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Author Topic: "Robosound" on a CP-750? Jim Cassedy Phenomenal Film Handler Posts: 1661 From: San Francisco, CA Registered: Dec 2006 posted 08-27-2016 08:43 PM                     I got a call from a theater today that they had to cancel a show and move a movie out of their big auditorium due to some strange noises coming out of the surround speakers. I went down there and there was definitely a lot of distortion and a low 'garbling' sound coming out of the surrounds, especially during one of the trailers that had a lot of surround info. Surrounds were silent if playback was paused, or when the CP-750 was switched to an analog or non-sync input. Pink noise & the 'thump track' out of the 750's internal generator were OK too. Since the noise was especially obvious during one of the trailers, I put that trailer into "loop" mode and the more I listened to it, the more the offending audio began to sound a bit similar to the familiar "robosound" that sometimes happens with a CP-650. I finally shut EVERYTHING down, including some equipment they usually leave on 24/7. While powered down, I also pulled & re-sat all the digital & analog connections between the (Christie) projector, CP-750 processor, amps, etc. After this, and a complete re-boot, sound was OK. I 'looped' that trailer and watched it at least a dozen times at higher-than-normal volume. Then re-loaded their playlist for today and watched all their pre-show stuff and the first 20min or so of the feature, and it was OK. So, I'm not sure what it was- - but as I said, it had more of a 'digtal problem' sound to it than some analog issue. But I've never had a problem with any of the CP-750's I've encountered. They've had two shows since I did the "repair" earlier today, and all is still good. Any ideas, anyone? I hate it when I "fix" something and I'm not sure of the exact cause. And, I'm leaving for my annual projection gig at the Telluride Film Festival tomorrow, so I'm hoping whatever I did stays "fixed" for them, at least till I get back.  |  IP: Logged Mike Olpin Chop Chop! Posts: 1852 From: Dallas, TX Registered: Jan 2002 posted 08-27-2016 09:24 PM                     Sounds like the D/A went a little wonky and simply needed a power cycle. Do you use the 750's internal D/A or do you use an external D/A and then come from that into the EXT input? I'm surprised the theater called out their tech before doing a simple cycle on the sound equipment.  |  IP: Logged Jim Cassedy Phenomenal Film Handler Posts: 1661 From: San Francisco, CA Registered: Dec 2006 posted 08-28-2016 08:35 AM                     Hi Mike- In answer to your question- - the audio at this location is handled by the 750's internal D/A circuitry. I'm not surprised they called me. They were in 'panic mode', and operate with a bare-bones staff, so taking someone off the floor, even to do something as mundane as a re-boot, would have been a problem for them. That's how I make 'the big bux' LoL! >U at Telluride this year? I remember meeting you there a couple of years ago. This is my 10th year there.  |  IP: Logged Carsten Kurz Film God Posts: 4340 From: Cologne, NRW, Germany Registered: Aug 2009 posted 08-29-2016 05:50 AM                     Sometimes, noise from the surrounds can be an indication of a dying CP750 power supply. I know a few places where this has been the case. - Carsten  |  IP: Logged

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