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Author Topic: Dolby CP55 help Tom Wise Film Handler Posts: 8 From: Nottingham, Notts, UK Registered: Jan 2011 posted 01-03-2011 12:11 PM                     Hi, A friend of mine has recently taken over a small cinema and asked me to take a look at the sound system. Following an initial inspection of the gear I noticed that the backplane of their CP55 had been modded. My background is in the pro-audio industry (live bands etc.) so I have a good idea what most of the equipment does, however my knowledge of cinema-specific kit is limited, so I was hoping someone here may be able to assist me in identifying what exactly has been done to the unit. Fullsize image (c.567kB) After some brief Googling on the subject it looks like there are a few mods available for CP55's, although none that I have found seem to match what has been done to this unit. I understand that some mods require changes to the cards, which I didn't know or think to check last time I was there. I can go and take photos of these as well if the attached photo is not enough to go on. Any assistance or links to information would be gratefully received. Many thanks in advance, Tom  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 01-03-2011 12:46 PM                     The red wire in your drawing is for the Cat 222SR/A modification. The non-red wires (could be gray, could be white) are for the Cat 441 modification found in the DA10 or DA20 manual. -Steve  |  IP: Logged Sam D. Chavez Film God Posts: 2153 From: Martinez, CA USA Registered: Aug 2003 posted 01-03-2011 12:48 PM                       The CP55 backplane has been modified to install a Cat. No. 441 in place of the 241. The point of this mod is to allow stereo surrounds as well as an external subwoofer input for use with SR.D and/or DTS/SDDS.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 01-03-2011 12:53 PM                     Jeeez Sam, you're slow! The most scary thing on this CP55 are the bypass relays...they are the cursed STC white relays...known the world over for dropping out signals. Reference Dolby Field Bulletin 161. -Steve  |  IP: Logged Tom Wise Film Handler Posts: 8 From: Nottingham, Notts, UK Registered: Jan 2011 posted 01-03-2011 01:29 PM                     Steve & Sam - many thanks to you both for the quick responses and invaluable information. I will try and absorb the manuals before going to have another look at the system. It's an exciting learning curve! @Steve - thanks also for the tip-off about the relays. Any chance you could point me in the direction of FB-161? I couldn't find it in the Equipment Manual Warehouse. Tom  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 01-03-2011 02:22 PM                     Tom, FB161 predates the fancy schmancy PDF world...however, I suspect that you might see it appear in the up coming weeks...just a hunch. -Steve  |  IP: Logged Tom Wise Film Handler Posts: 8 From: Nottingham, Notts, UK Registered: Jan 2011 posted 01-03-2011 05:36 PM                     Hi Steve, Thanks, I'll keep an eye out for it... Tom  |  IP: Logged Sam D. Chavez Film God Posts: 2153 From: Martinez, CA USA Registered: Aug 2003 posted 01-03-2011 06:37 PM                       Steve, It's earlier out here and you hadn't yet posted when I began my thoughtful reply so excuse me.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 01-03-2011 08:15 PM                      |  IP: Logged Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 01-05-2011 12:19 AM                     Guess nobody noticed FB161 was added to the warehouse yesterday.  |  IP: Logged Kenneth Wuepper Phenomenal Film Handler Posts: 1026 From: Saginaw, MI, USA Registered: Feb 2002 posted 01-05-2011 07:30 AM                     Hello Brad, I caught it in the header for newly added posts. Even though there was a warehouse additions header in the original page, this is a more complete listing feature. Thanks KEN  |  IP: Logged Tom Wise Film Handler Posts: 8 From: Nottingham, Notts, UK Registered: Jan 2011 posted 01-05-2011 03:27 PM                     Thanks Brad. I was actually out at the cinema yesterday so didn't notice the new file. I'll give Dolby a call and see if I can get some replacements before the STC's give up. As for the CP55, turns out it has neither a Cat 241 or 441 installed, so I guess that means no stereo surrounds, even with the backplane modification. Another thing to add to the shopping list... Tom  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 01-05-2011 07:07 PM                     Yep, no stereo surrounds, no subwoofer and no "EQ" on the mono surrounds you have left. Good luck on the STCs...This is a bulletin that dates back about 25-years. Dolby has formally announced the discontinuation of support for the CP55 (and the other analog processors except the CP45). A good (better actually) substitute relay is an OMRON G5V series. It is a 24VDC relay. They make three relays in that model and voltage...the difference is the coil resistance. It shouldn't matter which you use...the lower current relays taxing the 24V rail just a bit less. -Steve  |  IP: Logged Tom Wise Film Handler Posts: 8 From: Nottingham, Notts, UK Registered: Jan 2011 posted 01-06-2011 05:22 PM                     Hi Steve, Many thanks for the relay info. I guess that trying to obtain a new Cat 441 card from Dolby is also going to be a dead-end. Apart from the Classifieds board here at Film-Tech, are there any other potential sources of cards for these old processors? Alternatively, are the schematics available?! I can live without the EQ as it can be done further down the signal path, but the lack of split surround and sub outputs is a bit of a problem. Does the lack of a subwoofer mean that the L, C & R channels are not being delivered in full-range (i.e. are the LCR outputs high-passed to cross-over with the subwoofer)? Sub-question: Is this the case whether a Cat 241/441 card is installed or not (i.e. does the removal of the card switch the main outputs to full-range)? Apologies for going off-topic. I can start another thread if this is deviating too much from the original thread title. Tom  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 01-06-2011 05:58 PM                     The stage channels are always full range the sub foroptical is properly called optical bass extension(OBE) and is the sum of the Lt and Rt from the optical preamp it is passed through a filter and a downward expander and then a parametric eq  |  IP: Logged

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