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sfaudiogeek
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#1
13th October 2006
Old 13th October 2006
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Word Clock Distribution

Hey all!

I am putting together the wiring plan for my new studio, and have a question regarding word clock distribution. I have an Apogee Big Ben as my master clock, in the control room of my studio, which has 6 word clock outputs. One output is being used to clock Pro Tools, which leaves me with 5 outputs. However, I need to route WC to 20 outputs that will be in various different panels throughout my studio, mostly in other rooms than the CR. In order to do this, do I need a dedicated word clock distribution amplifier such as the Drawmer D-Clock, or can I just patch the outputs to a BNC patchbay and route the patchbay's outputs to the panels? Is there a maximim distance that WC signals can travel?

Thanks for any help!
#2
13th October 2006
Old 13th October 2006
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since no one else has answered i'll volunteer my inexpertise. if by PT you mean digi 192 interfaces, they are terminated so always have to be at the end of the chain. for things like apogee converters BNC T connectors will work fine. as to other gear you want to sync i wouldn't know.

referring to safe WC distance i understand the shorter the better, so i try not to have anything longer than 3m. but i'd also like to know from the experts out there what a safe limit would be assuming you have good quality cable.
#3
14th October 2006
Old 14th October 2006
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You can't use a BNC patchbay because the impedance of WC has to be at least 75Ohm otherwise it will not sync properly. The WC outputs of the Big Ben are 75Ohm each so it's not possible to split the WC signal. You need a Word Clock Distribution Amplifier like the Drawmer D-Clock or a Sonifex RB-DDA6W.

cheers,
Peter
#4
14th October 2006
Old 14th October 2006
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Hi,

I just saw your post on rec.audio.pro and I came over here to look up a relevant thread I recently posted to ;-)

BNC Cable & Word Clock termination
BNC Cable & Word Clock termination


I've never had a Big Ben or tried this with the Lucid GENX6 I used to have but it should work to run each of the six outputs of your Big Ben to groups of three or four devices that are connected together with 75 ohm T's and terminators.

I would try this first because it will save you a bundle of $$$ and if it doesn't work for you you'll only be out probably less than $20 for the T's and terminators (you'll still use the same cables.

Keep in mind :
keep distances short
if your devices have 'auto terminated' word clock inputs you'll need to turn the auto-term off, or if you can't, put these units as the last device in the chain
if you have an auto terminated device at the end of a chain, make sure that it is powered up, otherwise the other devices in the chain may not work

Best of luck!


Note : the Lucid CLKX6 and GENx6 have been discontinued so snap them up now if you think you'll need one. (usually from $200 to $400) There is one on Ebay right now
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sfaudiogeek
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17th October 2006
Old 17th October 2006
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Word Clock Distribution

OK so I guess I should clear some things up. . .

I am setting up a new studio that will have a few different rooms--a CR, a main live space, and two iso booths. I will also have panels in various random hallways and staircases. Each of these rooms will have one to four panels in it, and I want BNC connectors on each panel to enable the musicians to bring in a piece of digital gear and be able to connect it to/sync it up with my master clock (Big Ben) which resides in the control room. So not each panel has to actually be running WC through it at all times, which is why I thought about using a patch bay. I have found a few BNC patchbays with 75 Ohm connectors on both sides such as: http://home.flash.net/~motodata/patchbays/digital.html--it's toward the bottom of the page. So could this be used? I am thinking that each panel would be permanently connected to a connector on the patch bay, then I would send out the WC from the Big Ben and connect to whichever panel we want to use at that time.

Does this make sense? I can't use T connectors because not all the gear will be in the studio at all times, and not all of it will live together in the control room either. I am trying to figure out a way to send out WC to various different locations in a studio without getting dropouts.
#6
18th October 2006
Old 18th October 2006
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If I were going to try to do this, I would think of using repeaters to shore up the signal. In other words (budget considerations aside), distribute from a central BB to a secondary BB (or other word clock generator) in the room where the musicians are. They will plug into the secondary BB. You are begging for problems of skew and jitter by having long runs and consequent attenuation, further degradation through a patch bay, etc.

