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Author Topic: Audio Crackling DSS220 CAT745 Peter Maddock Film Handler Posts: 19 From: Benalla, Victoria, Australia Registered: May 2013 posted 02-10-2014 08:33 PM                    We have been experiencing severe intermittent crackling in our Dcinema system which is currently 5.1 although soon to be 7.1. The projector is a Barco DP2K 10S with Dolby DSS220, CAT745 IMB, and Dolby CP750. The problem can generally be corrected by manipulating the AES Audio Ethernet connection to the CP750. We have resorted to supporting this cable with masking tape to reduce the interference. Our installer says our upgrade to 7.1 should overcome the problem however we will then be using two Ethernet audio cables between the IMB and CP750, which seem to be the source of the problem. We are a single screen community cinema. Installer says the Dolby system has been installed in multiplex chains without problems. Anyone experienced this problem.  |  IP: Logged Jason Raftery Film Handler Posts: 72 From: San Diego, CA, USA Registered: May 2011 posted 02-10-2014 10:06 PM                     Does the CP750 display show the word "Discrete" intermittently dropping out as the crackling is occurring? Replace the Ethernet cables running from the IMB to the CP750--one or both of them is likely bad.  |  IP: Logged Carsten Kurz Film God Posts: 4340 From: Cologne, NRW, Germany Registered: Aug 2009 posted 02-11-2014 08:45 AM                     Yes, there have been a few reports of bad ethernet-audio cables on this forum earlier. How long is the connection between the projector/IMB and the CP750? Best is to convert to proper AES cabling as soon/short as possible. - Carsten  |  IP: Logged Dave Macaulay Film God Posts: 2321 From: Toronto, Canada Registered: Apr 2001 posted 02-11-2014 11:00 AM                     What do you use at the CP750 to go from ethernet to DB25? The Odyssey RJ-DB card has been good for us, and the 7.1 channel swapper card version does that job well. Plus, using high quality premade CAT6 cables is our normal practice: we have seen many problems because of faulty field termination of ethernet cables. We have not had any issues with the AES over CATx approach and I don't personally believe using "proper AES cables" will make any difference. You have some problem not inherent in using CATx cabling.  |  IP: Logged Sam D. Chavez Film God Posts: 2153 From: Martinez, CA USA Registered: Aug 2003 posted 02-11-2014 04:55 PM                       I've also had good luck with the Odyssey kit. AES cable is best for long runs though but expensive and not particularly convenient in this plug and play world where a lot of techs don't carry a soldering iron. (Probably for the best  |  IP: Logged Peter Maddock Film Handler Posts: 19 From: Benalla, Victoria, Australia Registered: May 2013 posted 02-11-2014 05:21 PM                    We have 10m of Ethernet cable between the DSS220 and IMB. We went for the Dolby system as it enabled connection to our remote projector which is mounted outside our bio box. The Doremi required a much shorter PCI Express cable. I am picking up a 7.1 card from the installer today and will speak to him about AES cabling. The Ethernet cable is connected to the CP750 via a RJ45/D25 adapter plug supplied by the installer. I am sure there would not be an inherent design problem with the Dolby Ethernet data connections. Thanks for the feedback on this problem. Peter  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 02-11-2014 05:24 PM                     I used AES up to about a year or so ago but use CAT 6 now in just about all installations. Not one issue and I have runs up to 30 feet long. Mark  |  IP: Logged Carsten Kurz Film God Posts: 4340 From: Cologne, NRW, Germany Registered: Aug 2009 posted 02-11-2014 05:27 PM                     We have a few discussions on the forum about this. While in general, CAT5-7 is suited for AES audio cabling, it seems that in real world scenarios it sometimes causes trouble, either by bad cables, screening, or simply the cable run is too long and the connected devices do not follow AES specs strictly . I also learned that large parts of the world still use unscreened twisted pair. As you now came up with a 10m run, I'm sure this is the problem. You may try a different/better cable, or switch to a different converter/cable combo as suggested by others. If you go 7.1., the dedicated Odyssey board with selectable signal routing for 7.1 and HI/VI is probably the best solution. - Carsten  |  IP: Logged Marco Giustini Film God Posts: 2713 From: Reading, UK Registered: Nov 2007 posted 02-11-2014 05:37 PM                     Despite the Ethernet not being the best for AES, the 745 does not have any issues with the it. If you have crackling noise you should replace your AES cable immediately - or check the connector, I guess the soldering may be faulty. You could install the ethernet cables straight away without waiting for the 7.1 upgrade.  |  IP: Logged Sam D. Chavez Film God Posts: 2153 From: Martinez, CA USA Registered: Aug 2003 posted 02-11-2014 07:12 PM                       The Odyssey Ethernet kit comes with two 35 Ft. Cat. 6 cables and I've had no problems with using that length but have not tried a longer run than that. I do like the the AES breakouts boards and had a bit to do with the design but this method has fallen from favor due to cost and the aforementioned problem with knowing in advance what the cable length will be.  |  IP: Logged Harold Hallikainen Jedi Master Film Handler Posts: 906 From: Denver, CO, USA Registered: Aug 2009 posted 02-11-2014 08:19 PM                        EBU3250E - AES/EBU Interface, Third Edition, 2004. States AEA/EBU may be carried over CAT5 cable for 400 meters unequalized and 800 meters equalized. Harold  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 02-12-2014 04:40 AM                     I believe, in the US and probably other countries, AES must use screened cable (shielded) or it will cause RF interference. We have had good luck with CAT cable for AES but also will still use proper AES cable, depending on the installation, environment, needs. We always make our own cables. I've had many more premade cable failures than our own.  |  IP: Logged Dave Macaulay Film God Posts: 2321 From: Toronto, Canada Registered: Apr 2001 posted 02-12-2014 07:02 AM                     I tried an RJ-DB adapter unit, it had a bunch of jumpers attached to the RJ45 that I plugged into the DB25 side. It worked OK for a while then they had issues with lost channels. I put in the Odyssey basic adapter and have had no problems since. I don't know what adapter your installer provided, but that's where I expect the problem could be. Swapping cables would be my first try, then losing that adapter if the cable change doesn't help. Doremi includes an adapter with their IMBs that I've used without trouble; it's just a pain because another cable has to be used to the D-A. The Odyssey card is simper and looks tidier.  |  IP: Logged Harold Hallikainen Jedi Master Film Handler Posts: 906 From: Denver, CO, USA Registered: Aug 2009 posted 02-12-2014 07:35 AM                        Of course, no adapters are required when driving a USL JSD-100 or JSD-60, since they have RJ45 AES/EBU inputs. Also, everyone agrees on the pin out of these connecrors, as opposed to DB-25. Harold  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 02-12-2014 01:16 PM                     Since we make our own cables...we just put on the DB25 right to the CAT cable...always works.  |  IP: Logged

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