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How best to clock: Let's separate fact from myth. Digital Converters
Old 27th November 2006
  #1
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Matthew Murray's Avatar
 

How best to clock: Let's separate fact from myth.

My current chain involves an Aurora 16 feeding a fireface 800 with ADAT. The fireface is getting the Aurora's master clock signal via the ADAT connection. Very simple.

But now I'm adding another fireface 400, and either a Crane Song Hedd or a UA 2192. I'd rather the Hedd, but the reason I was considering the 2192 is because it has 4 clock outputs and could act as a master clock for all my gear.

This seems like a silly reason to buy one piece of gear over another, and it leads me to ask this question:

If I've got a Hedd, two firefaces, and a lynx aurora, how would I best clock them? I'd want to be using the Hedd as the master.

•The Hedd would be connected to the fireface 400 via SPDIF
•The Aurora 16 is connected to the fireface 800 via ADAT

Can the clock signals be distributed completely via the digital connections, and reliably? Or is it better to chain all this gear with BNC cables? I've heard that chaining clock cables is a bad idea for some reason.

Or, should I do the simple thing and just get the 2192, because all the other options aren't reliable?

Thanks as always.
Old 27th November 2006
  #2
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frans's Avatar
With my limited knowledge i would suspect that chaining cables would introduce a slight delay to the signal further down the line that could perhaps end up as a framing error. Duh.
Old 27th November 2006
  #3
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d_fu's Avatar
 

Quote:
Originally Posted by Matthew Murray View Post
Can the clock signals be distributed completely via the digital connections, and reliably?
In principle, yes. But you can only have one devce as clock master. For covenience reasons, I'd choose the FF800 for the purpose, then all the others will follow when you change sample rates.
For this to work, all connected devices would need SPDIF or ADAT inputs also to receive a clock signal from the FF800. In the absence of such inputs, you'd have to use Word Clock.
Old 27th November 2006
  #4
Shoot outs

The best way to do it is fairly boring, labor intensive and difficult.

It would be to try ALL the various configurations to find the one which sounded best..

But the problem with clock 'shoot outs'...... is the time it takes between each different set up, means you can 'forget' the sound of the last set up.. This make comparisons 'difficult'

I find these shoot outs are best done with a golden eared friend..

Anyhow a simplistic view is to take the clock signal from the most expensive unit and distribute that all round your studio to the other equipment...

For this reason I can see why the UA unit is tempting and the extra clock outputs on it is are a clever feature...

There are many companies making inexpensive clock distribution units perhaps use one of those to send the Hedd clock around your studio?

Presumably the Hedd will be your 'golden channel' used for all overdubs and two key elements when multitracking and using all the converters at once?
Old 27th November 2006
  #5
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Chaining clocks does not introduce a delay. It's not like chaining midi devices, where you do get problems. In fact, there are those that say that chaining WC is better than going through a distribution box. I do both in my studio, and I can tell you with complete certainty that you can either chain or distribute the WC and either works fine if done properly.

There was a *huge* thread about this over at prosoundweb a while back. Guys like Dan Lavry and Bob Katz were weighing in on the issue, and there was plenty of technical info being discussed. A very informative thread, I suggest you do a search for it.
Old 27th November 2006
  #6
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Matthew Murray's Avatar
 

I think I'd most rather use the Hedd for clocking, not the fireface. It's probably the best one of the lot.

Jules -- yes you're right, the Hedd is for all overdubs as well as the two key channels (ie. overheads) when tracking drums or other multi-tracking. The "try every method" is time costly yes, and I'd rather just pick a solution that works. I doubt that the differences between methods are that huge anyways -- but the reason for my question is ultimately to ensure that something like "chaining" isn't going to cause errors or jitter or anything awful like that.

Albert ... I'd love to read this thread you mention but I can't hunt it down on prosoundweb. Does anybody know what this thread was called or have a link to it?

Thanks all for your help thus far.
Old 27th November 2006
  #7
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SnakeCained's Avatar
 

BNC word clock chaining is fine if you use the correct T-bars and Terminate properly.

Any mistakes in this can introduce propogation delay and potentially clock jitter.

However a good converter will re-sync the incoming clock to suit it.

If I had a penny for every screw up clock system I'd seen inc. the worlds greatest studios...............

You could always post a sketch of what your planning.
Old 27th November 2006
  #8
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max cooper's Avatar
 

Matthew:

Try this one:

http://recforums.prosoundweb.com/ind.../t/14324/9014/



Better make some tea, prop up your feet and take the phone off the hook. It's a doosy.
Old 27th November 2006
  #9
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danasti's Avatar
 

Quote:
Originally Posted by Matthew Murray View Post

But now I'm adding another fireface 400, and either a Crane Song Hedd or a UA 2192. I'd rather the Hedd, but the reason I was considering the 2192 is because it has 4 clock outputs and could act as a master clock for all my gear.

This seems like a silly reason to buy one piece of gear over another, and it leads me to ask this question:
What's the main reason that you are adding either the hedd or 2192?
Old 27th November 2006
  #10
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Matthew Murray's Avatar
 

Hot damn Max, thanks for the link. That's going to take a long time to read.

As for a sketch of what I'm planning.. if I'm using BNC daisy chain, I guess it's basically:

Hedd => Aurora => Fireface 400 => Fireface 800.

