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Author Topic: CP500 Output Distortion and Panel Meter Glitches Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 09-23-2016 08:08 PM                     Did you use star washers on the mounting screws to the rack?  |  IP: Logged Marco Giustini Film God Posts: 2713 From: Reading, UK Registered: Nov 2007 posted 09-24-2016 04:56 AM                     As I said there were a number of technical bulletins for the 500. To be honest the 500 has always been infamous for not being the most reliable piece of equipment - in term of those little glitches you experienced. Others may have more experience than me but if this happens every now and then I wouldn't be too much concerned. There may be a fix for your very problem but I am not sure, I know that my 500's were suffering the same issue but very rarely.  |  IP: Logged Tom Ostertag Film Handler Posts: 41 From: St. Louis, MO, USA Registered: Jun 2014 posted 09-25-2016 03:46 AM                     quote: Gordon McLeod Did you use star washers on the mounting screws to the rack? Hmm, I did not. I was under the impression they only recommended those to avoid ground loop-related audio issues like hum, buzz, etc., but now I see the note in the manual about avoiding "electrical noise" as well, so it's probably worth a shot! I am, however, using a round-hole rack with clip nuts, so the ground connection through the rack screws to the rack itself isn't exactly guaranteed. Perhaps a ground wire from the CP500 chassis bolted to the rack frame would work better. quote: Marco Giustini ...if this happens every now and then I wouldn't be too much concerned. That's what I'm starting to accept. It would be great to not have to worry about it though. It seems like the issue only happens when I'm trying to show off my system and impress guests, but isn't that always the way? Oh well, it's no big deal. If I come up with something that magically works, I'll let you all know!  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 09-25-2016 09:56 AM                     Are you sure the distortion isn't that channel of the power amp failing? I still see this happen way more often than actual processor failures. Mark  |  IP: Logged Tom Ostertag Film Handler Posts: 41 From: St. Louis, MO, USA Registered: Jun 2014 posted 09-26-2016 02:57 AM                     That was one of my suspicions after I heard the distortion for the first time. Well, after I ruled out a blown HF compression driver, which it really sounded like at first. But no, the issue is audible quite clearly from my MS-100 booth monitor, while monitoring processor outputs. When preparing to power-cycle the CP500, I do shut down the amps first, and the distortion persists from the booth monitor until the CP500 is rebooted. All is good after that. The distortion has happened on L, Rs, and C channels in that order, which each use different amplifiers. My L/C/R channels are bi-amped, and the distortion is audible from both the HF and LF channels together.  |  IP: Logged Sam D. Chavez Film God Posts: 2153 From: Martinez, CA USA Registered: Aug 2003 posted 09-26-2016 10:25 AM                       I would not discount the possibility of your setup oscillating. I had trouble with is unless there is at lest one connection from the low side of the Power Amp to the - or ground connection on the monitor. Once it starts ringing it will show up all over the place. Rebooting the 500 breaks the path but it comes back as you've stated.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 09-26-2016 02:42 PM                     I had odd motor boating issues with CP-500's & Crown amp's a long time ago, but that turned out to be improper wiring from the Strong factory where a ground loop had been built into the factory harness in each console... Mark  |  IP: Logged Marco Giustini Film God Posts: 2713 From: Reading, UK Registered: Nov 2007 posted 09-26-2016 04:25 PM                     indeed, make sure it's definitely the processor and nothing else before giving up It shouldn't happen very often though. As I said it was a very rare occurrence - every several months approximately.  |  IP: Logged Tom Ostertag Film Handler Posts: 41 From: St. Louis, MO, USA Registered: Jun 2014 posted 09-29-2016 09:27 AM                     quote: Sam D. Chavez I would not discount the possibility of your setup oscillating. I had trouble with is unless there is at lest one connection from the low side of the Power Amp to the - or ground connection on the monitor. Very interesting issue! I don't actually have the booth monitor connected to the power amp outputs. This is my home setup, so I can easily walk out of the booth and listen to the speakers. I also wanted to maintain as much isolation as possible between the power amps and the monitoring, for reasons like you mention! There are also distribution amplifiers between the processor and power amps, that also provide an isolated feed to monitoring. The booth monitor is not paralleled with the amps. I did that, in part, so that I could patch different sources directly into the booth monitor for troubleshooting purposes, without altering the signals or line termination to the amps in any way. These distribution amps have been thoroughly verified, but if the distortion happens again, I'll disconnect them and verify from the back of the processor itself. The sound of the distortion sounds very much like it's happening in the digital domain before it hits the analog output chain. I've never heard this sort of "bit crusher" type effect as a result of analog circuitry or grounding issues. I won't rule anything out based on that assumption though. If (when) it happens again, hopefully it'll be when I have enough time to break things apart and test individually.  |  IP: Logged

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