Do I need to care about word clock?

[bduersch]

Seemingly complex question, hopefully a simple answer...

I've recently been re-doing my studio to upgrade the ol' gear a bit. My new setup consists of a PC running Sonar Producer 4 with Frontier Design Dakota/Montana cards (capable of handling 32 channels of ADAT IO). I've got 3 rack preamps/converters: a Focusrite Octopre LE, a Presonus Digimax LT, and a Behringer ADA8000.

Here's the dilemma: The Montana card has BNC wordclock in. So does the Behringer. The Octopre and Digimax both have wordclock in & out. How can I chain 'em together to make them all co-exist peacefully? Based on what I've read so far, if the devices are internally terminated, it's not possible to use BNC T-connectors to chain everything together, right?

Is there anyway I can sync them using the optical cables and just ignore the BNC cables?

For what it's worth, I will use all 3 converters for recording, but will likely only use the Octopre for playback.

Thanks for any light you can shed on this!
--B

 

[James HE]

You should be able to link them all optically. I'm assuming the Dakota has 4 banks of ADAT in and out? Does each unit have ADAT in as well as out? If so, then simply connecting 3 outs from the Dakota into each unit and the 3 outs of each unit to the in on the dakota should work.

If everything is not on the same clock, it will be bad. You'll either have minor clictches or outright chaos. You can daisy chain Work Clock. The terminating (last) connection has to be 75ohms, and the connections in the middle have to be higher ohms. A wordclock distribution amp would be the most elegant solution though.

My Mackie 800R has only a wordclock in. There is a switch there so that you can switch it to be terminated at 75ohms. If any of those units have that feature, put that last in the chain. I believe you can also put a transformer on the end to terminate it, not positive though.

This is just an answer off the top of my head, I don't know if I really know what I'm talking about here. Intresting question though! I'll do a little digging and see if I can get a more solid reply.

 

[mshilarious]

The trouble with optical connections is that a device can't receive clock from an optical output. Thus the LT will be unhappy playing with other devices UNLESS it is master clock, or if it receives clock via the BNC connector.

I think I would be inclined to use the Octo as master clock, and connect the others via BNC. Read their manuals and see what they say about termination; I had a look at the LT manual as I used to have one, and it doesn't say anything. Even so I would give that a try, as BNC connectors aren't particularly expensive

 

[bduersch]

You should be able to link them all optically. I'm assuming the Dakota has 4 banks of ADAT in and out? Does each unit have ADAT in as well as out? If so, then simply connecting 3 outs from the Dakota into each unit and the 3 outs of each unit to the in on the dakota should work.

Yeah, in taking a closer look, both the Behringer and Focusrite have ADAT in and out (since they're AD/DA converters), while the Presonus only has ADAT OUT (technically only an AD converter). If I make the Presonus the master, could it send ADAT sync to the sound card, then let the sound card pass it along to the Focusrite & Behringer?

If everything is not on the same clock, it will be bad. You'll either have minor clictches or outright chaos. You can daisy chain Work Clock. The terminating (last) connection has to be 75ohms, and the connections in the middle have to be higher ohms. A wordclock distribution amp would be the most elegant solution though.

As far as I can tell, each device has a provides termination on its BNC connector, all 75 ohms (ok, I know how to disable termination on the sound card, but that's the one place where I actually want termination). But I've got a handful of BNC cables and T-connectors, so there's no harm in trying.

I did consider a wordclock distribution amp, but looks like most of them are most expensive than my converters, which seems a little hard to justify at this point. Although I did spot a Hosa 4-channel word clock generator for like $80... that probably falls into the "too good to be true" category. Still, for $80, it's probably worth trying out, just to see if it can be the master to the Frontier card and the 3 converters.

--B

 

[bduersch]

Ok, I sent messages to Behringer, Focusrite, and Presonus tech support last night, and here's the response I got from Focusrite:

The Octopre LE BNC input is termnated with a 150Ω to ground
resistor. if you are going to chain the octopre it would make sense not
to have the Octopre at the end of the chain.

Since the Octopre LE has both AD and DA converters, I was actually thinking about putting it first in the chain and using it as the master clock for both recording and playback. Sounds like it may be better suited to being in the middle of the chain.

Now if I can get a response from either Presonus or Behringer about how their BNC connectors are terminated, I should be ready to rock.

