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Author Topic: Dolby Digital Sound Problem Mike Lauber Film Handler Posts: 19 From: Fond du Lac, WI, USA Registered: Nov 2002 posted 07-06-2004 10:34 PM                     I suddenly am having a problem with the sound in one of our Dolby Digital Theatres. The center channel sounds fuzzy and crackly throughout the entire movie. The rest of the channels sound fine. Is this likely a problem with that amp? The Digital Processor shows it's reading the digital track fine. It just started happening today, so I haven't tried any other prints, but it did it through the trailers and all reels. Thanks in advance for any help.  |  IP: Logged Richard Hamilton Phenomenal Film Handler Posts: 1341 From: Evansville, Indiana Registered: Jan 2000 posted 07-06-2004 10:41 PM                     How does the movie sound in "bypass" mode, or SR, or mono? If it sounds the same, I would suspect a blown speaker. What kind of amps and speakers? Since you said it happened during all of the previews and all reels, it's not a print problem. Rick  |  IP: Logged Mike Pennell Expert Film Handler Posts: 150 From: Tucson, AZ, USA Registered: Apr 2003 posted 07-06-2004 10:43 PM                     Possible bad amp, speaker, high frequency diaphram, or loose connection. Check your wires coming out of the amps and into the speaker and make sure they are tight. Hows the dialog sound? Real Bassy? then check your diaphram. You could try trading the outputs between either left/right and center to check the amp. Make sure you mark them and put them back correctly.  |  IP: Logged Mike Lauber Film Handler Posts: 19 From: Fond du Lac, WI, USA Registered: Nov 2002 posted 07-06-2004 10:47 PM                     It sounds poor out of the Amplifier Monitor Speaker too, so I don't think it could be the speaker. I haven't tried it in bypass or in SR at all yet, but I will later tonight. The dialog doesn't sound bassy, just fuzzy.  |  IP: Logged Rick Long Jedi Master Film Handler Posts: 759 From: Toronto, Ontario, Canada Registered: Nov 1999 posted 07-06-2004 10:55 PM                     Try the re-set button on the Dolby if your unit has that feature. Otherwise, exchange the wiring for the left and centre amps to see if the problem travels.  |  IP: Logged Richard Hamilton Phenomenal Film Handler Posts: 1341 From: Evansville, Indiana Registered: Jan 2000 posted 07-06-2004 11:12 PM                     Can you listen to processor output on the monitor speaker?  |  IP: Logged Mike Lauber Film Handler Posts: 19 From: Fond du Lac, WI, USA Registered: Nov 2002 posted 07-07-2004 01:35 AM                     Yeah, you can on the monitor, but for some reason nothing comes through when I listen to it on 'processor'. It used to always work fine, and it still does in our other dolby digital theatre.  |  IP: Logged Richard Hamilton Phenomenal Film Handler Posts: 1341 From: Evansville, Indiana Registered: Jan 2000 posted 07-07-2004 01:39 AM                     How does it sound in different formats? What kind of processor, monitor, amps and speakers? Rick  |  IP: Logged Steve Scott Phenomenal Film Handler Posts: 1300 From: Minneapolis, MN Registered: Sep 2000 posted 07-07-2004 02:13 PM                     What processor are you using? Is this a DA10/DA20 or a CP500D/CP650D, or some other combination? You may need to do some modification to the cards to eliminate the problem, expecially if it's high frequency distortion.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 07-07-2004 03:16 PM                     Since the problem wasn't there before it is something that has failed so modification isn't the needed reedy but repair I find it odd that also sudenly the monitor has no signal present when in monitoring processor out mode My bet is that the speaker has had an issue and is damaged Is the system Biamped Try as Rick sujested to play in analogue and see i the problem persists  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 07-07-2004 08:19 PM                     Actually Dolby has had quite a few mods that can be done in the field to the DA-20 / CP-500. In fact the latest CP-500 Dolby mod is to eliminate random clicks heard in all the channels on some CP-500s. We did have one customer that had bad problems with clicks and the mod solved the problem in all the processors Its caused by a bad clock. Most mods however are done only by Dolby because it involves software and can only be had by purchasing a new revised board for what ever it may be. Mark @ CLACO  |  IP: Logged Mike Babb Master Film Handler Posts: 250 From: Norwich UK Registered: Jul 2002 posted 07-08-2004 04:02 AM                        I've heard this type of thing with a bad gain pot on the amp, the tests suggested above should sort it out for you if so.  |  IP: Logged Dean Kollet Jedi Master Film Handler Posts: 591 From: Florida State University Registered: Jul 2003 posted 07-09-2004 12:27 PM                     I don't know if you are using a Dolby Analoq processor as well, but we had the same problem last night running a movie. The fix that usually helps me (and I don't know if you are set up this way) is to shut the entire sound rack down and pop our our crossover cards and put 'em back in. It has helped 9 times out of 10, loose connections kill you. More info on your equipment will help a lot too...  |  IP: Logged

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