Feedback Problems

avkid

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Fight Leukemia
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Feb 17, 2004
Location
Lakewood, NJ
have any stray power cable laying around?
 

wolf825

Senior Team Emeritus
Premium Member
Joined
Apr 7, 2003
Location
Eastcoast USA
blademaster said:
Down here in tucson ive got a problem with a low feedback problem that coming out of nowhere. no outside power except our monitor amp. im wondering where in all of nine hells its comign from
Please describe the problem in more detail, including your system set up, when you noticec the "feedback" and how you control it or not. Feedback is a frequency problem that loops in a sound system and grows exponetially in volume very quickly, and will continue to increase until its halted by either cutting off mains or channels volumes...however if you are experiencing or describing a low-freq hum--which could be a power or ground issue, this will be constant "noise" or electrical sound, around 60hz and not increase in volume exponentially on its own and may be noticible more when other electrical items in your facility are turned on or used (like AC handlers and heaters etc). So please explain a bit more in detail so we can gladly help you out.

-w
 

blademaster

Active Member
Joined
Mar 17, 2005
Location
Mountain Home, AR
Mainly the problem is when i briong the house up to zero im hearing it.
The set we have is a sanctuary with decent acoustics running with 2 cardoid uni driectional mic(phantom powered) for the choir with EV15-2 house speakers and unfortunately I ahve yet to get down and figure out the equalizer spec other than 20 band or what type of main amp we got. No stray power cable laying around. But I do agree with wolf825 that it is actually hum more than feedback
 

avkid

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Feb 17, 2004
Location
Lakewood, NJ
Basically you should have more than one ground for your panel
 

DJErik07

Active Member
Joined
Nov 13, 2004
Location
MA/ NC

DJErik07

Active Member
Joined
Nov 13, 2004
Location
MA/ NC
Thanks forgot the name!! Just on eof those brain freezes :)
 

BNBSound

Active Member
Joined
Mar 17, 2005
Location
Alexander, NY
Oh MAN! Please, please, PLEASE do NOT use one of those adapters. They are unsafe and illegal, as per the National Electrical Code. Not that they'll cart you off in cuffs, but if someone gets zapped they'll be looking for the guy who plugged that thing in.

If you must lift the ground on your system it should be a last ditch effort and there are safe ways to do it. If there's no other way, then you can use a GFCI (Ground Fault Circuit Interrupter). And you'll have to use one at each location you want to lift the ground, amp racks, mix, pit, all of em.

You can buy heavy duty, construction rated GFCI adapters and cut the ground pins off of them. That's acceptable. Another option is to change the regular duplex outlets that your gear plugs into to GFCI outlets and not hook up the ground wire. But you must use the "No Equipment Ground" stickers that come with the outlets. And lastly, you can build a little device on the cheap for just a simple spot ground lift of a single device like a guitar amp or console. Get a cord from a hair dryer or similar appliance that has GFCI protection included, cut it off and install a three prong recepticle on the other end.

GFCI is the ONLY safe and legal way to lift the equipment ground. If you don't get it, don't do it. Talk to someone who does get it. Read my post in the "What Went Wrong" forum "The things you learn the hard way" and find out how 54 volts AC can accidentally get into someone's dental work if you're not careful about grounding.

And lastly, lifting the ground via GFCI's is the last thing you should do, becuase they tend to trip a lot and you have to stop what you're doing and go reset them. If there's hum in the system, it quite likely comes from using unbablanced lines. If all the channel inputs on your cosole are filled with XLRs then you should see a significant reduction in hum. If you need to get a couple devices on DIs to get balanced signal then do it. If it turns out that your power system is at fault, get the staff to fix it or get them to hire an electrician to fix it. And lastly, if the problem is not with faulty or incorrect wiring, it might just be dirty power from large motors elswhere in the building. If that's the case you could have an electrician move the circuits that your audio plugs into to the other bus bar in the panel and see if that helps.

Just please, Please, PLEASE be safe!
 

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