the audio files though.

I am running PT HD2 pci-e on mac pro.

MADI between Delta and Alpha Link
Delta Link into HD Core via digi cable
96io into HD accel via digi cable

Clock out of Alpha Link into 96io
Clock out of 96io into Delta Link

Clock set internal on PT.

does this sound right to everyone??
thanks
kindest
Matt

[Sammas]

I would have thought that the clock for the delta link and 96 would be set to external in protools as they are both being clocked by the alpha link. Some gear can be pedantic about termination as well.

[Matt_Gio]

hrmm im pretty sure the manual set to set PT clock as internal?

[Sammas]

The manual says the delta link must be clocked by an external source:

4. Synchronization
Pro Tools® HD card
The Pro Tools® HD card is designed to operate as a Clock Slave, locking to a clock reference signal provided by the audio unit connected to its primary port.

Delta-Link MADI HD
The Delta-Link MADI HD, like the Pro Tools® HD card, is designed to operate as a Clock Slave. Once the card and Delta-Link MADI HD are connected together, they can be seen as a unit requiring an external clock reference signal. However, this unit now has MADI ports, instead of the “Digital and Analogue” connections to other devices provided by Pro Tools® interfaces.

Although a reference signal is embedded in the Primary port, the MADI connection requires a separate WordClock signal. Therefore, the Delta-Link MADI HD is equipped with a WordClock input connector.
Depending on the type of unit that is connected to the MADI port, the sample rate will no longer change automatically when a setting is selected in the PC or Mac software (because there is no command channel). Therefore, the sample rate must be set manually at both ends (in the Pro Tools® software and on the hardware connected to the MADI port).

Only 1 device should be set as the master clock. If you are running the wordclock from the alpha link to the 96 and delta link, the alpha link is your master clock. It would have its clock source set to internal and all the other devices set to receive external clock.

[Matt_Gio]

oh crap.. do I maybe have to set the 96io clock as external in the hardware setup window of pro tools??

Ive never had to do that before when running a 96io with lynx aurora i suppose cause you could run a sync loop with those units??

M

[Matt_Gio]

loop sync maybe?

should that work in/out word clock of Alphalink to Loop sync in/out of 96io and then wordclock out of 96io to delta link?

M

[Sammas]

Hey Matt!
That is the way I would try it first. Wordclock out of the alpha link to loop sync in of the 96. Loop sync out of the 96 to wordclock in of the delta link. Set the alpha link to internal clock, and both the delta and 96 to external within the protools hardware setup menu (I forgot what it actually says. Perhaps it is "wordclock" rather than external).

Keep in mind though that with it set like this, you need to match your protools session sample rate to the sample rate set on the alpha link - protools won't automatically changed the sample rate of sessions. If you want to record at 48khz, you need to set your alpha link to 48khz and also create a session at 48khz.

Let us know if this clears up the clicks and pops.

[Matt_Gio]

cool!

at moment I have it running..

Alpha link Loop Sync out INTO 96io loop sync in
96io loop synch out INTO Alpha link loop sync IN

96io WC out into Deltalink WC in

seems to be working ok.. but is this how you are supposed to use loop sync?

M

[The Tasmanian]

Yes - its confusing but that sounds right.
I'm doing similar with 192's clocking off Mytek 192's.
Its all about the master clock being the clock source.
"loop" sync, suggests that it has to go around in a loop - this is confusing.

[Sammas]

whoooops! A bit of a mess up on my part. There are two sets of BNC I/O on the back of a 96. One is loop sync, the other is wordclock. Loop Sync is only for chaining multiple digidesign HD I/O together.

Don't use loop sync when clocking from external sources, use the External wordclock in & out connections. When the 96 is correctly clocked from the Alpha link, the "EXT" led will light on the front panel. You will need to select external word clock in protools still.

[The Tasmanian]

But that does not make sense to me... I'm confused now..

I've had 3 HD rigs that have all had Mytek 192 convertors at the front end, and every tech I know, and sound devices etc have always told me to go clock out into the loop sync in - but then I was using the Sync i/o after the Mytek clock out, and before the Digi 192's - maybe that is the difference?
Confusing stuff clocks....

[Sammas]

Bah! I hate digital clocking. Loop sync is a derivative of digidesign's superclock, innit? Its meant to be run as a loop (hence the name) when running multiple HD interfaces - daisy chaining output to the next units input and so one, then the last unit's output goes back to the first units input to complete the loop.

That being said, I have no idea how a Sync I/O fits in the mix... and I actually think Loop Sync runs at 1x rather than 256x like superclock does... so it probably works just the same. Somewhere in there has to be 256x superclock to allow people to use legacy Protools Mix interfaces.

