Film-Tech Forum ARCHIVE: Splitting AES audio?

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Posted by Magnus Eriksson (Member # 6085) on 06-25-2015, 02:45 PM:

Setup: DSS200/Cat745, DMA8+, CP650/Cat790, amps/speakers wired for 7.1.
Theatre (art house) running DCP, 35mm SR/SRD/DTS and all video stuff you can Think of.
They want DCP to play 5.1, 7.1 and prologic from AES 1/2 and be able to adjust audio delay on the fly (when screening home made DCP:s)
Until now they only use DMA8+ for this (with a desktop computer permantly connected), but now they want to add 7.1.
My idea is to split AES 1/2, 3/4 & 5/6 and play 7.1 on the CP650 and the rest through DMA8+.
But; what is the best way of splitting? Is it a "safe" way to go?? What contraptions do I need for a proper matching of levels/impedance???
I have done a similar setup (in the same Town actually), but there I had a AP20...

/M.E.

Posted by Stephan Shelley (Member # 8587) on 06-25-2015, 04:21 PM:

That is the way I have done it. Odyssey products makes all the adapters to do the job of 7.1 on the 650.

Posted by Magnus Eriksson (Member # 6085) on 06-25-2015, 04:56 PM:

I have one of these Odyssey. A snake 4xRCA -> DB25 plus a DB25 with 2xRJ45. A lot of connectors already.
Then adding a "branch" to the DMA8, well, I don´t know [uhoh]

/M.E.

Posted by Stephan Shelley (Member # 8587) on 06-25-2015, 05:53 PM:

I would run a pair of cat 6s to the 650 with this board http://www.odyssey-products.com/products/circuit_boards/dolby_processors/cp650/option_i_o_boards_files/stacks_image_4498 .jpg and the 16RJ-7.1-DSDY board that has 2 rj-45 connectors to DB 25 and puts AES 11 & 12 on AES input 7 & 8 for 7.1 also has a connector for HI/VI on the side. In most cases you will need an D to A converter for the HI/VI if you need it.

Posted by Harold Hallikainen (Member # 5405) on 06-25-2015, 09:35 PM:

On splitting AES/EBU, I made a resistive splitter that maintained 110 ohms on each port. I use it to have a server drive two sound processors (one for normal operation, one in development). If that's what you need, I can post a schematic tomorrow. Someone may make this as a product, though. I did this with three RJ45 connectors, one in and two out.

Harold

Posted by Magnus Eriksson (Member # 6085) on 06-26-2015, 03:41 AM:

I miss a board for CP650 with two RJ45 and internal channel routing. That would have been useful.
@Harold: Yes, please send me the schematic. That can give me some inspiration.
What about impedance and balanced/unbalanced inputs. CP650 and DMA8+ are different.

/M.E.

Posted by Carsten Kurz (Member # 5396) on 06-26-2015, 05:59 AM:

There are passive, transformer based multichannel AES Splitters available, if you're concerned about mixed impedance/termination schemes.

- Carsten

Posted by Magnus Eriksson (Member # 6085) on 06-26-2015, 06:18 AM:

quote: Carsten Kurz
if you're concerned about mixed impedance/termination schemes.

Well, yes, I am. I've had my share of issues with AES to CP650. But not since I applied 'cable discipline' and 2.3.7.2 DO NOT SHIP fw.

Posted by Steve Guttag (Member # 268) on 06-26-2015, 06:20 AM:

I would caution in a CP650 application with the CAT790 that the CAT790 is not the most stable of AES decoders...it is easily tripped up and also is a 75-Ohm input device rather than 110-Ohm and is probably more fussy about the voltage of that signal too. I suspect the more one deviates from providing a clean/stable well-formed signal the greater the likelihood of ROBOSOUND. Note, the CAT778, when IS 110-Ohm input hasn't had the Robosound problems of the CAT790 but it also forces AES output too instead of Analog.

Quite a few devices nowadays seem much more tolerant of out-of-spec AES signals (voltages and impedances) that may be giving some folks an "anything goes" felling that will likely bite you when you it would be most embarrassing and will be quoting lines like "I done this lots of times and never had a problem before). Since digital works until it doesn't, people don't have a real feel for just how close to the cliff they really are in their practices.

Posted by Stephan Shelley (Member # 8587) on 06-26-2015, 09:32 PM:

Magnus why do you need to send the AES signal to both the 650 and DMA8+? The 650 can do all the formats need from the cinema server. 88 for 5.1, 91 for 7.1 and you can use 80 to do a prologic decode on a two channel output. Only thing it can not do is Dolby E but I doubt you will be getting that from a cinema server. Save the DMA 8+ for other digital sources.

Posted by Magnus Eriksson (Member # 6085) on 06-28-2015, 08:28 AM:

Format 80, is that AES 1/2 prologic? I guess I missed that [Embarrassed]

Anyhow, there is also a button issue here. Buttons 05 & 10 are locked. With 5.1, 7.1, prologic, 05 & 10 there are 3 buttons left. The projectionists want to have quick access to NS1 (analogue video), NS2 (auditorium mixer), mic and 11 (DMA8).
An alternative would be to connect the auditorium mixer to 'film' on the DMA8 (DTS isn´t used that much)
/M.E.

Posted by Stephan Shelley (Member # 8587) on 07-01-2015, 09:47 PM:

would you need to use all those formats in one day? The formats are easy to program to a button so you set it up for the formats used that day or show.

As far as the DTS they made some pass through switching cards for when one had a DA20 as well as the DTS and also for the CP200. One could adapt one of them for the auditorium mixer much like for a DA20.

Posted by Ian Freer (Member # 1940) on 07-02-2015, 02:43 AM:

Are there any channel routing options in the Dolby server?

On a GDC or Doremi you can create custom channel maps; if this is available on the Dolby could you do the following;
On AES 1-8, have 1-1, 2-2, 3-3, 4-4, 5-5, 6-6, 11-7, 12-8. This gives 7.1 to one device
On AES 9-16; have 1-9, 2-10, 3-11, 4-12, 5-13, 6-14, 11-15, 12-16. This gives at least the L-R to the DMA8+ for pro-logic, and provides the full set of channels if you turn off the pro-logic decode.

Then each Ethernet cable/adaptor off the IMB connects to it's own device. No splitting needed, no patching etc...

Neither the CP650 or DMA8+ can take more than 8 channels, so I'm guessing you're not utilising HI/VI-N? If you are, the above routing may cause issues...

I've only done basic installs with Dolby so never needed to investigate this, so apologies if I wasted your time...

Cheers,
Ian

Posted by Steve Guttag (Member # 268) on 07-02-2015, 05:31 AM:

No. Dolby servers do not allow for custom audio routing.