--B

 

[mshilarious]

Since the Octopre LE has both AD and DA converters, I was actually thinking about putting it first in the chain and using it as the master clock for both recording and playback. Sounds like it may be better suited to being in the middle of the chain.

If you are using it as master, it doesn't matter how its input is terminated, because you aren't using it.

 

[lpdeluxe]

ADAT Lightpipe works for carrying word clock as long as the master is "upstream" (the source of the signal) and all the slaves are "downstream" (being fed the signal). I use a digital mixer as the master, and the sound card is synched to it; I have a preamp with fiberoptic I/O, and when I use it, the return from the sound card is used as the source of word clock. Since I have two sound cards linked via a synch cable, this works. I also use a HOSA ADAT patchbay, which allows me to split the return from the sound card and send it to digital devices for synch purposes.

It's easier, if you have gear that is sometimes in the data stream and sometimes out of it (like my preamp, which isn't used all the time) to get a word clock distribution amp. I use a Lucid CKX6. I can run a BNC cable from the master to it, then send word clock to up to 6 devices, regardless of whether they are "downstream" from the master or not. For example, I have a second digital mixer that I use to route signal to a pair of playback speakers and two headphone amps: I don't have to worry about any trick routing because I can plug a BNC from the Lucid into its word clock In, sync to that, and be done.

 

[James HE]

I posted another response last night, but it got eaten. The server seemed to dissapear when I hit submit.

I'll save myself some time and try to keep this one short. lol.

I think that you should try this. Use the focusrite as your clock master. Feed it's BNC clock output to the presonus clock input, thru that from the out and into the Behringer. I think I read somewhere that the Behringer in is 75ohms. You could use a T in there Before the Behri to feed the Dakota, but I think that you'll be better of simply syncing the Dakota to the focusrite via ADAT optical. That is if the Dakota can be switched to slave to one of it's ADAT optical input. (should be able to) I'm pretty certain you'll be good this way, I have been wrong before though! Basically you should be able to output clock from the octopre thru the BNC out and the optical out at the same time. So you can do a mix of both to simplify the setup as much as possible.

 

[bduersch]

Use the focusrite as your clock master. Feed it's BNC clock output to the presonus clock input, thru that from the out and into the Behringer.

That's an interesting idea, and something I was wondering about. If a device like the Presonus or the Focusrite is a "slave", what does it send through its WC out? Same thing it receives through its WC in? (That's what I'm inferring from your suggestion)

Hopefully whis will become immediately obvious once I have time to sit down with a bunch of cables and experiment. Right now I've got the Behringer at the house, and the Presonus & Focusrite are in shipment. So my goal is to pick up a few cables this week so that I can spend Saturday trying out all the possibilities.

This really has been helpful... I've never had to deal with word clock given the interfaces I've used in the past, so I'm learning as I go.

--B

 

[lpdeluxe]

I would think that the WC out sends whatever it is synched to, whether internal (master) or external (slave). That's how most of my gear works, except that the preamp I mentiioned insists on being the master when the S/PDIF out is used (with ADAT Lightpipe, it will happily accept external clock).

 

[pingu]

Seemingly complex question, hopefully a simple answer...

I've recently been re-doing my studio to upgrade the ol' gear a bit. My new setup consists of a PC running Sonar Producer 4 with Frontier Design Dakota/Montana cards (capable of handling 32 channels of ADAT IO). I've got 3 rack preamps/converters: a Focusrite Octopre LE, a Presonus Digimax LT, and a Behringer ADA8000.

Here's the dilemma: The Montana card has BNC wordclock in. So does the Behringer. The Octopre and Digimax both have wordclock in & out. How can I chain 'em together to make them all co-exist peacefully? Based on what I've read so far, if the devices are internally terminated, it's not possible to use BNC T-connectors to chain everything together, right?

Is there anyway I can sync them using the optical cables and just ignore the BNC cables?

For what it's worth, I will use all 3 converters for recording, but will likely only use the Octopre for playback.

Thanks for any light you can shed on this!
--B

Ive yet to see a definite answer on this topic.

A lot of pros seem to be undecided on the matter.