Another method would be to use a BNC T-connector on the word clock input of the 96 and not use its wordclock/loop sync output at all. That way both the Delta link and 96 get the original paralleled clocking signal from the alpha link.

but you know what they say.

...If it ain't broke.

[gigpiglet]

from my understanding (which may or may not be correct, but its what i thought/ learnt) is that its ALWAYS best to use a T adapter, and only use the IN on all the devices
never using any "through" or "out" apart from the master

but im also a bit like nath says... if its connected, and it works, and it never clicks or pops.
then its all good!

[The Tasmanian]

Ive never seen a HD / or 96 I/O set-up with a T used anywhere, ever, - in any studio Ive been in around the world.
I think we are starting to confuse the poor man.

This is the set-up on every Protools rig Ive seen.
This is also the way every top tech I know does it, including Lewis ex Sound Devices.
If anyone in this country knows what they are doing with Protools hardware clocking, it is Lewis:

Master Clock out >
into Sync I/O clock in >
Sync I/O loop sync out >
192 #1 = loop sync in > then loop sync out >
192 #2 = loop sync in > then loop sync out >
192 #3 = loop sync in > no termination, - no loop back to anywhere.

It works, everything clocks, never misses a beat, and Ive run 3 HD rigs this way for more than 10 years.

The idea is - loop sync is not a whole system loop - it is for going in and out of digidesign hardware.
It works this way with the 96 i/o too.
I'll leave you guys to try and re-invent / argue over the clock set-ups that have been proven to work.

If you use the above set-up as a template for clocking, you will not have any problems - change it and you will.

[gigpiglet]

to be fair - i was not talking about pro tools hardware.
i have never used it.
i was just talking about wordclock and digital devices.

PT is black magic man.... i stay right away from it.

[Sammas]

Ive never seen a HD / or 96 I/O set-up with a T used anywhere, ever, - in any studio Ive been in around the world.
I think we are starting to confuse the poor man.

This is the set-up on every Protools rig Ive seen.
This is also the way every top tech I know does it, including Lewis ex Sound Devices.
If anyone in this country knows what they are doing with Protools hardware clocking, it is Lewis:

Master Clock out >
into Sync I/O clock in >
Sync I/O loop sync out >
192 #1 = loop sync in > then loop sync out >
192 #2 = loop sync in > then loop sync out >
192 #3 = loop sync in > no termination, - no loop back to anywhere.

It works, everything clocks, never misses a beat, and Ive run 3 HD rigs this way for more than 10 years.

The idea is - loop sync is not a whole system loop - it is for going in and out of digidesign hardware.
It works this way with the 96 i/o too.
I'll leave you guys to try and re-invent / argue over the clock set-ups that have been proven to work.

If you use the above set-up as a template for clocking, you will not have any problems - change it and you will.

Hey Chris!

The 192 manual actually suggests that if you are clocking a system externally to use the wordclock I/O as Loop Sync is only for HD peripherals. This would appear to be the plan if running the alpha link as master. There is a lot of arguments for running t-connectors and 75-ohm termination plugs in this instance.

Loop Sync is definitely designed to work in a system loop as the name suggests. The rationale is based on the software control that loop sync's implementation provides. If you have 10 HD interfaces in a system, and they are all correctly sync'ed in a loop you can freely change via protools which HD interface is the Loop master, and the remaining 9 become loop slaves. Setting an interface to be loop master interrupts the loop sync signal seen at its input. You can't do this with 10 Apogee 16x interfaces via standard wordclock... at least not via software... you can via lots of button pushing!

LOOP SYNC In and Out
Loop Sync is a dedicated clock loop for synchronizing multiple Pro Tools|HD peripherals together (multiple audio interfaces, and/or a Digidesign SYNC I/O and one or more audio interfaces). Loop Sync uses a word clock signal
based on sample rates of either 44.1 kHz or 48 kHz. As sample rate increases in the system,
Loop Sync continues to operate at a base rate of 44.1 kHz or 48 kHz, depending upon the higher rate.

The Loop Sync In and Out ports are standard BNC connectors that output a 1x Loop Sync
clock signal. Loop Sync should only be used to chain multiple Pro Tools|HD peripherals together.

EXT. CLOCK In and Out
The External Clock I/O ports are standard BNC connectors that receive and output a word clock
signal. These ports can be used to synchronize the 192 I/O to any device that requires (or provides) word clock.
External Clock In and Out are configured by your choice for Clock Source in Pro Tools.