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Author Topic: CP-750 Analog Input Wiring Jim Cassedy Phenomenal Film Handler Posts: 1661 From: San Francisco, CA Registered: Dec 2006 posted 08-21-2013 10:07 AM                     I wasn't sure if this should go in the FILM or DIGITAL forum, so I tossed a coin . . . . . . . and it wound up here: I've got a situation where a theater wants to get their 35mm projector running again. (D'oh! I KNEW this was going to happen! I've been getting a lot of these requests lately.) Fortunately, the digital installers did not follow the "scorched earth" digital conversion policy I've seen so many times here in CA. I'll deal with getting the projectorthingy running again, but my question has to do with resurrecting the audio. The audio chain is intact from the 35 projector to their old CP-45. I was thinking I could come off the outputs of the '45 and go into the 25pin analog input on the back of the CP-750. I've already made up the neccessary cable & tested it yesterday. I was able to get sound. . . sort of. Of course the EQ and levels were all over the place, and as I walked around the auditorium I could here severe 'phasing'. When I got home, I double checked the CP-750 documentation, and it appears that the pin-out for the analog input connector is shown differently on two different pages. Here's one diagram (slightly re-formatted to fit here). Page 15, Fig 2.2 But, on Page 69, Table 7.8 below shows totally different pin-ous: Also, is it me, or does one diagram seem to show single-ended and the diagram other balanced connections? WHICH ONE IS CORRECT ? (Fortunately, I used a crimp-pin DB-25 instead of the solder connection one Dolby supplies with the '750 so re-arranging the pins won't be too difficult! )  |  IP: Logged Sam D. Chavez Film God Posts: 2153 From: Martinez, CA USA Registered: Aug 2003 posted 08-21-2013 10:23 AM                       I would go with the picture. I have done this before and it works. The list must be wrong or mislabeled. I am doing a project with the same issue, connecting the 45 output into a USL-60.  |  IP: Logged Jim Cassedy Phenomenal Film Handler Posts: 1661 From: San Francisco, CA Registered: Dec 2006 posted 08-21-2013 10:33 AM                     Thanks, Sam. I used the "table" when I made up my cable. I knew something was wrong! I'm flying into Telluride on Saturday, so I guess I'll see 'ya there.  |  IP: Logged Alexander Alves Film Handler Posts: 33 From: Diwanman, Vasai, India Registered: May 2003 posted 08-21-2013 10:50 AM                     The CP-750 analog inputs are balanced. The manual you are referring to may be old.  |  IP: Logged Carsten Kurz Film God Posts: 4340 From: Cologne, NRW, Germany Registered: Aug 2009 posted 08-21-2013 04:40 PM                     My CP750 rev4 manual shows the same discrepancy. The first diagram shows the 'old' unbalanced analog Dolby D25 pinout as used on previous processors, like the DA20 or the CP650 ext analog in. Maybe some sort of a copy/paste mistake or a late spec change. Good to see Dolby finally acknowledged the benefits of full balanced connections in a high level listening environment. Took them quite a while. Now only if it is true... - Carsten  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 08-22-2013 05:22 AM                     I want to say we used the balanced wiring on the input of the CP750 without issue but I won't swear to that. But, generally, we look for the pinout tables when we make up our cables. -Steve  |  IP: Logged Scott Norwood Film God Posts: 8146 From: Boston, MA. USA (1774.21 miles northeast of Dallas) Registered: Jun 99 posted 08-22-2013 07:22 AM                        It should be the same as the DMA8+ output (balanced). I have used a straight-through DB25 cable from the DMA8+ to a couple of CP750s and had no issues. If I remember correctly, the channel assignments on the CP750 input are configurable in software (at least among common options).  |  IP: Logged Carsten Kurz Film God Posts: 4340 From: Cologne, NRW, Germany Registered: Aug 2009 posted 08-22-2013 07:52 AM                     There are multiple other parts in the CP750 documentation explicitly referring to balanced analog multichannel inputs and balanced multichannel analog outputs. Strange... Did Dolby make a switch at some time, as with the DMA8 to DMA8+ to facilitate interfacing with the CP650/DMA8+ class of devices with 1:1 cables? Are there 'old' CP750 in the field and CP750+? - Carsten  |  IP: Logged Jim Cassedy Phenomenal Film Handler Posts: 1661 From: San Francisco, CA Registered: Dec 2006 posted 08-22-2013 03:47 PM                     quote: Alexander Alves The manual you are referring to may be old. Exactly! - The manual I was originally referring to came off of the Dolby extranet website, and is apparantly very out-of-date. (D'oh!) I think it was an "Issue Vers 3". I went down to a theater that recently 'went digital' & talked them into letting me borrow the documentation disk that came packed in the box with their new CP750. It's an "Issue 5" and they've changed the pin-out pictorial diagram so that it agrees with the pin-out table elswhere in the manual. I found one or two other discrepencies between the manuals too. I copied the new manual offa the disk, & deleted the old one I had on my computerthingy.  |  IP: Logged Carsten Kurz Film God Posts: 4340 From: Cologne, NRW, Germany Registered: Aug 2009 posted 08-22-2013 07:22 PM                     Jim, could you make this rev5 manual available to me? I have a rev4. Unfortunately I can not email you through the forum. - Carsten  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 08-23-2013 05:58 AM                     Issue 5 is on the Dolby Secure site AND a DA20-CP750 pinout table in a separate document.  |  IP: Logged Steve Moore Expert Film Handler Posts: 211 From: Leeds, West Yorks, UK Registered: Apr 2008 posted 08-23-2013 11:18 AM                     I've just done the same thing with my CP750 and the output of a CP65. The cabling for the analogue in (multi channel in) is the same pin numbers as the output ones... the plan being that if your CP 750 failed you could still plug the output of the CP(55/65) straight to the amps... (plug the male and female D25 together and bypass the 750) If you use the pin numbers for the output in the 750 manual as a reference for the pin numbers for the input that should be the same.  |  IP: Logged

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