I presume I can simply daisy chain BNC cables... but it's this termination thing that has me confused. Perhaps the big thread with Lavry will clear it up ...

Dinasti -- the reason for the add-on is because I want a 2 channel golden converter for most of my overdubs, something with some attitude. I've heard the 2192 has some good analogue vibe to it, or the Hedd has it's tape knobs. Something that I can stack tracks with and collect in subtle ways on. The aurora is great, but it's purely transparent, and whenever possible, I like vibe. I'm a vibe slut.

I've been back and forth with this a number of times over the last year (i think I've even posted about it) but ultimately I think I've made the decision that if I can't do tape, I want my conversion to be the best it possibly can be in the tape-ish direction.
Old 28th November 2006
  #11
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synthoid's Avatar
 

Quote:
but it's this termination thing that has me confused.
simply terminate the chain (as a whole) at both ends -- transmitting end and receiving end. The first and/or last device in the chain might provide internal termination. In that case, simply attach the BNC connector to it and enable the internal termination.

Have you considered getting a decent clock distributor, slaving it to the reference clock of your choice (either its own internal clock or else the clock of one of your converters), and distributing an individual clock signal to each piece of gear? Seems to me with so much nice gear, a clock distributor might be a reasonable investment.

-synthoid
Old 28th November 2006
  #12
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Yeah, that's the thread, thanks Max. If you look at the bottom of the page in any thread on PSW you'll see a link that says "generate printable PDF". You can just click that and you'll download a PDF of the entire thread that you can keep as reference.

That word clock thread, and the 384khz thread with some of the same people are two of the best and most informative discussions ever, in my opinion!

Also, here's an example of a properly working word clock chain from my studio. The termination is set to "off" except on the last (top) unit in the chain, when the termination is set to "on".
Attached Thumbnails
How best to clock: Let's separate fact from myth.-akairackrear.jpg  
Old 28th November 2006
  #13
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The Aurora is terminated (75 ohms) internally, you can't change it. I ran into some problems with sync using T-connectors until I put it last in my chain. It was also sensitive to the order you turned everything on, because the termination doesn't occur unless the unit is on, I believe.

That said, it has that "Synchrolock" technology, which is supposed to clean up the clock signal, so I'm told by Lynx support that it's ok to daisy chain it. In fact, they said daisy-chaining was the preferred method. Could just be marketing-speak that trickled down to tech support.

I'm fairly new to clocking multiple devices, so take my input with a grain of salt.

I had the following configurations working properly:

Mytek Stereo 96 --> Fireface800 (unterminated) --> Aurora8 w/ BNC T-connectors
Mytek Stereo 96 --> Aurora8 --> Fireface800 (75 ohm termination ON) daisy-chained

By properly I mean the Fireface registered Sync on all inputs and outputs and I didn't notice any glitches. I'm not sure how to tell otherwise.

The Mytek was feeding the Fireface via SPDIF, so it's a similar setup to what you're considering. It also worked to sync the system via:

Mytek SPDIF --> Fireface800 ADAT --> Aurora8

I didn't notice any differences between them sonically, but I never really listened for any changes.

Good luck.
Old 28th November 2006
  #14
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Chaining Wordclock..

Does that always work. The impression I get from my 1884 Tascam is the Word Clcok out is only the Tascam clock. If I set it to read an external Wordclock will it pass it through?

What about if I master it from a Mini-me using SPDIF? Does the wordclock output go silent then?
Old 28th November 2006
  #15
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heathen's Avatar
 

It's not that hard to work out really,if you have a device such as a mytek 8x 192 or an apogee big ben you will have multiple wc outs, if you have em use em. If you don't daisy chaining is the way to go it's simple, this is how the devices are disigned, wc out goes to wordclock in goes to wc out goes to wc in, final device is terminated.
Old 11th February 2007
  #16
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Downtown's Avatar
 

Wow...just stumbled upon this thread..

Hey guys. Just stumbled upon this thread and was very curious as to the outcome. I too am running an Aurora 16 and thinking about going to the FF 800 and eventually a 2192. I just wanted to know how clocking turned out as I too am slightly concerned and was debating on an external clock. Hopefully this won't get lost in the mess....
Old 11th February 2007
  #17
Tape Op
 
Larry Crane's Avatar
 

I didn't see anyone mention this, but for gear not terminated and without a switch, you can put a T connector on the BNC and a termination plug on one end, the other connect to the last piece of gear in the chain. Apogee has you do this to every BNC cable coming off a Big Ben or such. I had to order a bunch of T's and terminators a while back!
Old 11th February 2007
  #18
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Downtown's Avatar
 

Thanks for the tip Larry. I thoroughly enjoy Tape-Op, although the post in NY sucks!
Old 11th February 2007
  #19
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Quote:
Originally Posted by Jules View Post
But the problem with clock 'shoot outs'...... is the time it takes between each different set up, means you can 'forget' the sound of the last set up..
the way i've done it is stem some tracks out to a folcrom and add analog gear to taste. mult the output of the the last thing on the chain and treat mult 1 as 'original analog source'. mult 2 goes back into the DAW and recorded with whatever you're testing. play back is instantly A/B-able with 'original analog source', and everything is calibrated to .1dB.

the one that gets closer to the 'original analog source' in sound and stereo image wins, unless you like the sound of a particular piece, even if it's not accurate. but the constant is always the 'original analog source' and it's always instantly available.
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