Film-Tech Forum ARCHIVE: AES DB-25 switcher

This is topic AES DB-25 switcher in forum Digital Cinema Forum at Film-Tech Forum ARCHIVE.

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Posted by James Larden (Member # 5594) on 02-08-2010, 03:09 PM:

Hello,

We're currently looking to acquire d-cinema capability in two of our cinemas. If we install a DMA8+ does anyone know if there is an available switcher so that we can share the DB-25 input; to switch from the AES output of a d-cinema server to the disembedded AES audio from HD-SDI sources such as HDCAM.

Thanks

Posted by Steve Guttag (Member # 268) on 02-08-2010, 05:19 PM:

Got money?

The SDI audio de-embedding is simple. http://www.blackmagic-design.com/products/miniconverters/. Black Magic Design makes some of the best SDI converters I've ever dealt with.

The SDI to Audio will output it in AES3 (balanced) so it will be ready for the DMA8 (once you make your TRS to DB 25 cable). As for switchers...now you are into some money.

There are AES switchers...they are typically expensive and often 4x1 and and $500-$700 a pop. You can go the cheap route and just get a DB25 A/B switch and pray that the digital integrity will not be too compromised going through it (AES3 is based on a 110-Ohm impedence...a cheap passive A/B switch will have single conductor wires inside). You could build a patch bay of your own with DB25 connectors...experience has shown though, that Dsubs do not fare well with many repeated plugs/unplugs (particularly male plugs). You could put in an AES rated patch bay...again, not cheap.

But lets look at this a bit...on your HDCAM...since you are looking to de-embed...I'm thinking you have a JH3 or similar deck. 95% of all HDCAM tapes are 2-channel...the other 5% have something funky on the 3/4 tracks like Dolby E. Why not save yourself a lot of grief and money...let the DCinema keep the Digital 1 to itself and let Digital 2 or three work with the HDCAM...if you need the Dolby-E track on 3/4 (if it exists) then move the TRS plug on the de-embedder over...pretty simple and you've spent far less money.

Steve

Posted by James Larden (Member # 5594) on 02-09-2010, 11:33 AM:

Much obliged,

I already discarded the DB-25 A/B switcher solution for the reasons you listed. If cost was no object could one install a cat.790 card into a CP-650 while using a DMA8+ as well, thus having two balanced AES DB-25 inputs?

Posted by Steve Guttag (Member # 268) on 02-09-2010, 12:59 PM:

bzzzt...the Cat 790 uses unbalanced inputs. You could use a converter to make them balanced (either in-line transformers or the Odyssey products 650-OPTIO-AES) The Cat 778 uses balanced inputs...BUT it kills your analog outputs so you only have AES outputs too.