-synthoid
#7
18th October 2006
Old 18th October 2006
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WC connections should be direct and short - 'direct' meaning no daisy-chaining if you can avoid it and 'short' meaning on the order of 10 feet or 3 meters or less. I try to keep WC runs as short as possible (a couple feet or less - I make my own cables) and always make sure WC connections are properly terminated ONCE.

For longer runs use AES

AES is a better clock source than WC in most cases because you have not only the frame and sample clock, you have the bit clock.

I always use AES for a reference if the device I want to lock to it can accept that - and most everything does.

Since I am almost always installing an AES router of some sort I have a means of distibuting AES via the router. If you want to send AES to another location and get back to WC you can use one of a number of boxes that take in AES and output WC.
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18th October 2006
Old 18th October 2006
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Quote:
Originally Posted by klett View Post
For longer runs use AES
but if you send both clock and audio through the same cable (AES) doesn't this degrade the sound? thank you.
#9
18th October 2006
Old 18th October 2006
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hey guys,

while you're talking abt word clock distributions, may i jump in and borrow the thread?..

anyway,my WC devices are SYNC I/O, 192 I/O, TASCAM DM-3200 and DA-88.

I should be asking this at duc, but i thought I'll try here too..

SYNC I/O is loop-synced to 192 I/O
SYNC I/O WC out to TASCAM DM-3200

Question 1
so should i connect the DA-88 to 192 I/O WC OUT or DM-3200 WC OUT?

Question 2
and do i still need a BNC T-joint with 75ohm terminator at the DA-88's INPUT?

Question 3
If you're familiar with the TASCAM DM-3200, on the WC connection, there's a WC IN and the OUT can be used as THRU. and also a switch to enable / disable 75 ohm termination on the input. which should I use?

THANAKS!
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18th October 2006
Old 18th October 2006
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Quote:
Originally Posted by raal View Post
but if you send both clock and audio through the same cable (AES) doesn't this degrade the sound? thank you.
I believe he may have been refering to AES reference clock, which is an additional AES signal on a separate cable and separate XLR connectors, not the same signal as the AES digital audio signal. Not all gear has AES Ref Clock inputs & outputs in addition to the AES digital audio I/O, but if you got it, it's a good choice.

DP
#11
18th October 2006
Old 18th October 2006
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I would get premium cable and goor T connectors. Try that first. It's cheaper and IMH far better within reasonable cabling distances.
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#12
24th October 2006
Old 24th October 2006
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Quote:
Originally Posted by raal View Post
but if you send both clock and audio through the same cable (AES) doesn't this degrade the sound? thank you.
nope, mastering guys do this all the time, lock to source... in fact some prefer this to providing a master clock at all...

AES signal connections are designed with an embedded clock. Presence of audio does not impact the performance of the AES connection as a clock source.

Last edited by klett; 24th October 2006 at 01:19 PM.. Reason: clarity
#13
24th October 2006
Old 24th October 2006
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Quote:
Originally Posted by klett View Post
nope, mastering guys do this all the time, lock to source... in fact some prefer this to providing a master clock at all...

AES signal connections are designed with an embedded clock. Presence of audio does not impact the performance of the AES connection as a clock source.
FWIW I haven't verified it one way or another but I've read that doing this can possibley introduce a little more jitter into the clock signal.
#14
24th October 2006
Old 24th October 2006
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Quote:
Originally Posted by ImJohn View Post
FWIW I haven't verified it one way or another but I've read that doing this can possibley introduce a little more jitter into the clock signal.
i've read that too... urban myth?

question for mr. klett: if the receiving device has no AES, only S/PDIF I/O and WC I/O is it preferable to use both these, or would you send everything S/PDIF, as you would with AES? thank you.
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