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Author Topic: Dolby CP750 Surround Noise floor Marco Giustini Film God Posts: 2713 From: Reading, UK Registered: Nov 2007 posted 09-09-2009 05:47 PM                     Is there a reason, besides money, because a 2009 (but also a 2000) 10k euro processor must be so noisy? I remember doing tests on one of the 650 of my theater (software 2.2.sth), I could easily listen the noise floor disappearing from surrounds when pushing the "mute" button. It seems quite inadequate to me. What do you reckon?  |  IP: Logged Tony Bandiera Jr Film God Posts: 3067 From: Moreland Idaho Registered: Apr 2004 posted 09-12-2009 12:29 AM                     quote: Tony, When you pull out your CP-65, I'd be willing to take it off your hands at no charge! [Big Grin] Jarret, It would take someone like Zac Effron sleeping with me to give up my CP-65!! (That and a good amount of money.) It is a fully loaded 70mm ready model. IF it does get retired from my home room it will be safely preserved for some future use. I will have another CP-65 available soon, not as loaded as mine but in excellent condition (it's being pulled for a FILM digital upgrade to a CP-650.) I could cut you a good deal for it. OTOH, if I don't like it, there will be a CP-500 up for grabs soon. Marco: What are the gains on your amps set at? If they are wide open, it is no surprise that they are noticibly noisy. My guess as to why the surrounds have the higher noise floor has to do with the delay line used in the surrounds..my CP-65 is ever so slightly hissy in the surrounds as compared to the stage channels (I have a CAT150F card in it.) But NONE of the processors I have ever run into before are as bad as these CP-750's have been. I am going back there Monday and will report on any changes, but again time constraints may prevent the channel swap test.  |  IP: Logged Jarret Chessell Master Film Handler Posts: 288 From: London, Ontario, Canada Registered: Jan 2009 posted 09-12-2009 12:38 AM                     Sleep with Zac Effron and I get a free loaded CP-65?? I'll talk to Phil, I hear he's got an in to make that happen. It's looking more and more like we'll be replacing the Smart Mod 8 with our CP-55, probably adding a 441 and 222SR/A. If only popcorn machines could make money... and Zac Effron's.  |  IP: Logged John Hawkinson Film God Posts: 2273 From: Cambridge, MA, USA Registered: Feb 2002 posted 09-12-2009 09:17 AM                     OK, Tony, let's get quantitative. How bad is it really? Did you look at it on a scope? --jhawk  |  IP: Logged Tony Bandiera Jr Film God Posts: 3067 From: Moreland Idaho Registered: Apr 2004 posted 09-12-2009 01:31 PM                     John, since this was a d-cinema only install I did not bring my scope to the site. But I can say with confidence that the noise from the surrounds was AT LEAST 20-30db or more above the noise floor of the stage channels. (Which were for all perceptions dead quiet.) It was loud enough to make normal talking in that room very difficult to understand. Or to put it another way, it was audible behind the THX baffle wall behind the screen. This was not in any way a mild "standby" hiss.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 09-13-2009 06:09 PM                     Tony, I asked a local tech that has several 750s in their chain and he says that you probably have a defective unit. He has no such noise level in his surround channels. Mark  |  IP: Logged Tony Bandiera Jr Film God Posts: 3067 From: Moreland Idaho Registered: Apr 2004 posted 09-14-2009 09:57 PM                     Thanks Mark, that confirms my suspicions. That makes Dolby 0 for 2 on this job, I'll talk to my "boss" to get yet another unit.  |  IP: Logged

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