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sound system problems #482412 04/13/11 01:46 PM
Joined: Dec 2002 Posts: 9,429 Likes: 3 Beachwood jeffmoss26 Member
jeffmoss26 Member Joined: Dec 2002 Posts: 9,429 Likes: 3 Beachwood	We are having a weird problem at work...our auditorium system consists of a Mackie DX8 and 3 Crown Com-Tech 1600 amplifiers, all 70 Volt. If someone bumps the podium mic, or goes to plug a 1/8 inch cable into their laptop through a direct box, it will often cause a loud pop, then the system surges and shuts off. I can't figure out why or how to fix this, besides turning the channels all the way down when someone is plugging in. The devices in the rack are connected to power strips on 2 different circuits. Sometimes the breaker on the power strip will trip, but usually the breaker in the panel trips instead. Any ideas? Jeff Moss Moss Communications Computer Repair-Networking-Cabling MBSWWYPBX, JGAE

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Re: sound system problems #482413 04/13/11 10:09 PM
Joined: Sep 2005 Posts: 9,289 Likes: 11 Maine, USA metelcom Admin
metelcom Admin Joined: Sep 2005 Posts: 9,289 Likes: 11 Maine, USA	First off you should always have the volume off on empty inputs. What is shutting off? Is you direct box a passive device or does it have isolation? Have you checked the current load to make sure you are not overloading your circuits? Put and amp meter on the feed and monitor the current and see if it spikes when this happens. Merritt Business Telephones & Equipment + Commercial Audio/Video Products Commercial Communications . . . Turner, Maine If it was built after 1980 don't expect it to work right.

Re: sound system problems #482414 04/14/11 12:36 AM
Joined: May 2007 Posts: 5,058 Likes: 5 NYC Silversam Moderator-1A2, Cabling
Silversam Moderator-1A2, Cabling Joined: May 2007 Posts: 5,058 Likes: 5 NYC	Quote Originally posted by metelcom: First off you should always have the volume off on empty inputs. What is shutting off? Is you direct box a passive device or does it have isolation? Have you checked the current load to make sure you are not overloading your circuits? Put and amp meter on the feed and monitor the current and see if it spikes when this happens. Exactly! Sam "Where are we going and why are we in this hand basket?"

Re: sound system problems #482415 04/14/11 01:23 AM
Joined: Oct 2009 Posts: 410 Hills of PA Jim Bennett Member
Jim Bennett Member Joined: Oct 2009 Posts: 410 Hills of PA	I just took a peek at the manual for the Crown Com-Tech amps. Check out the current draw for a 1600 at 50% duty cycle [on page 43 on manual K-80636]. That "pop" when somebody plugs into a live input is easily equal to 50% duty... probably more! If these are the 120V units, it is close to 20 amps. If they run on 240V, it is only about 9 amps. But blowing the breaker is only a symptom. As others have said, you need to figure out how to stop people from plugging into inputs that are live. They have actually been lucky so far... Jim ************************************************** Speaking from a secure undisclosed location.

Re: sound system problems #482416 04/14/11 02:38 AM
Joined: Dec 2002 Posts: 9,429 Likes: 3 Beachwood jeffmoss26 Member
jeffmoss26 Member Joined: Dec 2002 Posts: 9,429 Likes: 3 Beachwood	Merritt, The breaker will trip thus shutting the mixer and amplifiers off. The direct boxes are passive, these are the ones we use: https://www.artproaudio.com/products.asp?type=90&cat=13&id=104 Jeff Moss Moss Communications Computer Repair-Networking-Cabling MBSWWYPBX, JGAE

Re: sound system problems #482417 04/14/11 10:01 AM
Joined: Jan 2010 Posts: 221 Likes: 1 NY tim10 Member
tim10 Member Joined: Jan 2010 Posts: 221 Likes: 1 NY	Those channels should be near off or completely off when plugging in or unplugging anything. Also check the level controls on those amps, you could try turning them down so the power to the system is not so high on those loud sounds. https://dedicatedpresentation.com/dukane-technical-support

Re: sound system problems #482418 04/15/11 10:39 AM
Joined: Feb 2005 Posts: 12,348 Likes: 4 New York hbiss Member
hbiss Member Joined: Feb 2005 Posts: 12,348 Likes: 4 New York	Sounds like you need a limiter to me... -Hal CALIFORNIA PROPOSITION 65 WARNING: Some comments made by me are known to the State of California to cause irreversible brain damage and serious mental disorders leading to confinement.

Re: sound system problems #482419 04/15/11 01:07 PM
Joined: Sep 2005 Posts: 9,289 Likes: 11 Maine, USA metelcom Admin
metelcom Admin Joined: Sep 2005 Posts: 9,289 Likes: 11 Maine, USA	Very good advice Hal that may even save the speakers. Merritt Business Telephones & Equipment + Commercial Audio/Video Products Commercial Communications . . . Turner, Maine If it was built after 1980 don't expect it to work right.

Re: sound system problems #482420 04/15/11 03:27 PM
Joined: Dec 2002 Posts: 9,429 Likes: 3 Beachwood jeffmoss26 Member
jeffmoss26 Member Joined: Dec 2002 Posts: 9,429 Likes: 3 Beachwood	The mixer does have all kinds of built in stuff through the software so I can try a limiter. I talked to Crown and they said at peak those amps can draw up to 13 amps. The way we have spaced out the power is with the wireless mics, one mixer, and 2 amps on one circuit, and another mixer, cd player and 2 more amps on the second circuit (the rack has equipment for 2 rooms in it) Unfortunately we only have 2 circuits for the rack, without putting in anything new. I should have the electricians come check with a clamp on meter when we are running it... Jeff Moss Moss Communications Computer Repair-Networking-Cabling MBSWWYPBX, JGAE

Re: sound system problems #482421 04/16/11 12:39 AM
Joined: Sep 2005 Posts: 9,289 Likes: 11 Maine, USA metelcom Admin
metelcom Admin Joined: Sep 2005 Posts: 9,289 Likes: 11 Maine, USA	If each amp can draw 13 amps at peak I think they should each be on a dedicated circuit. Have 2 new circuits run in for the mixers and other stuff. Merritt Business Telephones & Equipment + Commercial Audio/Video Products Commercial Communications . . . Turner, Maine If it was built after 1980 don't expect it to work right.