Do a search here

http://recforums.prosoundweb.com/index.php/f/38/13127/?SQ=34af92327a5280ffde1eaa8ac9d283bc

 

[bduersch]

Yea! I got the following response from Presonus (which was helpful):

They are self terminating, yes… the outputs are not passive ‘thru’ outs, they are active repeaters. I do not know the resistance of the BNC connection. I assume it behaves the same as a 75ohm-resistor terminator plug; nonetheless I have heard from people who own an Apogee Big Ben and the BB seems to not indicate that the unit is not terminated until a terminator is attached to it’s outs. This did not affect performance, however.

So the active repeater sounds like a good thing... the Digimax sounds suited to being in the middle of the chain.

Then I got the following response from Behringer, which didn't entirely answer my questions:

Use the WC in connector to connect devices for the external synchronization of your ADA8000. This BNC connector is only active, when the respective setting on the rear is made. When, for example, various devices are interconnected in a digital recording system with, say, a digital mixing console, all digital units connected have to be synchronized via a shared wordclock signal.

The setting of the switch depends on the application of your ADA8000. If an external ADAT recorder is supposed to send the wordclock signal (in this case, the ADA8000 functions as the slave), the switch has to be set to the ADAT in position. Please also note the instructions given in the user's manual of your ADAT device. When your ADA8000 functions as the master (here, the ADA8000 sends the wordclock signal) please use the switch to select the sampling rate of your choice (either 44.1 or 48 khz).

Sounds like the Behringer is capable of sending wordclock, but when hooked up to my Frontier card, it claims no wordclock is being sent. When the Digimax/Octopre get here I'll be able to troubleshoot to see if it's an issue with the Frontier card or the Behringer (or perhaps the cable).

--B

 

[mshilarious]

Sounds like the Behringer is capable of sending wordclock, but when hooked up to my Frontier card, it claims no wordclock is being sent. When the Digimax/Octopre get here I'll be able to troubleshoot to see if it's an issue with the Frontier card or the Behringer (or perhaps the cable).

--B

You probably need to tell the Frontier to clock to the Behri's ADAT signal.

 

[bduersch]

Ok... here's a few more details from Behringer support...

The ADA8000's BNC word clock input is designed to be used with standard 75 ohm BNC coaxial word clock cables (as opposed to 50 ohm 'video'/CATV BNC cables). The BNC input is a high-impedance design that is NOT equipped with an internal terminating resistor - so if you are running your word clock connection to a 'chain' of multiple devices you should use 'T' connectors and a termination resistor ("BNC terminator plug") on the last device. If the last device in your chain has an internal terminating resistor it is not necessary to use a 'T' connector and BNC terminator plug on the last device. That said, the majority of our users with smaller setups (such as the ADA8000 being the one device slaved to a word clock source) often don't bother with 'T' connectors or BNC terminator plugs, and don't experience a problem...but in a larger setup with the same BNC word clock run 'daisy chained' to multiple devices, it will be more important to do it the 'correct' way.

Considering that, today I rigged things up with the Presonus as the master, ran BNC from the Presonus WC out to a T-connector on the Behringer, then continued running BNC to the Frontier card WC in (which is internally terminated). Seems to be working well so far--one thing I like about the Frontier Dakota driver (control panel) is that it has indicators that light up when sync errors occur, and the indicators stay lit until manually cleared, so I can easily see that there have been no sync errors for several hours since I wired everything up.

The Focusrite will arrive early next week, but I don't think I'll have any problems making the Focusrite the master then sending the WC downstream to the Presonus, Behringer, and Frontier card by BNC.

--B

 

[bduersch]

Yea! Well, I'm glad to report that the Focusrite arrived this week, and I got it racked up last night. As anticipated, I made it the master clock device, running the BNC through the Presonus (with the active repeater) through the Behringer (with no repeater/termination) to the Frontier card (which is internally terminated). Everything sounds great, and based on the Frontier drivers, it looks like there have been no syncing issues since wiring everything up.

Thanks to everybody for their help in figuring this out... in the past I've always used cards that kept themselves in sync (Delta1010LT's, Firepods), so the world of ADAT and word clock was entirely new to me. The additional complication was well worth the end result. So thanks again!

And nothing would be complete without a picture of the new rack, which is pretty much complete from a "I really don't need any more gear" perspective:

http://studio.naughtybutterspoon.com/studio._rack2.jpg

--B