Topic: Lazy AES3 -> BNC for v3+722 sync?

[it-goes-to-eleven]

Gotta a show tonight where'd I'd like to sync clocks but I don't have any 110ohm coax and I'm not optimistic about finding any locally.

I know the impedance should be 110ohms but I'm thinking of just taking a 75ohm BNC coax cable and soldering an XLR on the end. The run could be as short as 12" but I don't want to bother if this isn't likely to work. Thoughts?

Thanks!

[gratefulphish]

From some of the prior discussions here, I belive that you can just use the S/PDIF out of the V3, into the 722, and manually set the input on the 722 to anaolg.  The clock signal then gets transmitted via the cable, which can probably be basic 75 ohm, as opposed to AES, and a light in the display on the 722 shows "L" I believe, to indicate that it is working off an external clock.  Then all you need is a BNC>RCA adapter (Just a plug) rather than building a cable.

[gratefulphish]

Now, I am theorizing, and you may want to call Neal at Grace on this, but if the V3s jumpers are set to consumer, then the AES one output is essentially S/PDIF, as well as the coax out.  If you have an XLR>RCA, you can probably do what I suggested in the prior post.  Should be able to set it up and try it out at home, before you head to the gig.

[Brian Skalinder]

Now, I am theorizing, and you may want to call Neal at Grace on this, but if the V3s jumpers are set to consumer, then the AES one output is essentially S/PDIF, as well as the coax out.

Per the manual:

The V3 has a total of three digital output connectors:two
balanced XLR 110 Ω outputs and one coaxial 75 Ω output..In addition,V3 preampli fiers with
the optical out option have a standard Toslink optical output jack.All connectors are active
whenever the A/D converter is on.The AES1 and S/PDIF outputs both transmit consumer or
professional format data while the AES2 connector always transmits professional format data.
See the jumper con figuration section of this manual for details.

So while the AES1 digital output may deliver a S/PDIF format (instead of AES/EBU format), it's still balanced XLR 110-ohm, not 75-ohm.

[gratefulphish]

Brian, I was aware of what you posted, and I also know that to properly convert 110 Ohm to 75 Ohm, you really need an expensive converter box, to do the job properly.  But while researching that issue, it seemed that the "budget method" was to use an XLR>RCA cable that would reduce the output.  This results in some truncation of the audio signal, but what I was suggesting in my post, was that it might still pass the clock signal from the V3.  Don't know for sure, and I have not tried it.  I did run my new four channel setup, linking the V3 wordclock to the 722, which worked fine, but I need to work with the MT some more.  It was my first outing with it, and I got the media full message on a brand new, formatted card.  Then it would go into record, and then stop.  Need to work with it at home a little.

[JasonSobel]

and I also know that to properly convert 110 Ohm to 75 Ohm, you really need an expensive converter box, to do the job properly.  But while researching that issue, it seemed that the "budget method" was to use an XLR>RCA cable that would reduce the output.  This results in some truncation of the audio signal, but what I was suggesting in my post, was that it might still pass the clock signal from the V3.

actually, all you need is a small transformer to convert from 110 ohm down to 75 ohm.   it's $20 here (the first on the page, aka the "BCJ-XJ-TR"):
http://tinyurl.com/2b797o

now, a lot of people just use a straight XLR>RCA cable.  and that'll work for short runs, but it's not ideal (although it has nothing to do with truncation of the audio signal).  but without the tranformer, you've got an impedance mis-match, which will cause reflections of the signal inside the cable, which, in turn creates jitter.  now, on shorter runs, the jitter created won't be too much and the signal will probably still lock.  but for $20, I say go for the transformer